Help? 84 Digital Dash prob?

[Jack]

?84 Digital Dash prob?

I‘m asking this for a friend of a friend, who’s thinking of buying an 84. I know a bit about C3 ... far less about C4.

I haven’t seen the 84, but am told “its digital dash is dead.” I was asked “where is the computer that runs the dash?” I assume they refer to its digital speedo-tach cluster when they speak of digital dash.

For you folks with digi-dash repair experience ... how about offer up the first few things that are likely to be wrong when digi-dash goes dead? ... how to make repair? ... what parts it took to fix (if any)? ... where are parts? ... and approx costs?

BTW, I’m told the car’s a 78K mile coupe, garaged, OE red paint ... apparently perfect other than dead dash. Asking $4500.
JACK:gap

 

[geekinavette]

Oh those darn early C4 digital clusters.

The digital cluster has it's own microprocessor circuitry. Everything is pretty much self-contained. The only thing that comes from the car's ECM is the fuel mileage data.

There are a few common problems that creep up with these things...the back-lighting lamps could be bad for starters. You have to remove the cluster and separate the two boards to get to them. There is a board-to-board connector that gives problems frequently, but I don't know if that would cause a total cluster failure. There is also a power supply daughter-board that can fail, maybe causing a total "blackout"...not really sure if it would or not.

Check all of the fuses (inside the passenger's side door)....never know.

There are a few web sites that have some pretty good info on troubleshooting the digital cluster...have to see if I can find them again (though I'm sure Ken will beat me to it!).

Bill

 

[Ken]

Flat Dash Diagnoses

_ken

 

[geekinavette]

Not one to disappoint are ya Ken? :L

 

[Jack]

Flat Dash Diagnoses

_ken

Thanks Ken ... & you too Geek!
I read through the article ... seems quite complete without being topheavy ... author has stellar pedigree ... I'll forward this on to the prospective buyer.
JACK:gap

 

[JonM]

Here is another

http://www.batee.com/corvette/

 

[secondchance]

Hi, I had a 84 4+3 from 1984 to 1991. I don't know if you are having a same problem but just in case:
1. First, at night run the car and point a flashlight on the gages. If you can see digital readouts in speedo and tach, what you have is backlighting problem Another typical sysmtom of this is the dash will go blank intermittently at first before a total blackout. Also, at times high beam indicator or turn signals will stay on.
2. If this is the case, disassemble the cluster until you get to a fiberboard where quarts halogen bulbs are. These bulbs are mounted with heat sinks and the circuitry is embedded on the fiberboard. What was happening with my cluster was that despite the heat sinks, qh bulbs got so hot that it singed fiberboard black around the bulbs. When fiberboard siges, its carbon-conductor of electricity. In essence this was creating short circuit illuminating wrong bulbs or blacking out the whole display.

Solution is to grind off the embedded ciguitry and hardwire all bulbs to the beginning of circuit to the end of circuit for back lighting, turn signals and high beam indicator. IIts been over 10 years I made this modification so I don't recall exactly but once I figured out what was going on, rewiring was quite simple.

Good luck!

 

[Jack]

Here is another

http://www.batee.com/corvette/

Thanks Jon!

That one looks good too! I'll pass it on.
JACK:gap

 

[Jack]

Thanks vettaholic ... I'll pass that info on too.
JACK:gap