Temp gauge/fan help

[fusion1620]

So when I bought the 90 they had wired a switch directly to the fan and the temp gauge was not working. I grounded out the gauge and the needle went all the way up(good sign).I Hooked up the fan back to the harness and did the engine off key on test and the fans came on. Switched my temp sensor with another one and the gauge started to read but always stayed near the bottom of the gauge. When I turn the key off the gauge starts to slowly move up. When I'm driving now it bottoms out and isn't moving. I really really don't want to overheat. I have a after market temp gauge that I was thinking of mounting where they coin tray holder is. I guess it's the mechanical type.If I wire the after market gauge, will my fans work properly? Maybe splice it with they factory connection? Thanks!!!!

Just ran key on engine off test again got code 81 and stored code 33.....
Key on engine on test got 33, 73, &25. These cars really need some tlc...

 

[fusion1620]

I could use some help on this one. If the gauge goes up when I ground the wire , it has to be a bad sensor correct.?Gauge isn't moving at all now when I drive and fans don't come on..

 

[projectSHO89]

The gauge and the computer uses completely different sensors.

You have two: The single wire sensor is for the gauge, the two-wire one (ECT) is used by the computer to control, among other things, the cooling fan.

Steve