Germanskii

So I'm having an electrical issue with my temp gauge. This is a 96 Civic Si. I was having issues with the LED's I had wired into the gauge cluster, so I rewired the lights by running each LED separately to the board with a resistor for each light. I completed the work and the lights work properly, however, now my temp gauge shoots straight up to hot.

If the car is cold it takes about a minute for it to shoot up. I've checked my ECU after I had driven around for a while and my ECT showed 95 Celsius, so the ECT sensor should be fine. My fan turns on and off like normal so it's not the thermostat either. I've also tried disconnecting the battery for about 15 min to reset the ECU, no change.

The only thing I can think of is that voltage is bleeding into the temp gauge circuit somehow. I've checked the board and all my solder points look fine and there isn't any residual solder connecting the circuits together. There is some flux on the board, but it's lead free and shouldn't be conducting any electricity. Plus the temp gauge would only shoot up if I had my gauge lights on if I was getting a current bleed from the lights....unless I'm wrong about how power is distributed on the board?

I'm completely stumped as to what's going on so any help would be much appreciated,

Thanks.

mk378

The gauge has its own sensor that only drives the gauge. It is a very simple system. The sensor has a single wire. The hotter the engine gets, the less resistance from the wire to ground. So a short to ground will make it go all the way to hot.

Make sure the 3 screws holding the gauge in the cluster are tight, since they are electrical connections.

Germanskii

Yep they are definitely tight. I know there is a positive and negative terminal and that the third terminal is a switch terminal. I followed it's signal path and didn't see any issues with it, nor is there really any of my soldering work near that path

Germanskii

alright so i've hooked up a wire to the third teminal of the temp gauge (not the positive or negative terminal) and touched it to a grounding point under the dash and had no change. i checked the terminal with my multimeter and it is reading 10v, but im not getting any resistive reading at all

im at a loss of what to do...