Overheating reading: Bad temp. sending unit!

[b5blue]

  I had an odd problem and wanted to share it here just FYI. I totally overhauled the cooling system on my 89 Jeep Cherokee and for weeks searched for why it still ran where the temp. gauge would crawl right up to the red mark. Sure enough it was a sending unit failure not an actual overheat problem, after replacing it it reads fine.
  In many years of repairing cars I'd never seen one fail in a manner where it gave a reading 40 degrees too high! Just keep it in mind as a possibility! (The sender looks very much like the ones we use)     

[firefighter3931]

I've seen plenty go bad over the years. This is where an infrared heat gun comes in handy for diagnosing problems. If the temp reads high on the guage i simply shoot the light at the area whee the sending unit is mounted to compare readings. It doesn't hurt to take readings on the rad hoses, heater hoses, intake manifold etc...just to be sure 


Ron

[Dans 68]

This little unit is in my toolbox. Very handy. http://www.amazon.com/Actron-CP7875-PocketTherm-Infrared-Thermometer/dp/B000FJR0SG/ref=sr_1_2?ie=UTF8&s=automotive&qid=1298065257&sr=8-2-catcorr

Dan