Sounds like the LCD fuse is blown, if you can see the readings. The 4 bulbs in the cluster illuminate the LCD panels so they are bright/visible. It's possible all 4 went out at the same time, but not real likely. Stranger things have happened!
The connectors for the two cluster panels may need a good cleaning, if you have a good fuse, and the grounds checks out ok. I do have some info on the cluster circuits if you get to a point to where you need to pull it apart and have a look-see.

I too have had the same exact problem with my 1986 C-4. After days of tracing ground wires, checking fuses, throwing things and verbally abusing everything that crossed my path......I sent a money order for $300.00 to some dude from texas on flea-bay by the name of scarabexc@aol.com. 10 days later I was cruising with a bright display. I even had a big scratch on one of my lcd's and he replaced it.

happy halloween,  went out this morning and the lites all came on for about 30 seconnds and then went back to just barely being able to see everything. the tac and speedo and fuel are lookable but the numbers take some bending and twisting....I shall go and check the ground at the hush pa;nel tomorrow.  i replaced the 5 amp fuse for the lcd....seems like its a ground/short thingy...b

Hello all. Crawled under the dash today and looked around and reread the last post and could not find a bolt or nut with wires looking like a ground.  i did find a large black wire that came out of the loom and went under the carpet at the diagonal brace.  i did not get the carpet back enough to find the end but will need a little more location instruction to proceed.  I do see about five to eight wires going up above the a/c duct toward the outside at the end of the cluster. I replaced the 5 amp fuse on both the cluster and the LCD.  I am reluctant to take the cluster out until i find the ground as suggested in the post.  thanks for the help...b

I forgot to mention that the turn signal indicators are lite and the high beam center blue light is on.  they still work. 

[QUOTE=obrian] i replaced the 5 amp fuse for the lcd....seems like its a ground/short thingy...b[/QUOTE]

Is the fuse blowing, or did you just replace it just for the heck of it? If the LCD fuse is blowing, 9 times out of 10 the cluster is bad, and in need of repair.
The turn sig indicators and the hi beam lamp on all the time also point to a bad cluster...

ok, thats what i needed to know. for the time being i will drive at night with a small pen light to see what i need and then look for a repair person to fix it. thank you all for your help.  more news at 11

O.K.  You were all right. the help was all correct. It just took taking it out and apart and seeing the last post and cleaning and resoldering and putting on a short wire to double fix it and victory.  Full lights and back to normal.  Thank you for all the help and coaching.  On to the next thing....it will be in rear bearings.....obrian