I suspect my pyrometer system acted up recently and was reading low as I climbed the west side of the Oregon Blues with the 11 1/2' camper on my 91 F350. I remember thinking at the time that the temps were sure staying lower than usual for that climb. I think things may have gotten hot enough to cause cracks in both heads even though the gauge didn't read much above 1000 because after the trip I noticed the temperature at idle seemed really low and when I jiggled the wires in back of the gauge the reading jumped nearly 300 degrees.
The engine work is underway and I want to check the sending unit and the guages. I checked all the wiring and didn't find anything wrong. Turbo idle temps were reading normal just before I pulled the engine but I don't trust the pyro system.
1. Is there a way to check the accuracy of the pyrometer?
2. Is there a check for the sending unit?
3. A new pyro and sending unit would be cheap compared to what these heads are going to cost me, however I don't want to be tossing more money onto the pile if I don't need to. With over 140,000 miles since the turbo was installed should the whole pyro system, wires and all, be replaced?

Thanks! Don

 

check the milvolts on the probe see if it goes up and down with the meter . or just stick the probe in boiling water 212 degees