96 chevy tahoe 5.7 liter

buba943 · Oct 12, 2014

I have a 96 Chevy Tahoe I put in a new alternator and when it's idling it's running about 12 volts as so on as I put it into gear the volt gauge drops below 10 volts and doesn't have enough power to run the lights

lesterl · Oct 23, 2014

Moderator, please move to correct forum....

Have you tried a new Alternator? Was it NEW or REMAN, what brand?

buba943 · Oct 23, 2014

Yes I have checked it it's a new one and the brand is tough one or something like that new battery in it to

lesterl · Oct 23, 2014

Have you had the charging system checked?

lesterl · Oct 23, 2014

Where did you buy alternator at?

buba943 · Oct 23, 2014

Bought it at Advance Auto Parts what do you mean by charging system the alternator charges it

lesterl · Oct 23, 2014

Advance can put a small handheld device on the battery with car running and turn lights and such on and it can analyze the battery and alternator system...

buba943 · Oct 23, 2014

Yes I've had that done he said battery was bad got a new one same problem

lesterl · Oct 23, 2014

Cables tight? Ground straps good? Cable ends not corroded?

buba943 · Oct 24, 2014

Everything is tight and everything look good

lesterl · Oct 24, 2014

If you are brave/ careful I would take a Digital Multimeter and probe voltage at battery, Alternator stud (reference to engine block), and fuse block with engine running, also stop it and unhook the battery lead off the alternator and repeat testing.

Sounds like you got a DUD new alternator....

buba943 · Oct 24, 2014

I did that it said ut was pushing 18.7 volts

lesterl · Oct 24, 2014

Were all 6 tests showing 18V?

buba943 · Oct 24, 2014

No just the one off the battery and alternator

lesterl · Oct 24, 2014

Ok, so 18v at alternator and battery is BAD. You are cooking off the battery and possibly have damaged something else in the truck, I would stop using the car immediately and exchange the alternator out for a good one.

buba943 · Oct 24, 2014

What else could that have damage?

lesterl · Oct 24, 2014

Possible to damage PCM, actually anything electronic that was designed for 10-15v range, things like injectors/pump motors, etc will usually be ok, but your PCM and Radio could have suffered damage....

buba943 · Oct 24, 2014

What's the pmc?

lesterl · Oct 24, 2014

PCM (Powertrain Control Module) The computer that controls the engine and transmission, black box that sits on the drivers side fender.....

I woudl look at returning and exchanging the Alternator, tell them regulated voltage is WAY too high...

buba943 · Oct 24, 2014

Alright why would that cause my volt meter to Jume around

96 chevy tahoe 5.7 liter

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