Help: Coolant System trouble shooting
 

I have searched forums for 3 days now and I cannot find solid information about cooling system. I also bought manual online (alldatadiy.com).
I have a 2002 TT Quattro AWP that recently had a coolant leak.
Coolant leak is gone but gauge reads HOT when up to temperature (running about 10min). The climatronic code ( ) for the coolant temp (49C) shows running temp at 98-104c, which should be good. The issue is the gauge on the dash is showing HOT. (gauge starts at zero and then pegs to "H" after 10 mins). UPDATE: the car has shown an overheat situation but there was no steam coming out of reservior (which I am told could not happen)

(All this was done before the above issue)The CTS (coolant temp sensor) was changed and is the suspect for the odd reading. It was changed bc of a leak.
The driver's side coolant (auxiliary) fan was also changed (definitely bad and probably was the overheating culprit but not sure yet)
I also changed the thermostat because the temp gauge was going up and the lower coolant hose to the radiator was not getting hot ( I did not use the climatronic numbers at that point). I did change the thermostat with it in the vertical position.
I am at this point were I do not know if I have a over heating condition or not...or more specifically are all my components working.

Questions for anyone who can help:
What temps do the auxiliary fans kick on? 98-105c
What triggers the auxiliary fans to kick on? (Specific components) Radiator Cooling Fan Temperature Sensor / Switch Part# 1H0959481B
What temp should the thermostat open? 88-99c
Has anyone ever had a CTS cause a bad instrument gauge reading? Yes, I did see in a few forums where this was the issue
What sensor gives an input to the Dash coolant warning light? (besides the low level in the reservoir)
What sensor gives an input to the coolant gauge on the dash cluster?
What sensor gives a input to the climate control reading from 49c?

Thanks in Advanced,
Eric

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how close to the "H" does yours read? My son just bought a 2002 TT and after a few min or so it is one notch below the "H". I did notice there is a recall out on the coolant system. would this fix the problem?

Looks like you've checked the usual stuff. Probably a bad dash cluster

Oh man, I hate to say it but I think it could be your cluster. I had the exact 100% same problem. Either internal (circuit board) or at the connector harness on the back, most likely the blue connector if the problem did lie there. Module Masters is a good company that you can send it off to. They have amazing support, I am extremely impatient and I was able to have several conversations with them and directly to the guy that was working on my specific dash too.

I do believe my gauge is not working properly or getting a bad signal. I still have a overheating issue though.
I would like to know when the auxiliary fans are supposed to come on and where does it gets its signal to come on from (what sensor). My auxiliary fans come on at 121c, according to the climate control reading from 49c.I took the thermo stat out and ran the engine and it does not overheat but the fans kick on at 121c...which seems too high. I checked the thermostat in boiling water and it did open up. When the fans do kick on the temp goes right down to 97-98ish. I have a feeling that the fans are coming on too late.

Your fans ARE coming on late. They should come on at 105c as I remember. Do both fans run when AC is on? They should. The problem can be the thermostatic switch at the radiator, the fan control module,the fuse block on top of the battery, or the fans themselves. I have had to change the driver side larger fan on both of my TTs. I also changed the fan control module on the coupe. It can drive you crazy for sure.

Yes, both fans come on during A/C operation. I am wondering if the temperature reading I am getting is correct. Because there is no steam that comes out of reservoir after the temp hits 121c. The only thing changed was the Engine coolant temp sensor (after market) and thermostat (after market but I checked to see if it worked in boiling water). I took thermostat out to check if the system was circulating water and it was. I could not get the system to overheat by revving engine or idling with A/C off. Fans kicked on at "121C according to climate control reading (49c).
I could trouble shoot this problem with ease if I knew.
What sensor does the climate control reading come from? (this is a reading you get by punching a couple buttons on your a/c heater control inside your car)
What sensor gives the coolant temp gauge on the display its reading (analog main gauge on display)
What sensor gives off the Warning light for overheating? (the light that means pull over!)
I am leaning towards a bad sensor because the car does not overheat with thermostat out and the fans kick on at 121c (I believe that is wrong). This is after about 3min of revving the engine at 2.5 rpms

I forgot to mention as I had a perceived high temp situation 121-130c on the climate control read out. I also measured the temps of the bottom and top hoses of the radiator with a laser thermal temperature reader I could not find a temp above 85c...I understand the outside of the hoses would not be as hot but I believe they should have been around 100c at least with a high temp situation. I checked this about 10 times with the lowest numbers being around 70c.