I have a Westach temp gauge with a sensor in the port above the oil filter. It usually runs around 200*-220* (oil temp).

The other day it started spiking up and getting close to 300*. The only time I can make it do this is when hooked to a trailer pulling a load. I have an infrared gun and measure the rad, the hoses, the oil filter, head, block etc and everything shows "normal" temps.

At this point I'm assuming that my sending unit or gauge is faulty now. It reads ambient temps fine and boiling water fine. I reread the instructions from the 2002 install and it stresses to connect the sender ground at the same point of the gauge ground. Which of course I overlooked.

My theory is that with time, my grounding points aren't as golden as they were 9 years ago. The trailer electrics are causing some type of draw that is affecting my gauges now. Today I plan to connect the grounds together and better.

What I'm getting at is that this is the only plausable explination I can come up with. Is there any way possible that the engine oil could get hotter than the coolant? I'm talking by 50-75*? My battery is getting weak too by the way if that should offer any clues?

 

manufacturer has a spec for resistance the gauge reads, for example, 100* @ 30 ohms, 300* @250 ohms, i use radio shack carbon resistors in series to get a close value, hook it up in the circuit bypassing the sender to ground, test the accuracy of the gauge

 

I don't think 300 would be within reason. Probably not right. On a truck I had a year ago with an oil temp gauge, the highest I ever saw when towing a 5k LB camper was 226 degrees.

 

I reworked the grounds and replaced the battery. I'll make a test run today with an empty trailer and see.

If its still acting funny I'll try and check resistance although I wonder if that will work since sometimes it reads fine and then ocassionally spikes?

 

Used a common ground between the guage and the sender. Fixed everything. I hate electricity...

 

Nice though, best possible scenario for a fix.

 

True, Cheap and easy.

 

when all else fails read the instructions.

 

um, yea