Hi there I just got my 90 civic si 2 door hatchback about 3 days ago. My temp and rpm gauge work every now and then and the fuel gauge doesnt work at all and the speedometer works perfect. From what I can tell the previous owner put in a headlight switch. when i turn on my blinkers (either way) the rpm and temp guage tick with the light. When i have just my dims on all three go all the way up, when brights are on they might work or might not just depends if they want to i guess. I am willing to take dash apart if i must i just would rather not so would love help from anyone. oh and blinker lights wont work sometimes.

 

check grounds, check what the other guy did, find the diagrams and keep going.
the cluster diagrams are somewhere online. good luck