Temp gauge or sensor?

[Shelby789]

I have noticed recently that the temp gauge on my TDi will climb well above the 190~200deg. F range and creep toward the 230.....turning on the heat or AC doesn't seem to budge the gauge, but it will always suddenly "Jump" from 230 back down to 190 in a second or less.

I thought I might be looking at a faulty temp sensor, but when I went to pull it last night, I noticed it looks unusually clean, I think the previous owner may have already been down this road.

I am looking for direction on telling the difference between a bad sensor and a bad gauge? Is it possible I am looking at a bad t-stat that opens late, the speed with which the gauge goes back to "normal" makes me think I am looking at an electrical issue and not a t-stat issue?

 

[mrorganic77]

Just my opinion but i would replace the Thermostat as that is what is sounds like to me and that is cheap. When the thermostat opens it would drop the gauge that fast as its been holding all the coolant back.

 

[schultp]

+1. Thermostat.

 

[G60ING]

Thermostat or coolant level.

 

[Shelby789]

Just to wrap up the thread, I finally got around to hooking up the Vag-com to the car and when the gauge reads 215 deg. f the vag com registers 87 deg C (~188 deg. F). So either the gauge is crap, or the sensor is no good. I never got the gauge to read in the 230 deg. range it was previously, but I am confident that the car isn't actually getting much above 205 deg. F.