Hello everyone, I'm new here. Right to the point...
I have a 87 cimarron and the digital instrument cluster quit working. I have the factory repair manual and I'm getting good ground and power all the time and switched power is good and dimming power is good.
What goes bad in the clusters when they stop lighting up? I would much rather repair the circuit board vs swapping the cluster. Hitachi america which is the manufacturer, was completely usless.

Now here is a technical question for the guys that live and breath j bodys... my cluster is made of BLUE plastic. All the replacements are made out of WHITE PLASTIC.
When the first cluster went bad 10 years ago someone told me that the white and blue were not interchangeable. I cant remember what they said. Now when mine went bad 10 years ago I bought a blue one from a yard in texas. Now I'm looking and all I see is white plastic ones. Please tell me what the color signifies..

Is your dimmer just not working when you turn your lights on, or does the panel just absolutely not illuminate/"turn on" when you start the car?

I would first check connectors and connections. Get them clean and bright on both the cluster and the plugs. Sorry if you've already done this, but spending the time to do this is very important. Also, make sure those plugs are nice and tight after you plug them in. Any looseness can cause problems. I don't think this is your problem, but this is always a good start.

I would then start digging into the cluster if the above didn't solve the problem. Old circuit boards and traces are very susceptible to corrosion. Any water or electrolytes from failed/leaky capacitors can absolutely eat through a trace and break a connection. Double check solder joints, especially closest to the plug ends. I could almost guarantee that you have a problem like this, especially if you're already seeing good power and ground at the plug. 8 times out of 10, an electrical component just suddenly crapping out like this typically means a broken solder joint or failed trace. Just my experience though. I'm not an electrical engineer or anything. Just a regular dude.

Lastly, there are some digital dashes available for sale at a few junkyards around the country. Check hollanderparts.com I just recently spoke with a yard in New Mexico (I think) that had a digital dash for sale. I want one for my 1st gen sunbird, but am not interested in the wiring headache the change would require.

Thanks for the input Dave. I've already done what you suggested. Also the entire cluster does not light up.