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Alternator or Voltage Regulator


Geeto67

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Having a little charging problem with the Jeep (1995 YJ 4.0L Manual). A couple weeks ago the battery gauge on the dash started jumping up from 14-15 volts to 9 and back again. Last week I went to start it and the gauge is holding at 10v. I took the battery out and put it on the charger and it charged right up to 12.8v. Put it back in the car and started it up and it started draining again. Put the multimeter on the output terminal of the alternator and ground it to the alternator body and saw 10 volts output (did I test that right?).

 

I am thinking that the voltage regulator has gone bad and is stuck at 10amps. Thing is I think the VR is part of the ECM. Is there a way to replace the Voltage regulator without having to replace the entire ECM? I have heard of people bypassing for an external voltage regulator, can I do that with the blown part of the ECM? or is it I have to replace and then switch to an external VR anyway.

 

Also did I test the alternator correctly? How can I tell if the alternator is bad without taking it out of the car and to a parts store? How do parts stores test them?

 

Finally, does upgrading to a 135Amp alternator make sense? the L6 in the GC uses a 135 peak amp alternator vs the 95amp used on the wrangler. It's a direct bolt in swap and the cost is about the same. I run two sets of aux lights - conventional cheapie 6" 55W halogen and a set of Cree LEDs. I was also thinking about wiring up a brighter reverse light.

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Take the regulator out and inspect it.

 

To do that I would have to open the ECM. Even though it's an unsealed OBDI unit from the 1990's I'm a little leery of how to test it.

 

Is the alternator making any noise?

 

none whatsoever

 

 

Most likely it's the regulator, rarely do alternators fail. Just replaced a regulator in my 300d. Same symptoms.

 

probably, though someone mentioned to me the diode. I think they were thinking of 1991 and earlier jeeps which have an external diode.

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