1996 Gmc 2.2 Alternator Circuit Drawing
1996 Gmc 2.2 Alternator Circuit Drawing
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Discussion Starter · #1 ·
Battery light came on and dash volt meter began dropping. I had just replaced the battery so I assumed it was the alternator (dumb to assume).
Replaced the altrnator. Problem still exists. When engine running volts slowly drop till engine dies.
Diagnosis done so far:
New alternator installed
Battery load test: good
Battery fully charged
Battery connections clean and tight
All grounds clean and tight
All fuses checked and good
Parasitic load test good
Serpentine belt telt and clean no noise, no cracks, no shiny spots
Multimeter Info:
Large lug on back of alt reads equal to battery volts when meter grounded to battery or alt case with engine running. If the battery has 11 volts left, thats what I get on the back of the alternator. If the battery has 9 thats what I get.
It seems that the alternator is putting out no power. Every part of the system matches whatever volts the battery has left.
Tried a different battery (in case cells were bad and did not show on load test) results were the same.
I dont think there are any shorts in the system since the volts at the back of the alternator match the volts on the battery. This tells me there is no loss anywhere in the system. Also, hooked a set of jumpers to my other truck. Other truck ahd 14.4 volts at battery with engine running. Checked the back of my alternator while the jumpers were connected and it read 14.4. Bad wire or ground pretty much ruled out.
I did connect multimeter to the connecter going into the alternator (single red wire into four pin connector). I am only getting 4.94 volts on this wire that goes into the alternator. I checked in front of and behind the connector to ensure the connector is good. 4.94 volts on both sides.
Questions:
Should this wire be supplying 12v to the alternator?
Also, does anyone know of any hidden fuses other than the dash panel and the underhood box?
Lastly, is ther any way to test the ECM short of installing a new one?
I am stumped and about out of diagnostic ideas. Any help would be great!
Thanks all!
Ryan
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6,049 Posts
all because the alt is new doesnt mean its good.bought a new one for a 03 eclipse and it was bad right out of the box.
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206 Posts
Might want to have it tested
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501 Posts
Yep, and also make double sure it is wired in correctly.
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Discussion Starter · #5 ·
Follow Up:
I pulled the new alternator back out and had it bench tested. The regulator failed. So I swapped for another new alternator. Had it bench tested before leaving the store. It passed. Put it in the truck and fired it up. Reading steady 14.4 volts. All looked good. Then all of a sudden the system dropped to 12 volts and slowly started falling.
I believe it is burning up voltage regulators for some reason. Single small red wire to the back of the alternator is still only reading 4.94 volts steady.
Can anyone tell me what the voltage should be coming into the alternator. Does it vary from the ECM? Should it be steady 12 volts from the battery?
I am considering getting another new alternator and running a jumper straight from the battery to the connector on the back of the alternator to give it constant 12 volts. I am afraid of burning up another alternator. Pretty soon they are going to stop giving me warranty at the parts store and I cant afford to pay for another alternator.
So, if anyone can tell me what the input volts should be to the alternator, or supply me a wiring diagram I would be very appreciative.
Thanks
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127 Posts
If I remember correctly with the regulators our alts use, it has to be at least 10.1V for the alt to begin charging going into the voltage regulator. That's on the battery terminal on the back of the alt.
Attached a wiring diagram for reference, anytime you need one - Autozone.com and put in a 2002 S-10. The wiring hasn't changed much over the years, it'll get you where you need to go.
My best bet - that turnon lead from the ECM to the Alt is damaged or otherwise faulty connection wise. Whenever it's "unplugged" your battery light will come on, but more importantly the alt won't charge at all, as this lead turns the regulator and all the circuitry on. If it's loose and you keep getting load surges as it jiggles, you'll fry a VR if not your bridge very quickly, esp if your battery isn't fully charged.
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3,030 Posts
Where are you getting the alternators from? I'd have to suspect they're no good since you had good voltage at one point and then it suddenly quit.
Auto Zone remanufactured alternators are crap. My '00 had just gotten one on it the day before I got it, and it would sometimes do the same thing in the morning. Then the pulley came off it. Replacement from Advance Auto Parts hasn't missed a beat in 70k miles.
1996 Gmc 2.2 Alternator Circuit Drawing
Source: https://www.s10forum.com/threads/1999-sonoma-2-2-alternator-problem.506604/
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