1985 display (dash)
Thread Starter
Cruising
Joined: Feb 2004
Posts: 12
Likes: 0
1985 display (dash)
My issue is as follows. For daytime driving the dash remains consistent for illumination. At night (headlights on) the dash starts to pulse. By this I mean get brighter then dims, and repeats. I keep the level low. Could this be the voltage regulator in the alternator?
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Dash ground to frame or engine, clean and tighten, or dash sensor going bad or internal dash ground, search for archive posts... you'll find alot of info
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
More likely you have the dimming circuit on one of the two circuit boards in the cluster that needs repair. The dimming circuit is fully active with the headlights on. You can clean the ground wire connection, but my money is on old age of some electrolytic capacitors on the circuit board.
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
I don't have any. Do you Vinnie?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
Advanced
Joined: Nov 2004
Posts: 79
Likes: 0
From: Richmond VA
Sometimes the ground problem is inside the gauge cluster. This was the case on my 87. There are two large circuit boards inside the cluster with a large connector between them. The ground pin inside that connector sometimes loses good contact and must be cleaned and in some cases modified to permanently resolve the problem. Here is a link to a tech article showing how to disassemble and repair the cluster. The article is from Corvette Magazine
http://www.corvettemagazine.com/1999...ash/dashp1.asp
Hope this helps!
Phillip
http://www.corvettemagazine.com/1999...ash/dashp1.asp
Hope this helps!
Phillip
Thread Starter
Cruising
Joined: Feb 2004
Posts: 12
Likes: 0
Well, I am glad to hear there others out there with this issue, not in a malicious way of course but just to know that my car does not have something really really weird going on (gremlins!). That is a good thing with forums...company!. The ground idea is intriguing, but to my way of thinking the unit seems to operate OK with the headlights off and then does this brighter/dimmer thing with the headlights on. If the ground were bad I would expect low brightness, intermittemt operation or no operation. I am leaning toward an over-voltage in the system, which would point to the regulator in the altenator I think. When the headlight s go on doesn't the alternator kick out more juice? If the regulator can't take the extra juice, it may be passing the voltage through as opposed to clamping it like it is supposed to. What do you guys think?
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
The alternator supplies the car's electrical current when the engine is running, so yes, turn on the lights and the alternator output CURRENT increases. The voltage regulator attempts to maintain constant output voltage, so if you turn on the headlights, the alternator voltage remains the same value, about 14.7 volts cold, 13.7 volts hot. Sometimes the voltage regulator will oscillate at a low frequency and you will see all the lights flicker. It can also happen that the voltage regulator won't oscillate until the output current gets to some value, like when you turn on the headlights. You can prove its an oscillating voltage regulator by unplugging the alternator and see if the flickering stops. Personally, I use an oscilloscope to look at the alternator output waveform.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
flicker
try turning off the fog lights to reduce the alternator load if the air conditioner or the rear window heater is on at night.
These high draw systems really put the alternator to the test.
Lessen the load, and the rest of the car works better.
These high draw systems really put the alternator to the test.
Lessen the load, and the rest of the car works better.
