More BS Alternator issues I cant figure out

Green96 said:
I kicked the issue to my eletrical engineer friend. I am at a loss. The only experience I have is with an Expedition with a Walmart battery job. They convinced the little old lady that it needed new harnesses too. they crammed 2 ground wires in a harness made for one. The problem being that most of the harness was painted. It was getting enough intermittent ground to start....sometimes. Back to the issue at hand.

I really have no idea what signals are being sent from the PCM to the alt. Are there multiple singals (I was thinking that there are at least 2), and did you test all of the wires between the alt and the PCM. It really sounds like you are only running on battery. 12.5-12.6 sounds right for a fully charged battery with no load. How long was the drive before it dropped down to 12V and stopped running?
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LOL I'm also an EE and think this is weird, especially when parts test fine out of the car and in another car. I wanted to check the PCM signal but my meter's Hz kept jumping around when I would probe the middle lead on the connector and the other to ground. Not sure if it was supposed to have a steady frequency or not..

I think I'm going to be buying an advance auto alternator to test and return if not needed.

Marty I too thought the clutch was internal.
 
ChiTownMaraud3r said:
Marty I too thought the clutch was internal.
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Many people assume there is an internal "clutch" because of the ability to turn the alternator off at WOT. This is done by shutting off the field current, not by mechanical means. The clutch in the pulley is a simple overrunning clutch which allows the alternator to free-wheel when the throttle is closed suddenly at high RPM.
 
Last edited:
Not to ask a dumb question, but the alternator in question (spinning backwards on an Eaton swap) does not have the stock clutched pulley which would just slip in reverse?
 
lifespeed said:
Not to ask a dumb question, but the alternator in question (spinning backwards on an Eaton swap) does not have the stock clutched pulley which would just slip in reverse?
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If I m understanding your question correctly, the answer is the stock clutch is removed in the Eaton swap process.
 
He fixed it.
Running a 4ga wire from the alternator case to the block resulted in 14.4 volts.

Which means the alternator bracket never grounded to the engine.
Of all things.....
I'm glad this case is closed
 
Zack said:
He fixed it.
Running a 4ga wire from the alternator case to the block resulted in 14.4 volts.

Which means the alternator bracket never grounded to the engine.
Of all things.....
I'm glad this case is closed
Click to expand...

My Mom said you can still come over to my house and play with me and the other kids!
 
An excellent example of the old days. Problem found, problem solved.

Iowa should get a little credit. He guessed a bad ground, not at the source, but still.
 
Wow. Who'd a thunk?


Self proclaimed Builder Of Badassery.

Buy it, Break it, Build it BETTER.
"Since 2004"
 
I tore my engine down today. I found the ground wire that splits off from the negative battery terminal and connects in front of the valve cover on the passenger side 1/2 way worn through the 6 ga. wire and it was green with corrosion. I was going to suggest this as a possible suspect. No issues with my car while this was happening.
 
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