Bench testing a starter

Zachary Hoyt · Oct 2, 2010

I know this is a dumb question, but I still feel a need to ask. What is a proper way to bench test a starter to see if it runs? I have a 12v battery booster pack, the kind you keep in your car(or don't, in my case). Would it be reasonably safe and electrically appropriate to put the starter case in a post vise, hook the red wire to the post on the case, hook the black wire to the vise handle and flip the switch? Would I be better off just to put the starter on the floor and connect both wires directly to it? Are these both bad ideas? It is a Case VAC starter, if that matters. Thank you very much for any advice.
Zach

Allan in NE · Oct 2, 2010

I just throw the darned things on the floor and spin 'em up.

It kind of takes a little "experience" to tell if they are coming up to proper speed or not. After you've done a few of 'em, you can just "hear" it.

Still and all, to really check out those field windings, the old gal needs to be under load and HOT.

If the starter drags when hot, but seems plumb okay when the unit is cold, you can just bet it has shorted field windings.

Allan

dpurvis1 · Oct 2, 2010

do it in the vice but just touch ground to starter ear. will work on floor but not as handy.

Goose · Oct 2, 2010

I usually just hook jumper cables to a battery, hook the positive cable to the positive lug on the starter, and tap the starter case with the negative cable.

Holding the starter solidly by hand to any solid surface should be enough to keep the starter from flying around from the torque.

The starter shouldn't sound like it's struggling. Within a second or two it should hit a certain rpm and maintain that rpm. The Bendix drive should kick out into the nose. Like someone else said, you develop an ear for it.

C.R. · Oct 2, 2010

most GOOD shops will throw it on a tester for you no charge

old · Oct 2, 2010

You can do it in a vice or one the floor or just about any place but be careful if it spins up it can/will jump and twist and turn on you and if you have body parts in the wrong place they will no long be there. That said any good auto parts store will test one for you for free and they can do tests that you have no way of doing like load test and amp draw which are important ya you can see if it spins but that is about all you can do and yes I do it all the time but I also have time on my hands and play with lots of these old machines

JDemaris · Oct 2, 2010

For bench testing, starters are rated by amp draw at free-spin testing, RPMs, and amp draw with armature locked.

It's not something I usually do. If you're used to fooling with them, you can pretty much tell just by how they sound when you hook a battery to them.

VAC usually has an Autolite MZ-4114 6 volt-system starter, made to work properly at 4.5 to 5 volts.

Test as thus:
No load - hooked to a good 6 volt batttery - voltage at starter should read 5 volts, RPMs should be 4000, and amperage draw is 68 amperes.

If you lock the starter so it cannot turn, voltage should drop to 2 volts, and amperage draw should jump to 280 amperes. Torque at that time being made is 4.4 foot pounds at the starter-drive.

gene bender · Oct 2, 2010

Clamp in vice tite and use a 6v batt

RodinNS · Oct 2, 2010

I just stick the booster cables on them with the starter on the ground and one foot on the motor so it doesn't flip over.
Keep in mind... if this is a bendix drive type starter without a solenoid you're probably going to unwind the bendix... so that's not recomended.

Rod

barn E · Oct 3, 2010

If you know what you're doing, just put it on the car. Waste of time unless customer insists. Used to know what I was doing.

Bench testing a starter

Zachary Hoyt

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Allan in NE

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dpurvis1

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Goose

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C.R.

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old

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JDemaris

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gene bender

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RodinNS

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barn E

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