How to bench test starter motor.
 

Gentlemen,

I just took the starter motor off my 2000 Expy and I want to bench test it to confirm that it needs replacing.

The ground (black) cable was connected to one of the starter motor body mounting bolts, so I can use the body as ground.

There are three connection posts on the solenoid:
- one with a little wire that goes directly into the starter, and that I haven't touched.
- a small post that had a smaller black wire in a braided jacket to it
- a larger post that had the red (positive) cable to it.

When it was on the vehicle, turning the key would cause the solenoid to actuate, but the starter motor didn't turn. Now that it's off the vehicle, I can't even get the solenoid to actuate. So I figure I'm just not applying 12v to the correct posts.

Anyone?

Thanks.

Never mind - figured it out.

With ground to chassis:
- 12v directly to the post with th little wire going into the body should drive the motor
- 12v to the small post should actuate the solenoid

On mine, both functions are hit and miss. That is, sometimes they work, sometimes they don't. Even with what I believe are good connections. Like it's stuck. Looks like I was lucky and it failed in the driveway instead of in a parking lot a hundred miles from home.

Sounds like one of those starter-mounted solenoid type starters. Many parts stores have setups where they can bench-test it for you, but it looks like you already figured it out. Starters have so much torque that I'm a little weary of setting it on the bench in the garage and trying to run it.

Torque - ya, I recall that from the last one I pulled years & years ago - but not this one. I mean, when it does turn, it jus turns. No jolting torque, just a gently turning motor. Maybe that's part og the problem.

i gently secure the starter in a vise to keep it in one place when i bench test one, had one get away from me a few to many times lol!

Since the gear is not engaged to anything but air, there is not much torque to worry about. Ive tested many starters on the garage floor. They just move a little bit. One important warning (no I did not do this myself), DO NOT TOUCH THE STARTER DIRECTLY TO THE BATTERY POSTS. Batteries give off hydrogen and oxygen when they are working and any spark can cause the battery to explode.

Jim

I used to bench test mine with vice and jumper cables, but now I just take it to the local Auto Zone and they test it.

I have had them wind up on the floor so now I use my big vice and a remote starter with my jump box to test them.

Its likely the solenoid on the starter itself that has failed. Permanent magnet starters are so incredibly more reliable than the old style starters they replaced. Usually the solenoid can be had for a fraction of the cost of a new starter, maybe $30-40 at most.