Pyrometer gauge problems

[jzilla]

I have an auto meter pyro gauge. All of a sudden yesterday the temps it was showing were not correct. The temps would not go above 500F. As soon as I parked the temps would be at 200F right away. Anyone else have problems like this? Seems to me this is the gauge and not the probe, I'm not sure though.
thanks,
john
I have had it for about a year I can't find the receit though arhhhhh.

[cruiser_guy]

John, I'd check connections and ground. Other than that, I can't help much as I have only used the Isspro gauge.

[wesintl]

Like above. Check the ground. Also check the positive connection. Mine operated the same way when I didn't install it correctly.

[jzilla]

I will check those things, it has been fine for a year though then it just went funny.
Although once or twice before the needle would kind of shake.

[brownbear]

connections should be super clean. use a little scotch brite or fine sandpaper to clean.

if your probe came loose it is possible it got damaged from the vibrations. To me it sounds like a probe. Put a meter to the probe. see what you got. it should be not too high. Possibly 1-6 ohms. That is purely a guess on the ohms. I am used to aircraft reading .7 ohms across the egt probes.

So you might be under a ohm. The hotter it gets the higher the resistance.

You could test the probe by disconnecting the lead wire, hook up your multimeter to the probe wires and use a heat gun or other heat source. The probe needs to be out to do this.
If your resistance goes up and up as you heat more then the probe should be ok. Your need to hook up the meter in a loop for continuity.

Also if need be you could buy a second pyro and just try the guage with out butt splicing or anything. if you are gentle you could find out if it was the gauge or not. If not you could then return the guage to the store. If you were gentle. My way of thinking anyhow. You could not do that to a probe, the heat will make it all discoloured. So you could not return that.

Good luck.

[jzilla]

I am buying new gauge tomorrow, I will try it, if it does not work then I can bring in back to store.

[wesintl]

Oh.. Hey make sure the connections are offset and not close together where the guage wires and element wire meet. Mine were close but not touching and under shrink wrap but it was creating signal problems reading.

[jzilla]

Tried new gauge but same problem. So I am getting new probe. Problem is Lordco has to back order it, 4 weeks til i get it!!!

[cruiser_guy]

John, are you sure there is no shorts in your lead in wire?

[jzilla]

By lead wire do u mean the main power source? How would I find out? I run a fuse it has not blown.

[cruiser_guy]

John, disconnect the wires at both the probe and the gauge/transducer and ohm out each wire. If any wire has a reading other than infinity with regards to the truck chassis, you have a problem.

[jzilla]

Ok not sure if i did this right.
I took a reading set at 20 on the multimeter between the two probe wires and got a reading of 4 ohms.

[silvercrusher]

There should be resistance across the probe like you have i'm not sure what the actual numbers are for your probe but that sounds reasonable aboutthe same as a glow plug. As the probe heats up the resistance increases so now check when its hot and you have the probes range.
I think he meant to check each wire individually which would indicate a short on one if it were not infinity.
So you would have to put one multimeter probe at one end of the wire and connect the other to the opposite end of the wire that should tell you if their is a break in the wire or a ground.

I think?

[cruiser_guy]

Nope, I mean disconnect the probe and the transducer both (so the wires don't connect to anything at either end) and measure resistance between each wire and ground. There should be infinite resistance. If not a wire has chaffed through the insulation. You could also ohm the wires end to end as "silvercrusher" is suggesting but I doubt there will be a problem there.