charging problem

[eski]

My alternator keeps falling off line. It does not matter what the load is. I can bring the alternator back on line by turning offf the master switch for a few seconds. It is a three position switch. Centered it is off, up or down it is on. In flight with the switch off, all components are powered and the voltage is aprox 14.9 volts. In either on position the voltage is 13.9 volts. It stays on line for 10 to 30 minutes. Lately it stays on line shorter. The overvoltage relay has been replaced and I am still troubleshooting. Any suggestions

 

[Steve Pierce]

Glass fuses and old fuse holder? Seen problems with them. Which alternator are you running. I have seen the regulators get hot and break down, switch off for 30 minutes and it works fine. The owner kept having this problem. Alternators usually just quit. Regulators break down and quit intermittently.

 

[BradleyG]

I had the same problem in my Cub. I ended up changing the entire system. Alternator, Regulator, Over Voltage Relay, and Capacitor. All parts were from Inter Av. I ran the Inter Av trouble shooting chart and it was not definitive on what was bad.

After sending all parts back to Inter Av, they could only verify, that of all the parts, the regulator was the only definite bad part. They tested all parts in their shop. Since the entire electrical system was original (30 years old), and had no documented service or replacement, I elected to replace the entire system. No problems since.

 

[mike mcs repair]

My alternator keeps falling off line. It does not matter what the load is. I can bring the alternator back on line by turning offf the master switch for a few seconds. It is a three position switch. Centered it is off, up or down it is on. In flight with the switch off, all components are powered and the voltage is aprox 14.9 volts. In either on position the voltage is 13.9 volts. It stays on line for 10 to 30 minutes. Lately it stays on line shorter. The overvoltage relay has been replaced and I am still troubleshooting. Any suggestions

alt brand(s)??? (alcor/interav/piper, B&C, Plane Power?, ford/cessna?)

amp meter (analog) steady or needle bouncing? (bouncing = bad shorted diode(s))
if its like an interav clean where the regulator red wires hook to and also where the over voltage red wire hooks to, since they may be seeing different voltages..

if its a ford/pestolite style you may have an bad spot on field wire, intermetently grounding of the field wire inside the shield turning alt on(but you would hear allot of static as this happens)

add at temporary ground wire say a #8 from engine case to one of the small #8 studs ON fuselage coming through firewall .... the original grounding method is useless...

also you can hook up a volt meter so you can watch it in flight, and see when it quits, it sounds like the voltage is going high and overvolt is doing its job and tripping....

also do you have access to another battery you can try, sometimes a flaky Cell or a loose plate in it will drive you nuts.... (one cell intermittently dies, regulator sees that volt drop and pours the coal to it and goes too high, hence tripping the over voltage relay)

also keep all expensive stuff (radios & such) off/ breakers pulled till you get this fixed...

 

[eski]

All components are inter av and the needle is steady. I have replaced the voltage regulator with no change in results. I do have the glass fuse holders and have been thinking about replacing them. Any Ideas or schematics on how to wire the new system.

I have replaced the battery and since doing so the alternator stays on for a shorter period of time. The other new occurence is that with the master switch in the off position, the radios and all lights stay powered. I am thinking that the switch is the problem.

 

[Steve Pierce]

I would use this and start troubleshooting. http://www.inter-av.com/Alternator.htm I have seen the old fuse holders corroded or just not making good contact.

 

[mike mcs repair]

you are not supposed to use the 30 amp fuses & block with the 50/60 amp alternator installation.... they should have change it to a master solenoid setup when they installed alternator... someone goofed...

that sounds weird and scary about the stuff staying turned on.... switch full of water? that also would energize the alt field too much (field is on other half of master switch, one side fuses, other side field.. (if not using separate field switch))

or do you mean with it running if you turned of master, radios and stuff stayed on? (that's normal, but severely frowned upon turning off master with alt running)

 

[Fabman]

Try one of these. This diode has cured charging problems for me a number of times.

http://www.aircraftspruce.com/catalog/elpages/solenoidassy.php

 

[mike mcs repair]

Try one of these. This diode has cured charging problems for me a number of times.

http://www.aircraftspruce.com/catalog/elpages/solenoidassy.php

totally different issue here... that solves the spark jumping back across start switch contacts as start switch is released, from back EMF and corroding the contacts inside starter switch/key switch, hence not pulling in the start solenoid fully when trying to start......... not at all related to this issue....

 

[Steve Pierce]

Mike, I was thinking the late model Super Cubs that I have worked on with the Interav alternator installed at the factory had the fuses. I'll have to look.

 

[Fabman]

Mike,
I do realize that if his charging system is working properly for 10 - 30 minutes and then falling off this it probably not going to cure it, but I still would not hesitate to install if there is not one. Also if someone in the future searches this site for "charging problems" this common solenoid problem may cure their problem.

 

[mike mcs repair]

Mike,.....if someone in the future searches this site for "charging problems" this common solenoid problem may cure their problem.

not to be picky...but... I don't get what you are driving at....yet

that has nothing to do with the charging system that's usually just on starter solenoid,

or am I misreading your message and you are meaning adding a diode on master solenoid to save master switch contacts????? now I'm curious..???

 

[moneyburner]

Check the 75 Ohm resister on the back. It may be failing intermittently in use. You have to pull it off to check it, of course.
p/n: 655-64139.

Another thing that will cause trouble is the brushes and brush holder. A poor connection or sticking brush will shut you down, or degrade output.
p/n: 115-09964.

Check ALL your grounds, and make sure you aren't depending upon structure for a ground path; you have to use wires and they have to have pristine connections with no opportunity for oxidization. Same goes for the conductors and regulation.

Or, of course, it could be none of the above. I have found all of the above things causing similar mischief.

 

[mike mcs repair]

Mike, I was thinking the late model Super Cubs that I have worked on with the Interav alternator installed at the factory had the fuses. I'll have to look.

they have a master soleniod and the small on off master switch

 

[Steve Pierce]

Your right Mike. Too many Cubs and too few brain cells. :lol:

 

[eski]

Thank you for all the opinions and advice. This problem confuses and frustrates me. We have used the inter av trouble shooting chart. To clarify, with the engine running, if you turn off the master the power is still supplied. ( I know bad ) If you turn off the Alt field switch, the system is totally depowered. I am not a cub expert and assumed that the master switch would kill all power as in most airplanes. I also assumed that the Alt switch was to isolate the alternator for an overcharging event. Thank you Mike for explaing how this works.

We tested the master relay. It is a 6 volt relay. Is this normal in a 12 volt system? It would open at 2 volts and draw 6 amps. That seems like a lot of amps. In comparison a 24 volt relay only drew .8 amps. Question Should this be a 12 volt master relay?

The alternator does have its own 60 amp breaker. Does any one know where I can find a wiring schematic? I am confused about how to eliminate the glass fuses and the holders.

We are thinking about replacing the the overvoltage relay. If that doesn't work we will look at the alternator a little closer.

 

[Louis]

In flight with the switch off, all components are powered and the voltage is aprox 14.9 volts.

i did have the same problem. Then, when it reach 15 volts, the overvoltage cut-off box will cut the charge.

Did you solved your problem ? I did and ready to help.

Louis

 

[mike mcs repair]

.....We tested the master relay. It is a 6 volt relay. ....Should this be a 12 volt master relay?

that sounds like the starter solenoid(since you say you have fuses back there still), and 6 volt is right for starter solenoid because its only on for a few seconds, they did this to eliminate the solinoid dropping out/chatering as battery got lower with cranking with old weak starters... not so much of an issue with the new starters.... I have used 12 v ones with no problems....

Does any one know where I can find a wiring schematic? I am confused about how to eliminate the glass fuses and the holders.

the solinoid will go exactly where the fuses are, .... but you must change some stuff in wing root end of wires/switch also... cant explain right now..

We are thinking about replacing the the overvoltage relay. If that doesn't work we will look at the alternator a little closer.

you can check with a voltmeter watch buss voltage to see when it trips, it should not trip below 15.5 volts i think....

 

[supercub24a]

sounds like the regulator sence wire is not sencing the proper voltage and tripping the overvolt rely if the regulator sences lower voltage (resitance in the wire) on the inter Av system the it sences alternator voltage off the alternator the wire from the regulator to the alternator either marked Aux term ?? or Reg term its the one hooked to the small term with the diode
good luck !

 

[mike mcs repair]

.....Reg term its the one hooked to the small term with the diode
good luck !

yes reg terminal,

I always figured it was a diode too... but it is actually a resistor that gives a small trickle to get regulator started charging.....

On an INTERAV/Motarola ONLY
if this resistor breaks, symptoms will be this:
no alternator output, BUT if you briefly put some voltage to the field wire with engine running the alternator will start and run fine.... until engine stops.. then it will not charge again unless you put voltage to field.. rinse -repeat...

replace resistor to fix..

but don't bother replacing resistor unless this happens...

.

 

[Louis]

To clarify, with the engine running, if you turn off the master the power is still supplied. ( I know bad ) If you turn off the Alt field switch, the system is totally depowered. I am not a cub expert and assumed that the master switch would kill all power as in most airplanes. (

Wich airplane ? No Cessna for sure, neither Piper, or any i tried that did not a have a split switch.

The alternator is perfectly capable of powering the bus without the battery online (master OFF).

That's why Cessna use a split switch since 40 years, wich , mechanicly, won't allow the alternator field to be ON when the master is OFF. But if the arrangemnet allow you to put the field alternator ON, and the master OFF, you will have electricity on the bus.

Louis

 

[mike mcs repair]

.....
That's why Cessna use a split switch since 40 years, wich , mechanicly, won't allow the alternator field to be ON when the master is OFF........
Louis

and that's exactly why I too use that switch in every new panel or rebuild....

 

[Fortysix12]

Consider that the overvoltage relay is doing it's job correctly. Here's a good read. .
http://ronkilber.tripod.com/alternat/alternat.htm

 

[mike mcs repair]

Consider that the overvoltage relay is doing it's job correctly. Here's a good read. .
http://ronkilber.tripod.com/alternat/alternat.htm

looks like a great read... only skimmed it, will do a good read later

 

[Gordon Misch]

Fellows, please help me in my ignorance here - Why is it bad to energize the alternator with the battery (master relay) disconnected? I was thinking to use separate master and field switches, but maybe I should reconsider? Thanks - -

 

[Gordon Misch]

bump

I don't have a clue on my question - sure would like some enlightenment - -

 

[mike mcs repair]

bump

I don't have a clue on my question - sure would like some enlightenment - -

I still have bruises from the last time this came up on the sister site so I was just gonna keep my head low....

I stated whats right.. to me, but others have different views....

http://www.shortwingpipers.org/foru...rsion-kits&highlight=master+switch+alternator

 

[Gordon Misch]

Thanks, Mike. So, having read the thread you referenced, it seems you're thinking the regulator can't respond fast enough to changing loads, without the damping of the battery. Do I have that right?

 

[fobjob]

Bear in mind that those fuses can go intermittent internally ...