Bfenty

The dash lights on my 85 are out. I read in This thread that a blown tail light can do this. I do have a blown tail light, but I find that hard to believe. I see that the tail light FUSE could be part of the problem, but would a single tail light do this too?

Note: I've tried two different gauge clusters, I was told at least one of them was working, but haven't actually confirmed that myself. While it's completely possible both clusters were bad, I'm also seriously questioning if there is something else going on before I buy an expensive cluster.

billschroeder5842

Yes, if you have a "blown" tail light you probably have grounding issues. Electricity will take the path of least resistance to ground itself out and often it is through your dash/cluster.


So, fix your known problem and change out your fuse.


Your (soon to be purchased??) shop manual will have clear wiring diagrams so you will be able to trace your electricity flow easily.

Bfenty

The gauge fuse isn't blown-or is that not the fuse you mean?

I'm buying the shop manual now so I don't have to ask stupid questions lol. CD Rom is cheaper, are they in pdf format on the cd usually so I could just print it out from there? Or some stupid proprietary format?

EDIT: I was able to read the fine print on the back of the cd in the ebay listing-it's in PDF! I will probably go that route.

billschroeder5842

Not sure on your year but (if you have) your owners manual it will have a simple diagram of your fuse box.


There probably is a fuse for your rear tail light section as there is a LOT going on back there- brakes, running lights, turn signals....etc.


BTW... buy the book. It will be easier to set the manual on your front tire and flip pages while you spin your wrench than to scroll up and down while trying to balance your lap top on your knee.


Old school technology rocks.

VikingTrad3r

fenty, if you want to get started cleaning and confirming your grounding locations are all in top notch order, you can Google 1985 Corvette ground locations, and I think you will find a diagram. Off the top of my head I know there is one on the rear of the driver side head it is quite a little rats nest of cables, to get a very good view point on it you could remove, temporarily, the wiper motor but this is not absolutely necessary.

3D-Aircrew

Can you see the LCD elements when you shine a flashlight at the digital display? If so then you may have burned out lamps. If not you may have a bad power supply.

I just went through fixing my digital dash replacing faded polarizing film and changing the lamps for cooler running xenon bulbs. You can even find colored LED lamps.

You can find troubleshooting guide on youtube here:


About the FSM PDF CD if you go that route make sure the PDF file is indexed instead of one giant image file. You can't search the later for keywords or click on specific chapters.

FrostyMountain

I agree with those who say get the book, not CD. i have a CD not searchable, have ordered a manual. If you want my CD PM me with a mailing address and Ill send you mine free

bxtech

Quick and dirty way to check the ground to the cluster: Remove the metal access cover for one of the instrument cluster Halogen bulbs. Run a small wire (like 16ga) from ground, and touch the ground side of the bulb of which you removed the access plate. The cluster should light up and verifies that you have a ground issue. I've done this test on two cars I've owned in the past, and both had the same issue.

Bfenty

That sounds like an excellent method-I will try that!

Cliff Harris

It is very common for the connectors between the dash PC boards to have crystallized (broken) solder connections. The ones to look at are on opposite ends of the connectors (+12 volts and ground). A poor connection will cause the area around the pins to turn black (burned by poor connection that gets hot).

Bfenty

This weekend I think I'm going to pull the dash out and bench test it. I have a 12v power supply I can hook it up to for power and test connections. I'm pretty handy with a soldering iron so I'm optimistic I can fix it if the problem is as you describe.

3D-Aircrew

@Bfenty -- You might take the opportunity to replace the polarizing film. I wouldn't say that it is an easy job just tedious. Changing the bulbs is easy.

xrav22

Add to this the one I found at the end of my taillight harness near the antennae.
My lights did not work and I had to totally rewire them
Good luck

Bfenty

That's a good list to start with-thanks!

Bfenty

well, I have bench-tested the dash, and it works! So it's something in the car that's the issue. I think something is wrong with the LCD fuse (which the gauges won't come on without...right?). I looked behind the fuse box and there are two red wires coming out one side of it and nothing out the other side, like a wire came loose or something. I can't find one down in the dash anywhere behind the fuse box though.
You can see the two red wires going straight into one side of the same fuse here

Bfenty

also, the FSM says to refer to section 8A for diagnosing the dash electrical issues-but I can't find a section 8A! It goes straight to 8B...

Bfenty

Which side is the ground side of the light? Is there an easy way to tell?

xrav22

Mabey this helps I believe it is the large connector. I remember spraying electrical cleaner on the pins and inside the plug because it was very dirty.

TBSS/85vette

If you're having trouble with the turn signals and lights there is a connector at the base of the steering column. Check that there are no loose pins in it. That was where the problem was in my 1985. I wasted my time checking on the grounds.

Bfenty

ok cool. I'll check that out. It's good to know it's not the dash panel at least.