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Thread: Overvoltage question

  1. #1
    Gordon Misch's Avatar
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    Overvoltage question

    I have a Plane Power alternator and voltage regulator and Odyssey battery. Beginning last May I started getting over voltage indications of 15-16+ volts. I would pull the field breaker, wait till the battery voltage declined into the upper 11's, then reset. All would be fine until the battery was fully charged again. Over the last several months the problem has become more frequent, and recently the overvoltage crowbar has tripped the field breaker a few times. I suspected a poor connection somewhere, but found none. I have ordered a new Plane Power regulator.

    My question, that just occurred to me this evening - could an old battery cause this problem? My battery is 10 years old, but seems to hold charge well and cranks the engine well.

    Before I simply install the new regulator, voiding its returnability, I'd appreciate opinions from you folks. Thanks!
    Gordon

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  2. #2
    irishfield's Avatar
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    Not sure on the plane power wiring, but 9 times out of 10 overcharging is a ground issue, as in the voltage regulator not well grounded. If it's a two field alternator, having one wire break off the voltage regulator will = runaway full field voltage. Check for a perfect ground on the voltage regulator case... zero ohms case of regulator to case of alternator.

  3. #3
    Gordon Misch's Avatar
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    Thank you. I did check the regulator ground wire at the regulator terminal. I measured between 0.1 and 0.2 ohms. (My Fluke meter zeros at 0.1 ohm.) The Plane Power troubleshooting guide specs 0.1 ohms, I believe (it's been a few days since I read it). I will check reg case to alt case tomorrow.
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  4. #4
    hotrod180's Avatar
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    If it was me, I'd change out that 10 year old battery just because.
    I had some electrical issues earlier this year, changed out my 5 year old Odyssey just because.
    A cheap way to eliminate a possible issue. Or what could become an issue before long.
    Turns out the problem was the regulator going haywire.
    But I don't regret changing out the battery.
    Cessna Skywagon-- accept no substitute!

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    When you check the crimps on your connections push and pull on them. I had a gremlin I chased for 2 years, it was a crimp that allowed the cable to slide forward so when you would tug on the wire it would reseat and feel good. It would hold for a while them get loose again.
    DENNY
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  6. #6
    wireweinie's Avatar
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    Look at the diagram for the Plane-Power system. The wire coming from the field circuit breaker provides power to the regulator, at the 'enable' position. There is also a jumper wire from the 'enable' position to the 'sense' position, where the voltage is monitored. A poor or intermittent connection anywhere along this circuit will cause incorrect voltage output from the system. And keep in mind that this circuit should also run through one pole of the master switch, if wired correctly, although this is not shown on the Plane-Power diagram.

    To do a basic trouble shoot of this circuit, turn on the master switch and make sure the charging system is powered on (engine does not need to be running here). With a digital voltmeter, measure bus bar voltage. Now measure the voltage at both terminals of the field breaker and the master switch (field power side only). Then measure the voltage at the 'enable' and 'sense' terminals on the regulator. Note ANY change in voltage from bus voltage. This will tell you what component or section of wire that is causing issue. A poor connection or any high resistance, such as a corroded breaker or switch, will cause the regulator to see a lower voltage and cause the regulator to increase the systems output voltage.

    Another trick I use for these installs is to run the ground wire from the regulator to the alternator case. It's not that common, but this will eliminate any ground issues that might exist between the alternator and the airframe.

    Web
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  7. #7
    wireweinie's Avatar
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    Trying for a better copy of the diagram.

    Web
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  8. #8
    wireweinie's Avatar
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    Found a better diagram. This time it has the field circuit routed through one pole of the master switch.

    Web
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  9. #9
    Gordon Misch's Avatar
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    Thank you much. I will double check crimps and voltages as suggested. What's odd is that voltage is well regulated at 14.3 or 14.4 until the battery is fully charged. Then it starts to spike in a non-smooth manner - i.e. the voltage hops around erratically from 16+ back to 14.2. If I leave it alone it eventually crowbars out. If I pull the field breaker and let the battery run down just a bit, then upon re-energizing the field the system regulates properly again.

    I will follow through with your suggestions today. If that all seems correct, will see how the new regulator behaves.

    This all began at the same time I discovered a loose connection on the "downstream" terminal of the master relay (Thank you, Steve of Steve's Aircraft for helping me discover that). So I wonder if the regulator might possibly have been "spiked" by that in some way.
    Gordon

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  10. #10
    Gordon Misch's Avatar
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    Well, I wiggled the wires at crimps, measured resistance to ground, and voltages as suggested. Each of those things seems right. Then flew for a little while and the system behaved. So - - I'll keep watching it, and install the new regulator, assuming the system continues to be erratic.
    Gordon

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  11. #11
    wireweinie's Avatar
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    Is your regulator ground wire tied to the firewall or did you route it to the back of the alternator case? Cycle the field circuit breaker and master switch rapidly to break up any corrosion or burnt spots on the contacts. You've got a poor connection somewhere. Replacing the reg won't fix that.

    When you do voltage checks, keep the ground lead from the meter connected to the same point for all checks. And be aware that even .1 volt drops will cause issues on a sensing circuit. I.e. bus bar voltage is 11.8. Voltage measured at the output terminal of the breaker is 11.6. This means that at operation,when the bus voltage is actually 14.2 volts as per the regs setting, the reg will only see 14.0 volts and try to increase the alternator voltage.

    To make matters worse, a fixed resistance produces a higher and higher voltage drop as the current in the wire increases. Example; .8 ohms resistance will produce a drop of .2 volts if the current flow is .25 amps. If the reg senses an under voltage and increases current flow to .75 amps, the voltage drop will be .6 volts. So the greater the current draw the more inaccurate the sensing circuit becomes.

    Web
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  12. #12
    Gordon Misch's Avatar
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    Thanks Web, all of that makes sense to me, at least in principle. A couple thoughts:

    The system has worked fine for 10+ years, until this summer. So it's wired correctly.

    My regulator is 10 or 11 years old, and there is no "sense" terminal connection like shown on the schematic. That terminal location is labeled "N/C" on the face of the regulator and nothing is connected to it.

    Compared to Buss voltage of 11.9 V, with field energized, I measured a 0.1 V drop at the "Enable" terminal of the regulator. Then I measured an additional 0.1 V drop at the "Field" terminal of the regulator. That seemed reasonable to me given that there is field current through that circuit?? My Fluke low impedance meter has a 0.1V resolution, so each of those could be .05V in error.

    Alternator and regulator ground terminals are both independently routed to a ground buss which is in turn grounded to the airframe. Those ground paths measure 0 ohms.

    Again, when the battery is less than fully charged, the system reliably regulates correctly (14.3 - 14.4 V). It's only when the battery is peaked (around 12.5V, in flight, radio etc turned on, with the field breaker pulled) that it gets goofy.

    Am I still missing something? Thanks again for your help!

    Edit: Alternator case to ground is about 7 or 8 ohms. I discounted that, assuming that the alternator ground terminal is all that really matters. Am I wrong about that?
    Gordon

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  13. #13
    wireweinie's Avatar
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    Can you post a pic of the regulator and it's label? Never seen one without the sense terminal.

    What size wire is used as the alternator ground? If the alternator case shows 8 ohms resistance to ground, it doesn't make sense that the alternator ground wire shows 0 ohms to ground as the ground wire is connected directly to the case. Maybe post a pic of the alternator case where the ground wire is connected? Should be 0 ohms from the alternator to the engine, from the engine to the airframe, and from the airframe to the ground post on the battery.

    Web
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  14. #14
    Gordon Misch's Avatar
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    Gordon

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  15. #15
    Gordon Misch's Avatar
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    This is the only pic I have right now. I will go over to the airport and try to get a better pic and answers to your questions. Thanks again...
    Gordon

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  16. #16
    Gordon Misch's Avatar
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    Ok, well, I have egg on my face. Again.

    1. I did NOT measure from an alternator ground post to ground. I measured from the ground terminal on the regulator, and that runs about 0 to 0.2 ohm, depending on how I hold my mouth. I'm referencing from probe wedged between copper primer line and firewall, and confirming with probe jammed into braided engine / mount strap, and from ground post on firewall. If I reverse the probes, it changes slightly - I have no idea the why on that. But my conclusion overall is about 0.1 ohm.

    2. Alternator case to ground reference is about 0.8 ohm, not the 8 I previously stated.

    Perhaps a good next step would be to wire directly from regulator ground terminal to the alternator case?

    Here is a better pic of the regulator.
    Last edited by Gordon Misch; 10-14-2020 at 07:57 PM.
    Gordon

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    wireweinie's Avatar
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    Humor me. Run the ground wire on the reg, to the ground stud on the rear case of the alternator. You want 0 ohms between the reg and alternator.

    Web
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  18. #18
    Gordon Misch's Avatar
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    Yep, will do tomorrow. Thanks!

    I assume you mean to retain the lead from the reg ground terminal to airframe ground, and add a new one to alternator frame?

    Edit: As has been said so many times, nowhere else can one get such timely, friendly, expert advice. I sure do appreciate.
    Gordon

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  19. #19
    wireweinie's Avatar
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    If you run the reg ground wire to the alternator case, you can skip the reg ground to airframe. You should take a moment to clean up the engine grounds or add a good braided ground from the crankcase to the airframe.

    The engine to airframe ground is hard to check for resistance. Any primer line or p-lead ground will measure low resistance but when you crank the engine, all that current needs a large ground path to return to the battery.

    Web
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  20. #20
    Gordon Misch's Avatar
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    Got it. I'll check them and clean as necessary. I have a large braided ground and a smaller 8 awg ground, each from crankcase to airframe but separate paths, like Mike MCS recommends. It seems as though the alternator frame might not be well bonded to the engine case. I'll see what I can do to check that also. Thanks again.
    Gordon

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  21. #21
    BC12D-4-85's Avatar
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    Also try charging the battery off the airframe. Look for unexpected voltage excursions as the AGM reaches charge. Takes 14.5 VDC plus to condition them. Them = several for me. They can become sulfated and resist charge via internal breakdown at + voltage.

    Gary
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  22. #22
    hotrod180's Avatar
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    Quote Originally Posted by DENNY View Post
    When you check the crimps on your connections push and pull on them. I had a gremlin I chased for 2 years, it was a crimp that allowed the cable to slide forward so when you would tug on the wire it would reseat and feel good. It would hold for a while them get loose again.
    DENNY
    I had charging issues on my last airplane.
    Took the alt off to take it down to auto-electric shop for testing.
    Checked out good.
    When I reinstalled it, I had to twist one wire to get it on the terminal.
    I noticed that while the crimp-on ring connector pushed & pulled OK,
    it turned freely on the wire.
    Cut the connector off & crimped on a new one...problem solved.
    Cessna Skywagon-- accept no substitute!
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  23. #23

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    Had a similar problem. Turned out to be a ground issue. Whomever mounted the alternator used vibration dampeners and the ground ran through the tension adjustment bar. Somewhere along, the adjustment bar broke but still held under tension and a safety wire. It failed finally showing arcing across the broken section. It did not have a separate ground wire to the back of the case. All kinds of testing resulted in confusion because of intermittent readings, which resulted in disassembly. Did me a favor, and is corrected as mentioned above with ground wire directly to regulator.
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  24. #24
    Gordon Misch's Avatar
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    Well, I added a wire from alternator frame to ground terminal on regulator. The skin on the back of my hand is rearranged but.... Flew it for about an hour and a half and the voltage remained steady at 14.2 - 14.3 the whole time. So I think it might be fixed. Thanks all and especially to Web. You were right on sir!
    Last edited by Gordon Misch; 10-15-2020 at 09:24 PM.
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  25. #25
    Gordon Misch's Avatar
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    Flew another hour and a half or so today and the voltage never wavered. Happy!
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  26. #26

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    Charging issue



    The video shows the Fluke meter connected direct to battery + and - while the Milwaukee Meter is connected to the Alcor Regulator ground and the alternator field terminal. There are two loads on I believe in the video with the "Alternator"/Field switch ON.

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    Experiencing Charging Issues:
    Alcor Motorolla Alternator 12 VDC 55 Amp
    InterAv Over Voltage Regulator P/N 635-62448
    Alcor Motorolla Regulator P/N ?

    Background on how I arrived at the issue in case it sets off any light bulbs for folks:
    I performed an oil change the other day when I had a lapse in judgement and got a bunch of oil all over the place. To make clean up slightly less frustrating, I got out solvent and spray gun and figured while at it the engine could use a spray dow, etc. Thinking there is some relationship here to my issue as there was no issues prior to oil change. After solvent spray down, plane sat for 18-20 hours before taking short 30-40 min flight yesterday. Returned from short 30-40 min flight (did not observe/notice deflection of ammeter during flight- my mistake) but upon return to the airfield I noticed some audible tone/draw in my headset coinciding with the strobes. After shutdown, I thought I would check to see what was going on so I went to fire up the plane again (not entirely sure the logic behind firing up again but I attempted) and battery had been drained during flight. This battery is only 2 years old and my master relay and starter solenoid were replaced at the same time. I do not suspect there is any issues with those components.

    So, I put the battery on the charger and left it overnight while I began my investigations into conductor continuity, terminals, crimps, etc. Nothing abnormal found during installation confirmation check. Aside from the dedicated conductor between the alternator and the voltage regulator, my setup is identical to the included wiring diagram/schematic. This morning I did a resistance check between my voltage regulator ground and the alternator ground terminal and found there to be 0.0 ohms resistance. I then confirmed that the Overvoltage relay positive (+) was reading the same as bus bar voltage when my master switch was on, which it was. I then checked the voltage at the field terminal on the alternator as well as at the regulator and noticed there was a voltage difference between the OVR positive(+) and the reading at the field terminal on the alternator and regulator. 12.9 or so on the OVR (+) and 4-6 VDC at the alt & reg field terminal. Keep in mind the engine is not operational during these tests. Is this expected? Should the Over Voltage Relay alter the voltage to the alternator and regulator field terminal ? If so, what is the required voltage at the alternator field input for viable operations? Assuming that it is to be somewhere in the 4-6VDC range, what would be the next place to investigate and isolate the potential suspect component? I did the same steps above while engine was running at approx 6-800 RPM and obtained the same readings.

    Measure voltage at the regulator post on the alternator during engine operation? Not really sure at the moment.

  27. #27

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    Update:
    I removed the original field connection at the alternator, then ran a jumper from battery to field terminal on alternator and observed +30-35 ammeter deflection so can somewhat confidently remove from doubt the alternator. Now just to determine if I’m in for replacing the OVR and Voltage regulator with something new or if I can determine if I can overcome with current setup. Any input as to ruling out OVR or VR as culprit is appreciated.

    Quote Originally Posted by bjh356 View Post


    The video shows the Fluke meter connected direct to battery + and - while the Milwaukee Meter is connected to the Alcor Regulator ground and the alternator field terminal. There are two loads on I believe in the video with the "Alternator"/Field switch ON.

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    Experiencing Charging Issues:
    Alcor Motorolla Alternator 12 VDC 55 Amp
    InterAv Over Voltage Regulator P/N 635-62448
    Alcor Motorolla Regulator P/N ?

    Background on how I arrived at the issue in case it sets off any light bulbs for folks:
    I performed an oil change the other day when I had a lapse in judgement and got a bunch of oil all over the place. To make clean up slightly less frustrating, I got out solvent and spray gun and figured while at it the engine could use a spray dow, etc. Thinking there is some relationship here to my issue as there was no issues prior to oil change. After solvent spray down, plane sat for 18-20 hours before taking short 30-40 min flight yesterday. Returned from short 30-40 min flight (did not observe/notice deflection of ammeter during flight- my mistake) but upon return to the airfield I noticed some audible tone/draw in my headset coinciding with the strobes. After shutdown, I thought I would check to see what was going on so I went to fire up the plane again (not entirely sure the logic behind firing up again but I attempted) and battery had been drained during flight. This battery is only 2 years old and my master relay and starter solenoid were replaced at the same time. I do not suspect there is any issues with those components.

    So, I put the battery on the charger and left it overnight while I began my investigations into conductor continuity, terminals, crimps, etc. Nothing abnormal found during installation confirmation check. Aside from the dedicated conductor between the alternator and the voltage regulator, my setup is identical to the included wiring diagram/schematic. This morning I did a resistance check between my voltage regulator ground and the alternator ground terminal and found there to be 0.0 ohms resistance. I then confirmed that the Overvoltage relay positive (+) was reading the same as bus bar voltage when my master switch was on, which it was. I then checked the voltage at the field terminal on the alternator as well as at the regulator and noticed there was a voltage difference between the OVR positive(+) and the reading at the field terminal on the alternator and regulator. 12.9 or so on the OVR (+) and 4-6 VDC at the alt & reg field terminal. Keep in mind the engine is not operational during these tests. Is this expected? Should the Over Voltage Relay alter the voltage to the alternator and regulator field terminal ? If so, what is the required voltage at the alternator field input for viable operations? Assuming that it is to be somewhere in the 4-6VDC range, what would be the next place to investigate and isolate the potential suspect component? I did the same steps above while engine was running at approx 6-800 RPM and obtained the same readings.

    Measure voltage at the regulator post on the alternator during engine operation? Not really sure at the moment.
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  28. #28
    wireweinie's Avatar
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    Power on, engine off, what is the voltage on the field terminal on the regulator and at the field terminal on the back of the alternator? Any difference indicates a problem with the OV module, master switch, or wiring. The 'over voltage module' is just a relay that opens at a specific voltage.

    This is an Interav charging system. If you have to replace ANY component, replace the system with a Plane-Power system. You'll never look back.

    Web
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  29. #29

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    6.9ish volts on both regulator field and alternator field. Bus voltage = battery voltage when master switch “ON”

    I disconnected the field terminal conductor at the alternator, then took ohm reading between the disconnected alt field wire and regulator field to test resistance between the two for investigating OVR issues. Reading was 0.3 ohms.

    After the above, I bypassed the OVR by connecting Regulator field directly to alternator field and observed no charging or load carrying.


    Quote Originally Posted by wireweinie View Post
    Power on, engine off, what is the voltage on the field terminal on the regulator and at the field terminal on the back of the alternator? Any difference indicates a problem with the OV module, master switch, or wiring. The 'over voltage module' is just a relay that opens at a specific voltage.

    This is an Interav charging system. If you have to replace ANY component, replace the system with a Plane-Power system. You'll never look back.

    Web

  30. #30
    wireweinie's Avatar
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    Most likely a bad regulator. Here's a troubleshooting guide from an old InterAv manual. Hope this helps. (Psst! Plane-Power SAL12-70 kit, just sayin')

    Web
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  31. #31

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    Wireweine saves the day and perseverance prevails!

    Because this site is worth it’s weight in gold! Wireweine’ comments from years ago in addition to the a Recent interav document he supplied me with gave me confidence there was nothing wrong with
    my setup and that I needed a better ground between regulator and alternator. Once I tested that further I was able to reproduce and solve my issue. New conductor between regulator and alternator and now happy once again. Maybe my solvent spray down the other day dislodged some conductive something or another. After a full day of chasing my tail I’ll be sure to keep and eye on this one.

    Happy 4th Everybody!
    My baby gets some papa time for the 4th due to some perseverance and this website!
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    Quote Originally Posted by wireweinie View Post
    Most likely a bad regulator. Here's a troubleshooting guide from an old InterAv manual. Hope this helps. (Psst! Plane-Power SAL12-70 kit, just sayin')

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  32. #32

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    Glad you got it working. Not clear though on your fix, did you reground both the alternator and regulator? My regulator is grounded where it is bolted down, alternator grounds to the engine mount I think.

    The 6 volts field you mentioned had me thinking bad regulator, the only time field voltage gets down that low is when its charging than it goes way down below bus voltage, testing without the alternator on it should be near bus voltage.

  33. #33

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    The regulator was originally grounded via a machine screw (white conductor in photo below) that served as a mounting hole for the regulator itself. For 5 plus years this had not been a problem. It was theoretically grounded through its contact with the firewall. Not sure what exactly changed however that caused this to stop working. During my review of the wiring diagram I noticed my install slightly differed from the drawing. That difference being the ground for the regulator. In drawing it shows conductor “B” between regulator and alternator. When I removed original reg ground and instead connected a new conductor to the same ground that alternator uses, I resumed normal Ops. Wireweine supplied a troubleshooting doc for voltage measurements that my readings all came back as normal. I was using the ground terminal of the battery when taking my readings and that gave me the idea to find a better ground for regulator.
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    Quote Originally Posted by Eddie747 View Post
    Glad you got it working. Not clear though on your fix, did you reground both the alternator and regulator? My regulator is grounded where it is bolted down, alternator grounds to the engine mount I think.

    The 6 volts field you mentioned had me thinking bad regulator, the only time field voltage gets down that low is when its charging than it goes way down below bus voltage, testing without the alternator on it should be near bus voltage.

  34. #34

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    That makes sense you ran a wire from the ground on the regulator to the neg terminal on the alternator, your regulator was not grounded, now it is. That 6.9 volts on your field still puzzles me, that should be 12 volts or battery voltage until your alternator is on and charging.

  35. #35
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    Voltage from this reg will never be at bus voltage during operation.

    The field of an alternator is just a coil that produces a magnetic field that is proportional to the amount of current (amps) flowing through it. The regulator is called that because it regulates or controls that field current flow. The regulator also forms a series circuit with the field coil. In a series circuit the current flow is the same in all components but the total voltage is divided among each component. The resistance of the field coil will never change since it is a fixed coil, therefore the the resistance of the regulator changes as the system voltage changes, always trying to produce around 14 volts out. With the engine off and electrical power on, the regulator sees a low voltage and reduces its resistance to allow a higher current flow. As stated above, a higher current flow in the field produces a stronger magnetic field, which produces a higher output from the alternator. After the engine starts, the alternator will start putting out power. Once the voltage sensing limit of the regulator is reached (around 14 volts) the regulator sees this and starts reducing the current flow in the field coil. During operation this happens several times a second.

    So, depending on the operation of the alternator (engine off or on, low current load or high current load) the voltage measured at the field terminal will always be something less than bus voltage. AND each model of charging system will measure slightly different. For the InterAv system voltage checks, start at the alternator output terminal. This should read bus voltage of around 12 volts with engine off. Then check voltage at the regulator terminal on the back of the alternator. This should be 1 volt according to the troubleshooting chart. 1 volt because the power for this circuit is supplied through a dropping resistor shown between the reg and output terminals. The regulator + terminal should also read 1 volt because it is the other end of the wire connected to the alternator reg terminal. The chart calls for 1 volt at the regulator field terminal. Same reading at the alternator field terminal as it is the other end of the reg field wire and wires/relays/switches have no meaningful resistance.

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  36. #36

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    Another video for others that run into any abnormalities on their Interav charging systems. This video shows the DC voltage readings when multimeter + connected to the Reg Terminal on the Alternator and multimeter - connected to the grounding source of the Alternator and Regulator (these two are terminated at the same GND).
    First measurement= .002 VDC: Master relay OFF, Alternator/Field OFF.
    Second measurement = 6.91 VDC: Master relay ON, Alternator/Field OFF.
    Third measurement= .94 VDC: Master Relay ON, Alternator/Field ON.
    Fourth Measurement = 15.32 VDC: Master Relay ON, Alternator/Field ON, Engine Running.
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  37. #37

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    Well, my previous “solution” has failed or the hardware has finally thrown in the towel. Was out on a flight when I observed a significant noise increase on my radio reducing my reception to next to nothing and in and out. Shortly thereafter, back to no positive deflection on my ammeter. Wondering if this is worth chasing via troubleshooting or time to move on. If moving on, Wireweinie has indicated that Plane Power is the way to go but when I research that solution it seems I must also relocate my oil cooler to the rear baffling (read:extra work and extra $$). I also see B&C 400 systems would work and even tout not having to relocate anything. Anybody care to weigh in on this?

  38. #38
    wireweinie's Avatar
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    Plane-Power will work but you'll need to bend the oil cooler leg.

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  39. #39

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    Wireweinie this “leg”?
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  40. #40
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    Nope. That is some cobbed together piece for an inter-av alternator bracket. The best way will be to fab a new bracket leg or mod an original one to fit, with the alternator mounted.

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