Heat through middle A/C Vent

[talljames]

Hi all, need to bring this issue up again as I did not find a solution.

Started experiencing heat coming out of one of the center vents while air con on with three blue dots on the middle wheel. I wouls start the car and after driving in hot weather and then stopping and starting at lights etc., heat would come out of that one vent. All the others were cold. Moved the wheel to three reds dots and it was a lot hotter.

While having the problem i checked the temp of the exit hoses from the heat control valves (the two on the side wall) and one was hot and the other very hot.

Had the gas topped up and found it was low as it had not been done for some years.

Problem reoccurred. I turned the a/c off and had the vents set for external air into the cabin. three of the vents were luke warm but that particular middle vent was hot. Turned the air con on again with 3 blue dots and checked the electric fan and that was working fine.

When the air con is on and i have three blue dots is coolent meant to enter the cabin from the heater control valves?

Hope this is not a bad blending flap.

Any comments much appreciated.

[getty150]

Some of what you describe is acceptable...(If I read it correctly)
If the hot water control valve is not new or relatively new...id replace it!

Sent from my REVVL V+ 5G using Tapatalk

[talljames]

I am thinking that way but I need to confirm about the coolant path while 3 blue dots and air con on. Does anyone out there have a coolant path diagram showing all the parts involved for an E53 N62?

[X5chemist]

The center wheel (vents) are supposed to send cool or hot air regardless of temp settings right? The dots represent how much to blend hot or cold air.

[talljames]

Yes, that is right. My understanding is the heater control valves on BMW E53 X5 models controls the flow of hot coolant to the heater core but I am not sure if anything else control these valves. The wheel is supposed to affect the valves. From my test without air con it seems the heater control valves and the centre wheel decide how much hot air comes out of the vent with blended external air (if set to external). If the wheel is the only part then in my case with full on heat coming out of that one vent (with three blue dots) would suggest a faulty valve. The other unkown is do the left/right temp controls affect the air temp out of the vents without air con on.

[80stech]

AFAIK the dash vent control with the the blue/red dots has no control of the heater valves, just blend between what is selected and outside air. If you are getting heat anywhere with A/C selected there is a problem with the heater control valves, they are open (ON/Heat) by default.

[talljames]

oh ok, thanks. I must have misread then. So the heater control valves are controlled by electrical pulses which are determined by the left and right temp controls. Is that correct then? If that is the case and the air con is switched on by the snowflake button then no coolant should be flowing to provide heat out of the vents? This is why I wanted to see a diagram. I will check my bmw book. cheers

[talljames]

I better close this thread off. First time I have heard of vent temperature stratification. lol

https://www.bimmerfest.com/threads/e...-work.1350373/

I have ordered a new bosch heater control valve and will post up after it arrives and installed to let you know if it worked.


cheers