heater on slightly, outside temperature reading too high

I am not yet convinced that what I am seeing is real, but my 2007 of late seems to be reading the outside temperature too high, and when set to just blow air there is warm air coming out of the vent in either recirc or fresh positions (with T-inside set lower than T-outside). For the first one, this afternoon it was reading 85 when it wasn't more than 75 outside. The car had been in the sun though, so maybe the metal around wherever that sensor is located was warm to start with and stayed warm? Drove it 10 minutes, parked it for 5, drove it 10 minutes more and it was still blowing warm (not hot). Same outlet temp (as judged by feel) for either recirc or fresh positions. Is there a condition where the heat can get stuck "a little on"? A car which has been parked in the sun for a while will tend to blow warm air, but 20m of road time would seem like enough for it to cool off, yet the vent temperature seemed to be pretty constant the whole time.

 

No. When it was reading 85F outside the temperature was set to 75F.

 

Will do next time it is driven. The A/C still blows cold when it is set to do so. Cannot rule out "whole lot of cold air + a little warm air" though!

 

Today we took an instant read thermometer along for a ride. The outside air temperature (in the shade) was 75F. Started the car and it read outside as 78F and continued to do so during the drive. The vent temperature when moving was 87F regardless of the temp setting at "low" or 75F or flow on vent or recirc. The cabin temperature was also 87F. Turned the A/C on with the temp set at 75F and with a low fan and it blew cold air into the cabin. Did not measure that temperature though. The grate area ahead of the windshield on the passenger side where the air comes in (I think) was in the sun most of this time, and the plastic there felt pretty warm. So I'm still not sure. It seems like the heat is "a little on" but I cannot really rule out that the section of the car where the hot air moves isn't just hot from the sun and that that is what is causing the warm vent air.

 

Is there a valve that does that? The only one I know of in the coolant path is the three way valve that shunts hot coolant to the storage tank, and I thought that always sent to one or the other, not to "off".

Seems more likely that whatever door/actuator that controls air flow over the heater core might not be moving all the way shut/open (whichever way this goes) so that it is blowing a little air over the core when it shouldn't. There is some mechanical device under the dash on the passenger side which makes slight groaning noises when the car turns on, perhaps that is it?

That said, this morning it was 65F out, the car had not been in the sun, and the air out of the vents felt very close in temperature to the outside air. No thermometer along for this ride to provide actual numbers though.

Makes me wonder if what I saw previously was just the result of the car having sat in the sun for a while. Searching through the heater related posts in this forum there are quite a few about no heat, none so far on this issue.

 

On Saturday it was moderately warm (mid 70s) and sunny when we drove to a store about 10 miles away. The car sat in the sun there for roughly 30 minutes. Start it up and start to drive home and it is blowing hot air again. No thermometer with us but it was probably around 85F. Circulation is on vent (not recirc) temp set below ambient, A/C off. This time I just opened the back seat windows, left the climate control as it was, and kept driving. After roughly 10 minutes the air coming out of the vents finally dropped to ambient temperature (5 minutes on surface streets, then 5 more on the highway). Of course the car was in full sun during that drive too. So either the heat somehow sticks on for a while when the car is cold or something in the air path gets really hot when the car is in the sun and it takes a considerable amount of air passing through it to cool it off.

 

The car still has this issue - fresh air out of the vents significantly higher than outside air temperature for at least 10 minutes. A/C works fine, this is just moving air from the outside and out the dash vents. In all of the following the A/C was off, the fan was at half speed, and the air was directed only out the dash vents. The car was parked in the sun in READY.

Ran Techstream and checked for codes, none other than the inevitable B1421 (the solar sensor).

Put a mirror and flashlight near the gas pedal so I could see the lower actuator armatures. Started at MAX COLD and increased the temperature, nothing moved until it got near the outside temperature, at which point the plastic moved a lot, the ICE started at some point (was looking down at the time) and stayed on to MAX HOT. Running the temperature down in the other direction had the actuator armatures in the same positions (more or less) for the same setting. If there is hysteresis it is small. The actuator seems to be working normally. (It doesn't make any noise, it moves smoothly.)

Employed a handy dandy meat thermometer. Waved it out the window. It read about 74.5 and the car showed 75. Pushed it into the driver's side center air vent and it read 88.7 F. This was after a couple of minutes at MAX COLD. Put the thermometer probe through the crack between the hood and the body near the driver's side edge of the air inlet. It read 89.0F. The probe was too fat to stick through the mesh over the air inlet.

All of this is consistent with the air inlet heating up when it sits in the sun and then it transfers that heat to the fresh air that is coming in. What is surprising is that it takes so very long for that incoming air (at 75F) to cool off the inlet path, and that the inlet path heats up the air that quickly. Also, how can the car tell it is 75F outside if the air it is sucking in is heated to 88-89F in the inlet? Is there an outside air temperature sensor which sees a different source of air?