I have an autometer phantom pyro that bounces around. It only does it in the afternoon on the way home from work. Sounds silly but thats the only time it does it. It acts llike it has a bad ground or a loose connection. I have checked and re-checked and all is tight. Sometimes it will fluctuate the full range of the gauge, sometimes it acts like it runs about 400* cold, sometimes it just pegs out at the 5 o'clock position. Im stumped. Any ideas?

 

Does it seem to react to road conditions? Does it seem to react more in a certain expected temperature range, say expected 650 degrees while cruising steady state load?? Do you have a DVM that you can read the mV from the thermocouple to see if the input is stable?

 

Sometimes it will act like it wants to move if I hit a bump or something, but not always. What is a DVM and how do I read mV? Speak english man!

 

DVM = Digital Volt Meter
mV = milli Volt (1/1000 of a volt)

A DVM can be had for a reasonable amount at Sears and can be used for many trouble shooting efforts.

mV is the signal that comes from the thermocouple.

Use the DVM to check for a stable signal and to make sure it is of a value that matches your gauge.

 

I have a multimeter, know how to use it, will check for signal.

 

make sure your connections are tight and they are seperated good i had one do this they were rubbing on each other

 

also check where the hard line of the probe comes out of manifold and the braided wire starts. Let your truck idle and have someone watch your guage and wiggle the braided wire at the probe and see if the needle moves or jumps. I had one crap out there.

 

Mine just started doing the exact same thing, sometimes it works fine and get temp readings in line with expected norm, other times it will peg the needle other hot or cold, sometimes it just bounces around. I'm leaning towards a defective probe or ground problem due to the fact that turning the headlights makes the problem worse (when its not working correctly). When the snow stops Im tearing into the wiring, hopefully Ill find something.

 

my autometer used to bounce all over the place about 2 years after i put it in. i cut the shrink rap off of where the probe wire conects to the wire that goes into the truck and what had happed was 1 of the bolts connecting them loosened up just a little bit and rusted in between because the heat shrink from auto meter didnt shrink tight enough. all i did was sanded off the rust put 2 shrinks 1 on each wire then a big 1 over the both of them and never happened again.