Ok guys, i've searched this topic and found one or two threads but they lead no where. I have a 90 civic wagon, and my gauge cluster works fine most of the time.
However, (and this is usually only when the cluster gets warm/hot) The gas guage with start to rise towards full, sometimes all the way past F or just float towards the top. Whenever this happens, my tach will bounce with the left turn signal, going from 0 to whatever rpm i'm at, and the coolant gauge will bounce towards hot.
Also, the left turn idicator on the dash and the highbeam indicator both dimly light up, flashing with the turn signal.
If I use my highbeams, the high beam indicator dimly lights along with the left turn signal indicator, the tach drops and stays on 0, and the coolant gauge goes to full hot and stays untill i turn off the highbeams.
If I dont use either, the cluster is normal aside from the gas gauge. here's the kicker, If i turn on my A/C for a few mins and my cluster cools down (i'm assuming) Everything works totally normal again. I have not found any ground issues at or near the cluster or broken wires.
Here's a video of a guy who had the same issue, Mine is IDENTICAL.
http://www.youtube.com/watch?v=i2Rqxy7ToN4

I'm beginning to think the cluster is bad, but it's just weird because I can't find any reason for this. Thank you to anyone who has some insights.

 

You have a ground problem... start with the underhood grounds and go from there...

 

I have checked those, and the thermostat ground. They are tight, with no loose wiring. However, I did not directly see the ground behind the cluster that is on the dash support. I can't find it actually. I figured its a ground problem, but when I disconnected the ground on the 8 pin plug, this issue didn't happen. It just acted like i unplugged the 8-pin plug completely.

 

I just got done with the same issue mine was bad battery ground cable bro gl