Posting since I am lost for a cause for this issue.

Problem is, the fucking needle does not read, it shakes sometimes.

So, here is what I have done.

New gauge, new probe, wired straight to battery, gave it its own ground to the body, tightened the piss out of the probe to the fitting.

Now, it doesnt really shake at all after I wired it right to the battery. It just stays in one spot, UNTIL I turn on my cooling fans via a switch, the needle moves to a different number and then stays there. I can do that all day long too, switch on the fans, the needle shoots to about 800*, turn them off, needle goes to below the one, kind of at its rest point.

Any idea's wtf could be wrong?

-MIKE-

Stroked 2.2L

you wired something wrong somewhere, no idea what but you fucked up....again!

-MIKE-

Stroked 2.2L

Just as a side not, the main gauge power should really be connected to a fused and switched +12V source... I'm not sure if yours is and you just implied it by saying "battery."

The ground issue you mentioned could certainly be a problem. I don't know what kind of EGT gauge you have, but I've taken apart a few electronic Autometer gauges in the past and the ones I've seen have very common chipsets: I wouldn't be surprised if their EGT gauges relied on AD595's (common thermocouple amplifiers) at their core. The AD595, along with most thermocouple signal amplifier chips, are really finicky about clean grounds since they're amplifying very tiny signals (on the order of a mV or less) from the thermocouple.

Another thing to consider is that the thermoelectric affect can occur at any junction between dissimilar metals. Where are the probe's wires connected to the gauge's wires? It's best if it's somewhere in the engine bay as the effect will be minimized if all junctions are in the same thermal environment.

Furthermore, remember that the gauge is reading the minuscule voltage output from the thermocouple. Any hindrance along the pathway from the probe to the gauge will cause weird readings. Make sure all connections are tight and clean. Loose connections or dirt will probably make your readings jump around with vibration.

-----------------------------------------

-Paul

Service Manuals and Guides