Low voltage disaster... 92 K1500

[shibbershabber]

Ive got a 92 K1500 Suburban 5.7l 148k miles

So... I finally got tired of jumpstarting this thing (not my daily driver)

Had the battery tested and was shown as being bad. Alt tested good.

I found that the + post on the alt was loose. So I replaced the alternator... the battery was still crap. So I replaced it too.

Here I am, new battery and alternator. I have read some past posts and have checked the (-) cable and it checks out fine, I removed it from the stud on the intake and cleaned it up just in case. Checked continuity and all is well.

I take my meter and with one lead on the (+) post of the alt and the other lead grounded on the engine I am only showing 11.8v coming from the alternator.


What am I missing?

Also, I have been having terrible power lately. Would running 10-12v cause performance issues at all?

 

[SAATR]

Does the battery light come on with the rest of the dash lights when you turn on the key, before you start the truck?

 

[X-Cutioner]

it almost sounds like the alternator is never receiving the turn on signal
the 11.8 volts you are seeing is more than likely the battery but that sounds low. what is the voltage at the battery?


low voltage will cause a performance drop and if it gets to 9.5 or lower the computer will reset and cause alot more problems

 

[shibbershabber]

Battery light comes on before starting, then it will come back on intermittently.

Voltage at batter is the same as voltage at alternator.

Is there a relay or something that I can check? Fuse?

 

[1990rooster]

Does it start up fine now? Or weak?

 

[BigV]

Sounds like the plug on the alternator is either corroded or bad. Pull the plug, spray with some WD-40 and scrub the contacts off. Wipe it all off good and plug it back in.

 

[X-Cutioner]

the 20a gages fuse in the fuse block runs the alternator, but there is also a pair for fusable links in the red 12g wire that could have burned up. there is one on the alternator side of the juntion block and one after going to the battery

the 11.8 volts at the battery is alright for a non charging battery, the problem will be when the battery drops below 9.5v the computer and sensors in the truck will start having problems and more than likely shut down.
also i just thought of the performance issue that you mensioned before and that could be the fuel pump running at the lower voltage causing a lower fuel pressure

 

[shibbershabber]

Well I went through the troubleshooting section of my factory tech manual... all signs are pointing to a bad alternator.

But thats what I get for buying a cheap reman alternator...

Getting up tomorrow morning and going to Autozone and getting another alternator.

 

[hiredgun8]

Get your money back from Autozone. Their alternators and starters have been crap for years.
I actually tried 3 starters from AZ during 1 weekend before giving up and going to NAPA.

 

[shibbershabber]

Well it was the alternator... it failed all three tests...

hahaha getting another one this afternoon............ see how that goes.