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charging system schematic

docdray

docdray

Oompa Loompa
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Location
Cleburne, Texas
first, I apologize if I missed it-but I cannot find a diagram for the charging system on a 94-95. the username/password in technical library link does not work for me, search came up nada many times. so can anyone send me this please, or let me know where to find it?

problem is alternator starts cold at 14.3 volts on new batteries, as engine warms it drops to 12.7:confused: with no unusual load, tried 2 new alternators and same. problem started 9 months ago out of blue- and yes, cleaned and even ran new grounds. p terminal runs 5.2 volts- a little low and L is 11.6 :wtf:- something isn't right, but I hate to tear wiring apart to trace the wires out- any helps appreciated.

BTW: voltage measured on voltmeter and gmtdscan.
 
Is it a slow drop in voltage, or just drops off suddenly?

The regulator is inside the alternator. As the alternator gets hotter, the voltage tends to go lower in mine. Cold winter morning 15+ volts/Hot summer day 14 or just under if you are lucky on the dash.

Got an DC amprobe/amp clamp to measure what's happening?

If you had a wiring issue, I would think it would be either open or short... work or not... or fuses be blowing, but I don't think that's your issue.

Does the voltage come up if you pop the hood and keep underhood temp down?

New alterntor, OEM, reman???
 
If you still need it when I get home tonight I have the 95 factory manual. I can scan it(if I can find it those manuals are poorly laid out). Not unusal at all to have to bad alts in a row BTW. My 2000 the problem turned out to be the batt wire on the back of the alt. It looked fine but was hanging on by a thread of wire and causing resistance.
 
I could only suspect you have a short to ground somewhere that is pulling a lot of amps off and the alternator cant keep up.

Otherwise my car will do the same thing after I put a smaller crank pulley on it ("underdrive"). If you put a larger alternator pulley on it might cause that too. Is it just that crummy tiny 100 amp alternator? It probably sucks at idle if you have any load on it. And besides that like 10 gauge wire that runs from the alternator to the battery is insufficient.

Does it coincide when the truck goes from high idle or timing to lower idle/timing as it warms up?
 
gauge size is #4, no difference on rpm. problem started during the middle of a haul. so I do not believe pulley size is a factor. The alternator is an autozone 105a gold. I forgot this is the 3rd alternator as 2 months ago the bearing in the duracrap one went out in houston.

since it is 71f here today its ok at the moment but heat might play a part

out of curiosity, does anyone have the L pin voltage on a fully warm engine?
 
I think you're gonna need a DC amp clamp to check to see if you have a load, or a generation issue.

Too many things checkout... unless did I see that you said "Autozone Gold" like their in house reman brand? Maybe a bad run of those alternators... but that many in a row is toooooo odd.

I picked a meter up cheap off of that famous auction site. Great for diagnostics on charging system problems. It showed me that the generation was equal to less than what the load totalled up to.
 
currently running 38 amps @ 14.42v for 22 min. all of a sudden it wont drop voltage tonight- go figure. have don a lot of reading here and other site, double and triple going over issues. raining this weekend, dig into hopefully mon or tuesday.

first one was orielly then 2 from the ozone
 
Generating or consuming 38A? Generating read off of the alt lead itself. 38A steady from start up for a straight 22 minutes?

Anything blowing a lot of heat toward that alternator like some sort of exhaust leak like a blow torch on the alternator? Just grasping at wild crazy ideas....
 
was running lights, fan etc for load--anyway today was warm enough for problem to kick in. thought about IP diagnoses and when I poured cold water on alt, I watched volage rise surprisingly fast-from 12.9 up to 14.45v. engine at 185 outside was 88f. any one else experience this???
 
Does the pulley spin freely with no belt?

As metal heats it becomes higher resistance with higher voltage drop, so something must be getting too hot, and youve tried multiple alternators. I can't think of what it could be, other than the lug and cable to the battery if its not making good connection.

Maybe do an ohm check on the cable when its warm.
 
Alternator capacity get's compromised when you turn up the head.

Check out Penn-Tex's website to give you an idea about what happens.

I hope this isn't a case of where the autoparts store is giving you the wrong alternator for the application.
 
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