wbdaily

Ive consistently had 14.7 v indicated on my dash, and I kinda figured it might have had something to do with the death of my ECM. Anyway two days ago the voltage dropped to 11.6, it occasionally drops lower and the warning light comes on but goes back up to 11.6-11.7 and out. I just put my multimeter on the battery and confirmed the 11.6. But here is the weird part, I put the multimeter on the post of the alternator and get 26.6 volts!!!! Checked it numerous times. What is going on? I assume bad or faulty voltage regulator inside the alternator, but why is the voltage to the battery only 11.6? Does the resister wire in the alt to startetr lead restrict the voltage when it gets this high?

don hall

14.7V is not high at first start-up. Should drop to 14.5V in a few minutes, and continue to slowly drop to 14.0V +/- after about 10 minutes.

Notice that 12.3V and below is considered discharged:

http://www.autobatteries.com/en-us/faqs/

Cliff Harris

Your alternator output wire is not connected to your battery. Probably an open fusible link.

Without the load of the battery the alternator can put out some weird voltages. Probably will be OK after you get the alternator-battery connection in place.

BOOT77

Could be a bad neg cable. I've been getting low volts(11's) at idle myself and started to upgrade my neg cable & some other grounds. But I got sidetracked with some suspension work, so I was never able to confirm it was my problem and I can't open my hood with the car up cause my ceiling is low. The c4 alt looked brand new on an otherwise pretty dirty engine, but I did put underdrive pulleys on it. Still my c3 was getting low volts even with a new hi-amp alt, so I upgraded that neg cable and block ground(C4 neg cable goes directly to block), then I had too many volts and had to underdrive my alt to keep wires from smoking under my dash. I read somewhere HEI doesn't like more than 17-18volts I think and my c3 was pegging the gauge with light throttle.

xrav22

Take the Alt off and have it tested just because it looks new does not mean it was previously used by someone else who cleaned their car.
That's my guess from the symptoms you describe.

BOOT77

It was new, not cleaned. Nothing on this engine was clean other than the alt and the bare alum housing has corroded some since I bought the car. Doesn't mean it can't be faulty, but I have also seen an alt tested good twice and still be the problem. I'll upgrade my ground 1st, then I'll put the stock alt pulley back on and if it still is low I'll swap the alt with a known good one.

crowz

Textbook alt wire being bad symptoms.

xrav22

You should get a new red wire I saw that mine was replaced because the guy was changing the alternator when I bought it and that is important but the symptoms you describe can't change unless you think a poor ground can work, stop working, all of a sudden wires are heating up. My thinking is still Alternator.
Good luck

wbdaily

It was the fuseable link, thanks to everyone who helped

xrav22

Was it corroded or burnt out could you please give the condition of it.
Thx

scotth48

Was this on a lt1? If so was there a loss of power due to low voltage?