Thermostat or Temp Sensor??

[mancdan]

Hi all. I have had my 2.0 Tfsi for just over a week and noticed the temp gauge taking ages to get up to the 90 mark, probably 20 mins at least.
Once it gets to 90, it will stay there if I am driving around town.
However, as soon as I go on the motorway it drops to halfway between the 50 and 90 mark.
Once back in traffic around town, it will creep back up to 90 once again.

Am wondering if its a faulty CTS or Thermostat.
I know the CTS is the easy fix, £42 for the part from Audi and a few mins for me to swap. (although Audi said there were three options for this part - so just need to find out which one it is)
Thermostat is also £42 but I would probably ask my local garage to fit, so £100 in labour.

Heater seems to be fine and blows nice hot air.
I also noticed my Air Con on low was barely cold over the weekend, but don't think this will be related as it may just want re-gassing.

Any thoughts peeps?

 

[Dani_B19]

Probably the thermostat.

I changed the cts hoping it was that but didn't fix the issue. I'd just change both for piece of mind.

 

[Frank_UK]

My issue was the thermostat. I hardly drive much in town (though when I noticed the issue I went for a spin locally for a while and it did reach 90) but generally the behaviour on motorway was the same as yours. The temp gauge would also move depending on whether I would go up or down a hill.
This was during winter and the heater was blowing nice hot air too, so no indication that side. The gauge should sit dead centre at 90 once operating temps have been reached and since mine has been swapped it does exactly that. Fuel consumption has come down again too.
If you have access to VCDS mine came up on the scan as faulty and costs on par to what you have projected.

 

[mancdan]

Thanks Dani_B19 and Frank_UK.

 

[Dan burns]

most likely your thermostat was stuck open,mines was doing the exact same thing ,changed it and the problem was sorted

 

[mancdan]

Cheers Dan burns. Got it booked in this Friday with the garage that sold me the car to have them both changed (at no cost to me)