# Temperature gauge reading low



## Checkers10160 (Jun 4, 2013)

So last night I did some spirited driving, and now today, my temperature gauge runs low. My car also feels like it pulls harder, but those could all be coincidences. Anyways, the gauge used to stay close to 90 degree, usually a little less unless I was driving it hard, then it would be at the halfway mark. Now it stays about here. That picture was taken after pulling into my garage after a ~15 mile drive down the highway, crusing around 80. It was around the next hightest marker (A mile or 2 before I accelerated hard and the boost kicked in, trying to get into the flow of traffic, which is why it was hotter. The boost actually hit harder than I'd ever felt, and I wasn't flooring it or anything) and then visibly slid down to that position over 30 seconds or so. I don't know if it's the thermostat, temp sensor, or what but I would think if it was either of those things, the temperature gauge would be more erratic, it just seems like my car is running very cool. It was a pretty cool day with a lot of rain, but I doubt it would affect it that much. I was thinking maybe the thermostat was stuck open, letting more coolant in than is needed? Does that sound plausible, and is that the first thing I should try and replace? If not, what should I do? Thank you for any advice you guys can give!


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## sciroccohal (May 4, 2005)

*stay the course...observe*

Two things might have happened. 

1. The car was running a little cooler due to ambient weather conditions. 
2. The intake charge and intercooler mounted in front fender were also cooler. 


just watch the guage for a couple of days.


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## TTC2k5 (May 23, 2008)

Thermostat is stuck open...very common. 

cheers.


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## sciroccohal (May 4, 2005)

*what fun....*

Big fun changing it! Try some radiator flush first.


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## lite1979 (Sep 9, 2005)

I've done so many thermostats on A4 platform cars now I could do one in my sleep. It helps to have a universal-joint style socket extension. 

As long as your car's getting good heat and you're not getting an MIL (CEL), I would leave it. I just replaced my t-stat because of this same exact thing, and all I have is a new thermostat with the same exact symptoms. I suspect my plastic t-stat housing may be warped at this point, but since I never overheat and I still have heat in the car when I need it, I'm done with it.


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## max13b2 (Jul 24, 2007)

Mine has been like this for the last 7mths I've owned it and has probably been like this for a while before hand, and no CEL, hot as hell heat in the winter and pulls great. I'm leaving it as it till I have another reason to go buy the expensive G12, then I'll also replace the housing and thermo. If I sit still idling for about 5min on a hot day (like in a drive thru line) it'll heat up to midway which tells me the gauge is working fine. I think you'll be a-ok.


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## 20v master (May 7, 2009)

The gauge in the dash is a dummy gauge, meaning anything between 82*C and 98*C and it reads 90*. It could be as simple as the coolant temp sensor. Do you have the green top/updated sensor? They are ~$25 and very easy to change, as well as known for giving inaccurate readings (on non green top sensors).


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## max13b2 (Jul 24, 2007)

Not sure about the OP, but the CTS is exactly what I first thought as well, so I replaced it w/ a green top about a month after I got the car, same result. 
Note: it already had a green top in it but even these fail so I put a new one in just to be sure and its cheap.


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