94 GT Help Getting Frustrated

[tankard]

OK I bought a 94 GT with about 175k miles on it. It had an alarm system and a new stereo installed by the previous owner. When I bought it the gauge cluster needles were somewhat flickering. After a few days the weather warmed up significantly (33C) and the water temp gauge started showing that the car is overheating - it would go to red, the drop a bit then drop to the middle go back etc. So I bought another gauge cluster and replaced the old one. This fixed the problem for about a day and then it started showing that the car is overheating again. SO I put in a new rad cap and a 180 thermostat. THat didn't seem to help. I had the coolant checked at a shop - diddo. So I bought an autometer water temp gauge and wired it up on a switch, separate from the ignition. TO explain more in detail, I have a wire running from the battery to a swich through a fuse and from the switch to the gauge. THe ground wire is hooked up to a screw i found underneath the dash that is screwed into metal.

Now here's the fkd up part:

When I drive the car it shows i'm running around 230F after warm up. But if I turn the car off it goes back to 195-210. If I press the brakes with the car off, or open the door, or turn on the interior light it goes up to 230 again. THe moment I turn the ignition on even without the engine it'll jump up to 230 again (with the engine warm). Occasionally, as I'm driving I will hear a popping sound from my speakers and my stereo resets, the dash gauges bounce around (oil press and volts) and so does my autometer gauge. It is also worth to mention that I also installed an oil pressure gauge but haven't put the sender in yet so It's just wired for power and light. THis gauge does not move around like my water temp gauge.

Now first of all I have no clue if i'm overheating or not.

Second of all what the hell is up with my electrical system???

Please I need sound advice I've tried other forums but have not had any help.

[SpectorV]

when you installed the gauges where did you run the wires to power them to? did you use a relay or splice into existing wiring etc etc.

[tankard]

the power wire is running straight off the battery positive terminal through a fuse to a switch

[hottcobra]

check to make sure that the engine itself is properly grounded. it sounds to me like you have some back feeding issues caused by a bad ground. make sure that the engine ground straps are tight and clean

[tankard]

thank you for that. I was thinking about it so I went to the garage and religiously cleaned out my battery terminals and the ground wires (new screws). Well what do you know everything works a-ok and the car is not overheating

[MonteCitan]

Aside from the wiring... Any chance you could hook up a mechanical water temp gage?

[hottcobra]

anytime. I try to help whenever I can