Bad alternator? (94' Yukon)

[list249]

Hello everyone, new member here from Tucson. I recently purchased a Yukon, and i suspect a bad alternator, but i am new to TBI so this may be normal behavior. When cold, im pulling a solid 14v, as the truck warms up, the voltage drops to 12v. With lights and a/c running its 11v, and it seems to have nothing to do with rpm. The truck has a new 600/750 CCA battery. Is this normal behavior for a 350 TBI? Thank you.

[arcasey]

Are you reading the voltage from your gauge cluster or an actual volt meter? If those numbers are estimated from the gauge cluster I would get a voltmeter and verify them. If they are voltmeter readings then there is an issue somewhere. It is not uncommon to see the voltage drop down to 12V after the vehicle has been running for a short time, but 11V seems too low to me. I might would carry the truck to the local Autozone or Advance Auto and have them load test the battery just to verify the battery is good.

[list249]

I am reading from the gauge cluster, not a volt meter, i hadn't occurred to me that the gauge might be reading incorrect. i have already put 3000 miles on the truck with the current battery and alternator. With the key on and without the engine running im showing 10v. I'll have the battery and alternator tested tomorrow.

[Dnt]

Yeah just have your local auto parts whether it be Advance / Autozone/ Oreilly etc and they can test both the alternator and battery right on the vehicle without removing anything. takes the guesswork out.

[barry G]

1994 was the new cs130"d" alternator.

it may be the first use of four wires.

 

in this case,

it does not care what your battery is, it regulates to truck needs well beyond full charge.

this alternator was mastered by 1996 (I love it)

 

Not sure where the "F" connection would get a sense beyond battery..(in 1996 that is for ECU) someone else would have to explain.

 

You may be running perfect, just thrown off by the different way it goes about it.

[SouthernSilveradoGuy85]

From my experience if it was the alternator then the volts would steadily go down if it wasn't working at 100%. That happened on my '98. But, also even when I had my '14 the volts would read around 11 and 12 sometimes. But, if you want to be on the safe side then get an auto parts store to test it and the battery.

[list249]

Thanks for all the info everyone, i just had the battery and alternator tested, both are good. The guy at oreilly checked the battery and alternator from the battery, dont know how much i trust that machine. Lol, a few more issues have popped up, so ill be posting some more.

[list249]

Anyone know how much amperage the tbi uses? I'd like to ditch the clutch fan and go all electric, i believe the stock alternator on this truck is 105amp.