Testing starter solenoid

How do you test a 12 volt 4 terminal insulated starter solenoid. It is on a lindsey air compressor with 360 Dodge engine.
Thanks

Hello Steve-Maine,

How many terminals, besides the starter and battery side?

Guido.

If it is mounted on the starter and moves the starter drive into engagement, there are probably 2 big posts and 2 little posts. One big post will be attached to the starter input conductor, and the other to the battery hot. one small terminal would be labeled S for start, the other I for Ignition. you can ignore the one to ignition for testing. Put a ground on the body (if not connected to the starter) and connect the Battery input terminal to the hot jumper from the battery. Then jump from the battery hot terminal to the S little terminal. I cannot see what you are looking at, but that is the best I have. Jim

One of the small terminals needs to see 12 volts when key is turned to start and the other small terminal needs to be grounded to the mounting screw of the solenoid or frame ground. The two large do what Janicholson said, but ignore what he said about the two small terminals since he didn't read that it was an insulated solenoid. The insulated solenoids I've seen the terminals aren't labeled like he said.

2 small terminals

Hello Steve-Maine,

One is either a ground or is grounded by a safety switch. The other is the ignition switch power. You need to find the ground. Once you do, put power on the other small terminal.

This will engage the solenoid to transfer power on the starter side. If the starter does not engage, assuming it is good, and all connections are also good, then the solenoid is bad. MAKE SURE THE SOLENOID IS GROUDED.

You can hook up a volt meter on the starter side to see if you are getting any power also. See how you make out. Let me know if you need more help,

Guido..

The small terminals require 12volts across them, however you decide to accomplish that. Result will energize the solenoid and you can hear it click. The large terminals then should read zero ohms across them.....don't forget to calibrate your 0 ohms function by shorting your leads together first and adjust the needle for zero on an analog, or take note of the lead resistance if digital....my HF cheapie runs 0.4 ohms lead resistance.

You're not done yet. Next thing is the condition of the contacts. If pitted, they won't carry the 200-300 amps required for engine starting. What you do to determine that is to get a helper. Then have the helper attempt to start the engine while you measure the voltage across the ⅜" studded high current terminals. If you read anything but millivolts, you need to get another, or disassemble the one you have and flip the contacts around, burnishing as required, to get solid copper on solid copper.

What are you wanting to test?

Does it not do anything? No clunk?

Isolated ground solenoids are rare, but they do exist.

The difference is the internal wiring. The 2 small terminals are connected to the coil that closes the contacts.

Putting 12v across the 2 small terminals will close the contacts.

Typically this type solenoid will incorporate some type of safety device to complete the ground, so be careful grounding one side if it is not factory wired that way.

A non isolated solenoid, most common type, uses the mount bracket and the "S" terminal to energize the coil. The "R" terminal is not used, or is used a a resistor bypass on a spark ignition engine.

To tell the difference, put an ohm meter across the small terminals. If you get a reading, it is an isolated ground. Checking from the "S" terminal to the mount bracket, it will be a non isolated ground.

Does it "clunk" but no start?

Check the voltage on the battery side large terminal. Should be battery voltage to ground all the time.

Energize the solenoid. Should get battery voltage to both large terminals.

If the battery side stays at 12v, and the starter side stays at zero, or very low, the solenoid is bad.

If both sides drop to zero, or very low, there is a bad battery connection, low/bad battery. If the cables jump and get hot, there is a short in the starter or the engine is locked up.

If both sides stay at 12v, and no start, there is a bad connection from the solenoid to the starter, the starter is bad (open), or the starter case is not grounded.