I'm trying to understand how the engine and transmission temperature sensors work on my cat 955l. Appears that there is only one solid copper wire coming from the sensor to the gauges. Anyone able to help me understand how they function?
They're what's known as capillary gauges. The copper wire is actually a small bore tube connecting the gauge to a little reservoir containing a liquid (alcohol maybe?) As the temperature changes, so does the pressure in the reservoir and the gauge registers the change in pressure.
If that tiny little tube gets a kink in it the sensor and gauge are shot. Usually the tube is wrapped with a spring to help prevent this but not always. Be very carefull with the line anytime it is moved.
I believe the liquid in most is actually ether. And if you are real handy and adventurous you can try to fix a broken one! http://www.ply33.com/Repair/tempgauge
I replaced all of mine and the hardest one was on the torque converter, harder to get to but easy enough
Appreciate the responses. I reckon I'm going to go ahead and replace both engine and trans gauges. Alldodge, did you go with aftermarket when you replaced yours?
I went with CAT on the temp sensors, used after market for oil pressure and amp meter