Perplexing electrical problem... Pro-help please.
Thread Starter
Race Director
Joined: Jan 2000
Posts: 16,489
Likes: 25
From: USA. Northern Virginia
Perplexing electrical problem... Pro-help please.
1994 Corvette coupe with an LT1 motor base A/C and automatic trans. 131,000 miles. no add ons or mods 
New battery went in two weeks ago...the last one died...just over three years in age...plus I left the parking lights on
The problem: Fluxuating volt readings on the DIC. Volts will read 14.1 almost all of the time Yesterday when I was out driving the volts started jumping around from 13.4 to 14.1 never staying steady 
and The Vette tried to stutter on me once and lite up all the gauges for a nano second. I don't get a charge light at all when driving.
I drove by Auto Zone and had the battery and alt tested while on the car...they checked out OK...and the problem stopped. I retightened the battery cables and found the + cable to be a bit loose. Problem solved...so I thought.
Today when I was coming home from work the same problem started up and then stopped, only lasting a few minutes
Where should I look first...is the alt starting to die...is the rectifier bridge in the alt failing or is the starter starting to fry and drawing cuurant?
Thanks for the help, Larry
New battery went in two weeks ago...the last one died...just over three years in age...plus I left the parking lights on
The problem: Fluxuating volt readings on the DIC. Volts will read 14.1 almost all of the time
Yesterday when I was out driving the volts started jumping around from 13.4 to 14.1 never staying steady and The Vette tried to stutter on me once and lite up all the gauges for a nano second. I don't get a charge light at all when driving.I drove by Auto Zone and had the battery and alt tested while on the car...they checked out OK...and the problem stopped. I retightened the battery cables and found the + cable to be a bit loose. Problem solved...so I thought.
Today when I was coming home from work the same problem started up and then stopped, only lasting a few minutes
Where should I look first...is the alt starting to die...is the rectifier bridge in the alt failing or is the starter starting to fry and drawing cuurant?
Thanks for the help, Larry
Burning Brakes
Joined: Dec 2003
Posts: 770
Likes: 0
From: Madison Mississippi
Lets see here, your last battery just died a couple of weeks ago and you are having fluctuating gauge problems. Seems, I had the exact problem June maybe? it turned out to be my alternator. It worked fine alright, it would get so hot that it would fry an egg. I took it to a re-build shop and they said it was my rectifier bridge thingy going out. They rebuilt it and repainted it for $50.oo?? I dunno. Anyways, I clearly remember the gauges jumping around. I was worried it was my panel going out. It wasn't! Good luck.
Thread Starter
Race Director
Joined: Jan 2000
Posts: 16,489
Likes: 25
From: USA. Northern Virginia
Yea..thats what I was thinking too. I just got off the phone with my dad...fantastic car guy...he said to start at the battery cables and look for a build up of corroision...and arching residue from the loose positive cable.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Remove both battery cables (neg first). Clean both the cable lugs and the battery posts and replace the cables (neg last).
If the voltage fluctuates at idle, then get a voltmeter and measure the voltage at the battery terminals to determine if the voltage is really fluctuating or if your dash voltmeter is unstable.
If the voltage fluctuates at idle, then get a voltmeter and measure the voltage at the battery terminals to determine if the voltage is really fluctuating or if your dash voltmeter is unstable.
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
I agree
Originally Posted by jfb
Remove both battery cables (neg first). Clean both the cable lugs and the battery posts and replace the cables (neg last).
If the voltage fluctuates at idle, then get a voltmeter and measure the voltage at the battery terminals to determine if the voltage is really fluctuating or if your dash voltmeter is unstable.
If the voltage fluctuates at idle, then get a voltmeter and measure the voltage at the battery terminals to determine if the voltage is really fluctuating or if your dash voltmeter is unstable.
Race Director
Joined: Oct 2001
Posts: 12,832
Likes: 210
From: Canton GA
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St. Jude Donor '03-'05-'06-'10-'11-'12
I had a similar problem with fluctuating voltage. Here's what you do:
Get a small brass wire brush, about the size of a toothbrush. Disconnect the battery and pull it out. Behind it you'll see a post with a dozen wires attached. It's the main distribution block coming from the battery. Remove the nut and washer and carefully clean all of the terminals on the ends of the wires. Baking soda in water is a good solution (pun).
When you're ready to put all of the wires back together, spread a very thin layer of dielectric grease on each one. It should keep the corrosion from forming again.
I did this on my car last year and it's been perfect since!
Get a small brass wire brush, about the size of a toothbrush. Disconnect the battery and pull it out. Behind it you'll see a post with a dozen wires attached. It's the main distribution block coming from the battery. Remove the nut and washer and carefully clean all of the terminals on the ends of the wires. Baking soda in water is a good solution (pun).
When you're ready to put all of the wires back together, spread a very thin layer of dielectric grease on each one. It should keep the corrosion from forming again.
I did this on my car last year and it's been perfect since!
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