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I've scanned the archives to see if anyone else has posted this problem but could find nothing similar. V70 has 48,000 miles on it and yesterday suddenly the external temperature gauge started showing very high temperatures. Now I'm used to the fact that the temp gauge shows hotter than the air temp when the car has been sitting all day on hot asphalt. But this was different.
I had just completed a 250 mile road trip in 80 degree midwestern weather and then left her to sit for a couple of hours in the sun. When I returned to the car and began driving 20 mph down the street with the AC on full (Set to auto, external air button selected rather than the recirculate button), suddenly the temperature gauge began skyrocketing to 115 degrees.
Over the next couple of hours (during a return version of the same 250 mile road trip), I discovered that turning off the AC would drop the gauge back down to approximately 91 - 93 degrees...understandably, less strain being placed on the engine could be the reason. If the car was moving in the 60 - 80 MPH range, the gauge stayed at 93 degrees occasionally dropping down to 88 or 89 -- though the actual air temp was in the low 80's. However, if the car slowed to a crawl (traffic jam) the temp immediately started its upward run again into the 110's even with the AC off.
The engine temperature gauge did not seem to be affected as it stayed in the position of 4 bars below the first bold high temp mark - just slightly above the middle mark. I state this just in case anyone asks if the engine was overheating.
So what gives? Is it just heat from the engine cooking the temperature reading or do I have a failing gauge or (I'm afraid to ask) is this a symptom of something more serious? I could understand if this is just the gauge picking up heat from the engine especially when the engine has been running for a couple hundred miles at 75 mph and the car is now sitting on hot asphalt. But is that what's really happening here?
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