isspro egt gauge screwing up

[WDixon27]

my truck has gone from drive it once in a while to daily and flogging up and down the road pulling a 24' gooseneck moving our shop to a new location, the egt gauge occasionally will drop to a fraction of normal readings, i played with the connections to no avail but it is not acting like it does when the connection gets weak, i discovered today when it screwed up i cycled the key/power and it came right up to normal, a little percussive investigation of the gauge itself didn't prove anything, it doesn't seem to stay screwed up for long so far and my trip between the shops is 3 odd miles so i don't know how long it takes to come back on its own as it is usually working when i get done unloading/loading the trailer (which runs 15 minutes to a hour) as it idles keeping the cab cool in the 100 odd degree temps, and it has yet to die on the morning/evening commute

 

[HBarlow]

Did you check the wiring harness connections in the A pillar up behind the gauge? Sounds like a loose or corroded connection for the microvolt pyro output or the ground wire.

 

[WDixon27]

no i haven't had time to investigate, it crapped again today as i was about to get out and let it idle down while offloading so i cycled the key and it came right back up and worked the rest of the day

 

[TRoss]

I'm watching this one, it sounds eerily similar to the problems that my identical gauge has been having for the last year and a half. Once mine began acting up it wouldn't stop until I shut the truck down and restarted it. It would do all sorts of things. It will stick at a low number like 200 no matter what I do, even if I put my foot to the floor and black out the right lane with 30 psi. Other times it will run "backward", temp dropping when I fuel hard and coming back up when I let out. Usually it would act as though it found a new "zero" and it wouldn't drop below 600 (or some other arbitrary number) even if I let it sit idling at 1100 RPM for 20 minutes. I don't mean drop slowly, it wouldn't budge from wherever it was stuck. I'm very interested in some ideas. Since I redid the wiring it seems to be doing better. I join the original poster in seeking some thoughts on this.

Could someone explain what happens with a bad ground to cause this kind of behavior?

 

[WDixon27]

a bad ground in the system could screw with the readings by the lack of a constant supply of power for the box the drives the pyrometer

 

[BHanna]

I used to have this problem intermittently. It only seemed to happen after at least 5 or 6 hours of driving but on my last long trip it didn't happen at all. I wonder if it's a bug in the control box?

 

[WDixon27]

sorta what i was thinking but i was hoping someone would pipe up "oh yea its toast" or "mine did that and i poured a bottle of coke on it and its been great for the last 9 years" :-laf, maybe being brought up by the hellish heat i have been running in all week, it has yet to screw up on the 1st trip, usually later in the day when it is over 100 but with the box under the dash in the ac that shouldn't be too much of a issue, when i run a car on the trailer i leave it running to stay cool as i will only be 10-15 minutes but if i am running pallets of crap i shut down as it will be maybe a hour to offload, so it doesn't get completely roasty toasty like now i just looked at the vent thermometer and its at 150* :{

 

[TRoss]

my symptoms don't seem to be temperature dependent. they happened throughout the winter, too.