My 1987 nissan 300zx's digital instrument cluster wnt light up. why?

wiring diagrams.

my guess is that since you hit a bump in the road that its possible that a plug has come loose from the back of the dash.. remove instrument cluster and inspect for loose or broken wiring and connectors..

Check your alternator. Autozone can check it for free.

what are the biggest size rims i can fit on 1987 nissan 300zx without cutting frame?

if fuse and relay good sound like fuel pump going out.

brake pedal switch see if you have power on both sides of the switch when the pedal is pressed and activates switch.

Order one from www.courtesyparts.com (Courtesy Nissan in TX) - they were great for all the years I had my 90 300ZX.

Check water temp. sensor. Top front on water pipe, connector with two wires. One wire connector next to it is temp gage.
Green corrision on connectors in engine bay is big problem

Its the connection to the power supply module that is connected to the intrument panel. Its about the size of a cigar box and is silver and is left of the stereo. you will need to remove the panel under the steering colum to access it. wiggle the harness that goes from the inatrument panel to this power supply module until you instrument panel works again. i don't have a permanent soution except to buy a new panel. I am dealing with the same problem.

I would think that the brake switch which is connected to the brake pedal might be damaged, causing it to always have contact. They are usually not very expensive. Please rate this if it helps. Thanks.