Pyro Gyros

[Thermal Jock]

My pyro gauge is getting wierd. Whenever I turn on another electrical power source, like heater, lights, or a loud stereo, it'll start jumping around all over the place for a few minutes, then just quit all together. Then if I turn off the engine and start it back up, it works fine until I turn something on again.
I'm thinking ground, so I traced all the wires from the gauge back, made sure the ground screws were good, and traced the sensor wire back. All looks good. I replaced the gauge 3 months ago, just hooked it up to the old sensor, worked fine after that. Now do I get to replace the sensor, or could the sensor just be grounding out somehow or picking up interference?

[britannic]

If this is the non-external powered Banks pyro gauge, go ahead and unbolt, clean and remake the connections down by the engine. Clean the contacts on the actual pyrometer gauge - the Banks pyro uses a microvolt thermocouple powered system that can be very sensitive to external power sources .

Check for any chafed wires and make sure no ground/positive wires are routed too close to the pyro's wiring. YMMV, but it sounds like there may be an intermittent/weak connection that is allowing radio interference from other wiring in your truck.

[450]

Mine used to do something similar....never could get it to act right until I ran the ground wire directly to the Neg. post of the battery, no problems since then. Old truck with old wiring.

[Thermal Jock]

Thank you for the replies!
After reading them I realized I just had to get my lazy butt out there and unwire and check everything. Unfortunately, that means pulling the fenderwell to access the EGT probe in the manifold. Oh f-well. Found a small chafed area on the un-insulated wire. The probe was solid. I think it was grounding on the frame or picking up interference where it passes through a frame hole. I siliconed the hole up so the wire doesn't touch the frame. Also, the ground connection to the pyro gauge looked flaky, the wire was frayed and bluish, and had no connector. Thanks Britannic and 450, you were both dead on!
The only time I get any interference now is when I key the ham radio mike to transmit. That makes the gauge go crazy, but now it's totally stable other than that. Thanks!