Last time home, my Autometer pyrometer started going haywire on me. It would read normal, 800* in normal around town driving, when I pulled my camper it was about 1000*, give or take a few depending on the hills. Basically was working just fine, no different than it has for the last 3 years I've had it. Then one day when I was letting it idle down to 400* before I shut down the truck, the gauge jumped right up and pegged out where it was pointing to 6 O' clock. I let it sit and idle for a good 10 minutes and it stayed there. I shut the truck down, let it sit over night, and the next day when I started it, the gauge pegged again immediately. Stayed pegged for a bit, then went down to normal operating temp. Did this repeatedly for about a week. Then the last tiime I drove it, ( on my way to the airport to come back to work), it was fine. Wife has driven the truck since and says it is acting normal, not jumping around.
Do the probes go bad? Or is my gauge messed up? Maybe a wire shorting? I really doubt I'm getting cylinder temps spiking like that.
Any advice is appreciated and when I get home next month I'll apply whatever tips I get here and hopefully get it sorted out. Hoping I don't need a new gauge, I doubt it's still under warranty, and I don't think I still have the paperwork from when I bought it.
Oh, almost forgot, trucks fully deleted, smarty jr, gdp intake horn, ccv delete, etc. All mods are in my sig.

 

I too had a Autometer pyrometer that started acting up (needle would swing all over the gauge) after 3-4 years. I called Autometer's tech line and the tech told me to connect the ground wire directly to the battery. This solved my problem and I hope it works for you.
John

 

Thank you, I'll give that a try when I get home. Did you run the ground all the way out under the hood to the battery? Or ground it to a common ground in the cab for say the accessory power source or something?

 

I did exactly what the tech told me to do. I ran a wire from the pyrometer to the battery and connected to the to the bolt where the negative cable is bolted to the chassis, inside the left fender.
Good luck-John

 

Ok. Thank you John

 

Well, this morning I regrounded the pyrometer gauge as John instructed. Went for a ride and it worked perfect for about 10 minutes then went nuts again. Any other ideas?

 

Have you called Autometer's Tech Support , 866-248-6357?
John

 

Thank you for the number. I will give them a call. I don't have any paperwork on them anymore, hopefully it's not an issue

 

Geez, I totally for got to update this. I'm back at work now, another week to go. I am still having problems with my pyrometer. I called tech support and was told to ground the gauge independently of any other grounds. He told me to absolutly not ground it to the battery. Said it would still get interference. Told me to ground it to the engine block all by itself. So I did that. Still the same wierd stuff happening. When I ge thome I think I'm going to completely reroute the wiring for both my gauges. I have them both in a column pod. Run 1 power each, 1 ground wire each. Pull power independently for each gauge from 2 different places and see what I get. Thinking I may have my wiring all messed up. When I initially installed them, I was in a rush. Had just put in a new clutch that day, and was leaving for texas with my camper trailer the next morning. So I'm thinking I got wires all mixed up and bad grounds etc...

 

Yes pyro sensors can fail, usually they go full high or full low though. I have seen intermittant failures before. A thermocouple (pyro sensor) sends only millivolts to the gauge so any little discrepency in the millivoltage makes a huge difference in the reading. If you try all the wiring changes and that doesn't fix it, try a new sensor.

You can try pulling the sensor out and putting in it boiling water for a ~212F reading (if your gauge goes that low). You can also lightly heat it with a small torch and see how it reacts (this you need to be careful doing).

You can measure the sensor itself also with a multimeter.

Most pyro sensors are type K thermocouples, here is the millivotage VS temp chart.

 

Thanks Derek, I'll give that a shot if rewiring doesn't work. I'll remember to post updates sooner too.