What have you done to your square lately??

[JamesSam]

I also did an old school trick similar to what @Ricko1966 and @Grit dog were stressing, but instead of unplugging the alternator I fired it up and took the positive cable off the battery while running. The truck kept running.

So does this mean the alternator is good? Or that I should probably still check with the incandescent bulb for possible bad diode?

 

[Ricko1966]

I also did an old school trick similar to what @Ricko1966 and @Grit dog were stressing, but instead of unplugging the alternator I fired it up and took the positive cable off the battery while running. The truck kept running.

So does this mean the alternator is good? Or that I should probably still check with the incandescent bulb for possible bad diode?

No that doesn't mean the alternator is good..

 

[Ricko1966]

I bought a battery/alternator test probe, and test probe light from Advance. I did test with the battery/alternator tester. Battery:

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Alternator:

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Still not an adequate test. That does not test the diodes.

 

[JamesSam]

So I got a digital multimeter and headed out to the truck to test AC current on the alternator and after my last trick test of removing the battery cable while running, the truck turns over, fires up and cuts out immediately. What did I do?

 

[JamesSam]

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[Ricko1966]

So I got a digital multimeter and headed out to the truck to test AC current on the alternator and after my last trick test of removing the battery cable while running, the truck turns over, fires up and cuts out immediately. What did I do?

Possibly smoked the ICM or ECM. Not definitely but that would be my first suspicions. And the ICM is different on a TBI car so they can fail where they start but don't run,unlike earlier where they were just they spark or they don't. Check both ECM fuses first.

 

[JamesSam]

Damn, did I just fry the computer?

 

[JamesSam]

It will not stay ignited. I cannot think of what to do next.

 

[JamesSam]

Quick research turns up that removing the positive cable may have reset the ECM, or worse, or maybe not at all. I saw multiple explanations saying both and/or maybe...
Did I just kill all the electronics in my truck?

 

[JamesSam]

It occurred to me to disconnect the negative cable for 5 minutes. I reconnected it and the truck cranked up and stayed on.

 

[JamesSam]

Tomorrow when the sun comes up, I will go back with the multimeter and test AC on alternator.

 

[Ricko1966]

Tomorrow when the sun comes up, I will go back with the multimeter and test AC on alternator.

An you still need to check for a draw on the battery.

 

[JamesSam]

An you still need to check for a draw on the battery.

That too.

 

[Radiohead]

So I got a digital multimeter and headed out to the truck to test AC current on the alternator and after my last trick test of removing the battery cable while running, the truck turns over, fires up and cuts out immediately. What did I do?

Yeah, don't ever do that again. This isn’t 1967.

 

[JamesSam]

Yeah, don't ever do that again. This isn’t 1967.

Never again.