I have a 2003 A4 B6 1.8T. The air temp is not the same at the 3 possible level. Windshield 46C, face 31C, and feet 19C. I've check it with an infrared thermometer but only with an hand, it is visible.
I took multiple mesurement at multiple time and external temperature. there is Always a verry big difference between the windshield temp and the foot temp.
When I buy the car, 1 month a ago, they change the coolant, so I don't know if it was ok before. No difference if the air rush throught the 3 outpout or only one. More volume but not more temp. It's the same for driver or passenger, there is a difference. The fan speed change nothing to the temperature difference between the outlet.
Even if I ask it to do Max or 22 or 20 with the same fan speed (5), the air is not hotter at my foot.

The thermostat work well, I can see it opening will checking it's reading with my code reader. It open around 102-105C then the temp of the coolant drop. this is Normal.

other mesure: up:24 face:22 feet:10.
41 34 24
27 9 1

am i alone?
How can this be possible? all the air is supposed to pass throu one heater then it go where we ask it to go? Is there 3 heater?

 

Probably a combo of a lot of things. Heat rises up of course, the glass will absorb heat from the sun and if it's a laser IR thermometer then using them on a shiny or reflective surface makes for a fair bit of inaccuracy I believe. Just a few things to consider in your experiment.

 

I'm talking about the air that come from the ventillation. Even with my hand, I can feel with not doubt the difference. My girl friend too. Difference confirm with a thermometer. There is 3 way to blow air in the cabine, windshield (up/defrost), middle (face) and at feet. Did your car give the same air temp at every outpout?

 

I can't say I ever measured the temperature of the air in the car. I guess what I'm saying is that there are many factors than would cause a difference between the various vents. I wouldn't expect them to be all the same. Another possibility for the low feet vent temp could be that there is a air flow restriction of some kind? A blockage or not opening fully? Something else to consider.

 

I have also noticed that the heat blowing from the floor is cooler than the others... I wondered why, but havent bothered to look any further.

Chad

 

I have the same problem.
A heater core flush fixed it ( 115.00) temporarily, but then it came back.
I am reluctant to have another flush as winter is almost over