C4 Instrument Cluster lights out & both turn signal lights on
 

Why did all the instrument cluster lights in my 1987 suddenly go out while both my turn signal lights came on and remain that way? In the daytime, I can see that the entire instrument cluster display is still working, but not the lights. The turn signal lights work fine as well as all the head and tail lights. None of the fuses inside the passenger door area are blown. I replaced all the instrument cluster light bulbs only a few months ago since two had burned out. I checked one of the lights by putting 12V to it, and it works fine, so I assume all the rest are good as well. So far, I don't notice any other problems. What circuit is involved?

Your symptoms are caused by the loss of the ground connection out of the instrument cluster. This ground (black wire) is connected to ground behind the instrument panel near the left hand side of the steering column and is G201. When this ground opens, the backlight bulbs pass current through the turn signal indicator lamps to ground. The turn signal indicator lamps are connected in parallel with the turn signal lamps and these lamps are grounded. The turn signal indicator lamps draw so little current that their current will not light the instrument lights or the turn signal lamps. Find this ground and correct the grounding, probably a loose screw or corrosion.

Hi.
It is correct that it is the ground that is missing. I had the same but it was not the external ground from the cluster but inside it. Here is a step by step solution on how to deal with the internal problem. http://www.batee.com/corvette/
To check if the external ground works use an ohm meter (multimeter) and confirm that there are connection to the connector for the ground. Be sure that you use the right pin so that you do not ohm directly into the hot pins of the ecm.

Always disconnect battery when dealing with these electrical matters
good luck

:iagree: At least you got the simple fix. jfb helped me tremendously during my dash light outage. There are lots of steps and power/grounds to go thru until you can finally solve the problem sometimes. Take the dash out and there are two connectors. There are three black wires total in the two connectors. I took an 18 gauge wire and soldered it into each and combined them into a 12 gauge wire and took it thru the firewall to the frame ground at the battery. This didnt solve my problem but it eliminated the grounds as an issue.

Jan-erik has given you the definitive link on dash problem solutions and a lot of other Vette knowledge. There are some great folks here that have spent a lot of time creating data bases and are willing to help out.

Good luck!

Thanks for the info, but don't see any black wire (ground) connection that visibly comes from the instrument cluster connectors on the left side of the steering column. Tried removing the instrument cluster to clean & resolder connections without improvement. Can't find the G201 ground connector. I've also read that a G401 ground connector might be involved but can't find that either. I may be off to the dealer for repair.

I discovered that the plastic shield surrounding the multi-prong female connector had melted just enough to prevent full contact of the male connector which happened to be the ground. I was using "recommended" light bulbs that were too bright and thus too hot which caused the melting. I cut a small piece of solid wire and placed into the space made by the melt. This appears to have solved my problem since it's been several weeks without a glitch.

Sooner or later it will fail. I understand that the S-10 has a connector at the ECM which is the same 32 pin one you need. Its a pigtail so you will hafta do some modding. you may also find one of the rebuilders here may have a dead board they may part out.

I just fixed my panel yesterday. It had the same symptoms as yours. Mine was bad solder on the connector that connects the two big circuit boards. You must take the panel apart to fix but it is an easy job just a lot of screws to remove the boards from the panel. Look at the male connector with a loupe or magnifying glass and you might see that the solder has separated from the board and the post of the connector. I cant remember but I think there are 12 to 15 post on the connector. Resolder all of them adding some new solder.
This site http://www.batee.com/corvette/ helped a lot.

Bought a C4 without an owner's manual, and my wife went out turned the lights on and the instrument lights went out. She had to come home with no speedometer in a strange car with multiple radar cameras.
I found this thread and thought Bryan Thompson's information was probably the best documentation and help I'd seen in 40 years with road and race cars so I've sent him a donation. Probably the only place in the world you could get that information, and a long way from Australia.
I was lucky, didn't realise there was an instrument panel dimmer on the light switch. The panel lights are fully bright at full anti-clockwise rotation of the light switch, but it is so sensitive they go out after only a small turn clockwise. What my wife did when she pulled the lights on was accidentally give it a fraction of a turn to the right and out went the lights. I turned the knob fully anti-clockwise and on they came. Better to be lucky than rich because this is a right hand drive conversion and I never did find the earth.

same issue
 

Did you get this resolved? Fix?

Turn signals and high beams stay on but dash is barely visible
 

Mine did the exact same thing, any luck fixing it?

The OP has not been on site since 2016 and Chrysler66 since 2018. You should start a new thread detailing your issues.

Good question worthy of a new thread.