Charging System Problem
Thread Starter
Heel & Toe
Joined: Jan 2015
Posts: 24
Likes: 0
From: Caldwell
Charging System Problem
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?
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
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/
Notice that 12.3V and below is considered discharged:
http://www.autobatteries.com/en-us/faqs/
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
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.
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.
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 112
From: Michigan
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.
Drifting
Joined: Mar 2013
Posts: 1,952
Likes: 239
From: Venice Cali.
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.
That's my guess from the symptoms you describe.
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 112
From: Michigan
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.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
Textbook alt wire being bad symptoms.
Drifting
Joined: Mar 2013
Posts: 1,952
Likes: 239
From: Venice Cali.
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
Good luck
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
