2 coolant temp sensors?

[rtz]

What is the one in the upper rad hose for and what does the one in the back of the thermostat housing do?

My temp in vagcom seems to only warm up to 79 and never gets to 80 plus. Is this a sign a temp sensor needs replaced?

 

[jettawreck]

I'd replace the temp sensor on the back of the coolant flange on the left side (driver's side) of the engine first (since its easy to do and you won't lose much coolant if you can get it out, remove the o-ring, and pop the new one with o-ring on it quickly.

But more than likely you need to replace the actual thermostat which opens and closes at different temps on the front of the engine, sort of middle just below the head clear to the right side (passenger side) on the front. You have to remove the hard black plastic housing piece to get to it. You probably want to order a new housing and o-ring when you do it because the housing will probably break.

The sensor on the upper rad hose? No idea what that does, I was wondering that myself.

"The sensor on the upper rad hose? No idea what that does, I was wondering that myself."
I think it tells the fan(s) when to come on/off.

 

[2002MK4]

Jettawreck - pretty sure you are correct...that's the one that activates the fan.

RTZ - So the coolant temp. sensor failure is as follows...you are driving, car heats up just fine, few minutes later your temp gauge goes to "C" in the middle of driving.

York77777 - Coolant temp sensor was a pain in the arse for me. That o-ring was what took precious seconds of time to remove while most of my coolant leaked out...argh!

 

[jayb79]

Isn't the a sensor in the radiator for the fan temp?

 

[Dana Hanchett]

Sensor in upper radiator hose is for shuting off air conditioner if coolant temp goes to high. This is to help cool down the motor in an over heat condition. Hope this helps.

 

[jettawreck]

Sensor in upper radiator hose is for shuting off air conditioner if coolant temp goes to high. This is to help cool down the motor in an over heat condition. Hope this helps.

Thanks for the info and the correction. Now if I can retain that information, or at least remember until its asked agin.