Defective solenoid?

[Helmetfire]

Is this solenoid (starter) busted?? It's brand new from spruce, I hooked it all up to check it and found that it wasn't working as I thought it should. You can see in the pic that there is continuity between the RHS coil terminal and the case mount...is this right?? There is no continuity between the two coil terminals. The coil terminals should show continuity and be reversible, correct?

I originally had a ground jumper hooked to one coil terminal (marked "I" on the case), from the master relay, which is the same ground source that activates the master solenoid (from master switch). The other coil terminal was hot, simulating power from start switch. The solenoid wasn't activating in that configuration so I looked a little closer. I found that the solenoid would only activate with a positive wire on the right coil terminal (marked "S" on the case), and the case mount grounded. The weird part was, the left coil terminal would show 12V while activated.

no instructions came with the solenoid. The only markings were "I" and "S" on the coil terminals, and "12V" stamped on the lower right portion of the case mount.

this pic shows my original mounting setup that wasn't working.

 

[qsmx440]

If you reverse the wires (black and red) as shown in your first photo does the continuity go away?

 

[Helmetfire]

Nope

 

[btracy]

This should be normal. It appears to be a Ford type automotive solenoid. The " S" is for start. When Power is applied to this terminal the coil is energized which closed the contacts to send power to the starter. The coil is grounded thru the case and what you are seeing is that the coil is good. The "I" terminal is for ignition. When you turn the key there is no voltage to the ignition system momentarily while the starter is engaged. The voltage to the ignition system while the starter is engaged is thru this terminal. Want to hot wire an old ford. A jumper wire from the large battery+ lug to the "I" terminal. your cee tee pliers across the Large + lug to the "S" terminal and you are going faster than you can find the keys in your pocket.

 

[Aviator]

Like btracy said, sounds like you have an automotive solenoid.

Here's a brief rundown on how it works...

You should have the following voltages coming from these terminals with the key in the "on" position. Zero volts at "S" and about 8 volts at "I". The starter solenoid "S" terminal is nothing more than the positive side of a wire wound electro magnet. The negative side of the winding is internally attached to the mounting bracket of the starter solenoid and becomes a ground when the bracket makes contact with chassis ground by the bracket's contact with the inner fender when it's bolted down, completing the circuit.

When terminal "S" gets energized, (12 volts, key in "start" position), it creates a magnetic field that draws the contacts of the large terminals together and the "I" terminal also gets energized and delivers a full 12 volts at the same time. You will only have the 12 volts there when the solenoid is energized and voltage to the starter side, (large terminal), is present.

Again, the only time there should be voltage at the "S" terminal is when the key is in the "start" position. The "I" terminal wire will have 12 volts at the same time. This wire is connected to the ignition coil circuit and provides a full 12 volts to the coil to make it easier to start the engine. It by-passes the coil's ballast resistor wire, which when in the "on" position, delivers a lower 8 volts to the coil (the voltage is now routed through the ballast resistor) to prevent the coil from overheating and to help the ignition points to live longer.

If you were to disconnect the wire to the "S" terminal with key in the "on" position and take a voltage reading at the wire itself, it should show zero volts. At the "I" terminal, again disconnected and checked the same way, there should be approximately 8 volts present. (the voltage is backfed through the wire from the coil)

The 8 volts at "I" will have no effect on the solenoid itself in the "on" position because it is now an open circuit, at this point, unless the solenoid is energized and the key is in the "start" position.

 

[cruiser]

I have a solenoid that reads infinity, max resistance, from either of the control circuit studs to the case. It is a continuous duty solenoid, not a starter. To operate it requires a positive on one stud and ground on the other, grounding thru the case results in no operation of the solenoid. Perhaps this link will help. Jim http://www.colehersee.com/home/special_solenoid_applications/

 

[Darrel Starr]

I would upload the part of my wiring diagram that is in the Members area, Tech Section. But I can't upload anything this evening to this web site. I do have though in the Members area a diagram that shows how to wire these solenoids. Sorry I can't help more, don't know if the problem is my computer or in the web site?????

 

[cubunltd]

For one thing your master solenoid is not right. you should only have one small terminal on it and there should not be a wire running from it to the starter solenoid. They are two different circuits!

john

 

[mike mcs repair]

and also...
the + cable should be hooked where you have the big white with orange boots wire... you do NOT want to run the starter sol off the master.. (that just eventually adds 2 more sets of bad contacts/loss in the start circuit with NO benefit)

so usually you have the big batt + got to the starter sol in, JUST LIKE PIPER DID originally on all them... with a jumper of buss wire size feeding master, from output of master you just go to amp meter(or have a CB like you show in that line)

 

[Helmetfire]

http://www.supercub.org/photopost/data/500/PA18_elect_schem.jpeg

and also...
the + cable should be hooked where you have the big white with orange boots wire... you do NOT want to run the starter sol off the master.. (that just eventually adds 2 more sets of bad contacts/loss in the start circuit with NO benefit)

so usually you have the big batt + got to the starter sol in, JUST LIKE PIPER DID originally on all them... with a jumper of buss wire size feeding master, from output of master you just go to amp meter(or have a CB like you show in that line)

Every piper diagram I have seen shows the start solenoid powered by the master solenoid, and that's the way this plane was wired before I started this project. I see your point, and it makes sense, just trying to stay as close to late model wiring as possible.

For one thing your master solenoid is not right. you should only have one small terminal on it and there should not be a wire running from it to the starter solenoid. They are two different circuits!

john

If the above link works, i believe the wiring diagram shows the master solenoid has two coil connections and the start solenoid is a case ground....

as far as the ground wire, I figured since the start solenoid wouldn't be usable until the master is activated by the ground wire, that I could use the same circuit for the start solenoid ground...I could run the ground from another source, but figured this was good as any??? Anyway, it now needs to go to the start solenoid case, instead of the coil terminal.

I would upload the part of my wiring diagram that is in the Members area, Tech Section. But I can't upload anything this evening to this web site. I do have though in the Members area a diagram that shows how to wire these solenoids. Sorry I can't help more, don't know if the problem is my computer or in the web site?????

I have your wiring diagram taped to the wall in my office :lol: I should have consulted it before I wired this up as I noticed on one of your posts you have the same solenoid.

 

[Darrel Starr]

Thanks, that was nice.

 

[mike mcs repair]

..
Every piper diagram I have seen shows the start solenoid powered by the master solenoid, and that's the way this plane was wired before I started this project. I see your point, and it makes sense, just trying to stay as close to late model wiring as possible.
....

somewhere along the line when the redid them for the move to florida, they wired them like tanks with tons of extra useless ground wires and such.... stick to the old original wiring (fuses).....

 

[Helmetfire]

somewhere along the line when the redid them for the move to florida, they wired them like tanks with tons of extra useless ground wires and such.... stick to the old original wiring (fuses).....

Right?!?! I really don't think a master solenoid is even necessary given the low amperage requirements of my particular application, especially since I have the C/B accessible underseat...just trying to keep the FAA happy I guess...

 

[mike mcs repair]

Right?!?! I really don't think a master solenoid is even necessary given the low amperage requirements of my particular application, especially since I have the C/B accessible underseat...just trying to keep the FAA happy I guess...

true, with the proper large master switch as the originals had... (depending on charging system size, thats what made most of them need the master solenoid, the charging system was larger than the switch and fuses were rated for...)

 

[skywagon8a]

That looks like the starter solenoid which I got from Spruce. A+ from the starter button is connected to one of the small terminals. The other small terminal has a jumper to ground (one of the solenoid mounting bolts). Not sure if it matters which small terminal does what? Check it with some jumpers on a battery.

I used a master solenoid in series with the starter solenoid on my Cub, contrary to what is said above, because that is the way that Cessna did it on my 185 which has worked very well for the past 38 years. The original master solenoid is still working just fine.

 

[Darrel Starr]

Well I finally got the document to load from my wife's computer but can't seem to do it from mine -- must have something blocking uploads. Thanks for your help SJ. This is just a 38 kb file.

 

[Darrel Starr]

Success -- I switched to Google Chrome from Internet Explorer 9, 64 bit and now I can upload pictures again. Don't know why Internet Explorer no longer works but I did update from 8 to 9 so maybe that is it. Vivian is still running IE 8 so maybe that is why I was able to upload a picture from her computer ... not sure.

 

[coxcub]

Starter Solenoid Query.

Folks - being an electrical numb skull perhaps One of the many Gurus out there can confirm I have the correct part.

My 1956 PA18 150 starter solenoid sticks in the off position and needs 'firm tap' to get it on line - It has the single connection to the coil (ground through the case).

I have just received Part No.U487-149 from Univair as an alternate to Piper Part No.487-149 and note that it is for 6 volt operation - Is this correct due to voltage drop when the starter engages or should it be for 12 volt operation? - it also has 2 coil connections.

Many thanks

Frank

 

[wireweinie]

CoxCub
This is the correct solenoid. The original Piper installation used a 6 volt starter solenoid. Intermittent duty keeps it from overheating and the harsh mechanical action of the solenoid helps keep the slag from building up on the internal contacts. As for the two coil connections, connect one to ground and the opposite to the starter control wire coming off the key switch (or starter button). It doesn't matter which terminal is ground and which is hot