Peculiar Voltage Issue....
Thread Starter
Intermediate
Joined: Mar 2007
Posts: 36
Likes: 0
Peculiar Voltage Issue....
Ok, so just recently I've started having this issue on my 89. I'll start it and the voltage is sitting at 11.5 indicating no voltage from the alternator.... UNTIL the car warms up to about 155 and the idle changes. It's been pretty consistant with coolant temp. It jumps up immidiately to 14.4 ish. Usually won't have any more issues for the rest of that day. I don't know where to even start with this! 
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 1
From: Huntington ma
I've had a similar problem, although not with a digital dash car. Old chevy pickup that does the same thing, won't show any charging voltage until it warms up - until the Dash/interior warms up. The problem was the voltmeter itself - an analog "mechanical" gage. I doubt that such a problem can happen with the digital dash, but...
If you connect up a battery charger and Force the voltage to go up does the gage display show That correctly?
If you connect up a battery charger and Force the voltage to go up does the gage display show That correctly?
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
Ok, so just recently I've started having this issue on my 89. I'll start it and the voltage is sitting at 11.5 indicating no voltage from the alternator.... UNTIL the car warms up to about 155 and the idle changes. It's been pretty consistant with coolant temp. It jumps up immidiately to 14.4 ish. Usually won't have any more issues for the rest of that day. I don't know where to even start with this!
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
Remove the side panel then the battery to gain access. Just a warning this is a time consuming task the tar sealant they used on these connectors is a PITA to clean/remove. No doubt the "tar/sealer" will have crept into the connections. You want to pick up a big can of CRC electronic cleaner and/or some alcohol along with about 300 Qtips. And some RTV to reseal the outer portion of the connector so you don't get H20 intrusion in there. Most of the electrical connection for the interior go into the cabin through this 41 pin plug. Take your time with this task.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
If the alternator isn't charging the battery, your red battery symbol light should be lit on the dash. I suspect a dash voltmeter problem. Use your VOM (voltmeter, ohmeter, milliameter) test meter and measure the voltage across the battery terminals and compare it with the dash voltmeter. Engine cold, the alternator output voltage should be close to 14.7 volts and it decreases with increasing alternator temperature and fully warm, the alternator output voltage should be close to 13.7 volts. If you had poor cable connections to the battery, you wouldn't be able to reliably crank the engine to start it.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
7 Bolt-On Upgrades From Extreme Online Store to Level Up Your C6 Corvette
Pouria Savadkouei
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Disconnect the ground cable from the battery and measure the resistance from the battery positive terminal to the alternator output terminal. It should be the same as touching the ohmeter probes together. This tests the fusible link in the alternator output terminal.
Check the gages fuse and the c.fan fuse with an ohmeter. Another possibility is a broken wire inside the alternator on the output terminal. Rotating the output bolt can sever the inside wire and it can be intermittent. Last, remove the alternator and have it tested.
Check the gages fuse and the c.fan fuse with an ohmeter. Another possibility is a broken wire inside the alternator on the output terminal. Rotating the output bolt can sever the inside wire and it can be intermittent. Last, remove the alternator and have it tested.
