BMW Forums : BimmerForums banner
1 - 15 of 15 Posts

·
Registered
Joined
·
49 Posts
Discussion Starter · #1 ·
Over the Christmas break I have for obvious reasons had my heater set to hot (non-air con model so just heat from the engine). However when I then tried to change the temperature back to cold (or cooler) it remained hot, and when I say hot, it's the hottest setting, and the temperature doesn't change in relation to the temperature control position, unless of course you have it through the centre vent as this only ever blows cold air... and still does suprisingly...??

I am under the impression that it provides the different temperatures just by adjusting a 'mix-valve' with hot air and cold air (engine & outside), maybe this has become stuck? However if it is stuck, how can it still blow cold air through the centre vent?? It there a thermostat that has broken and somehow the centre vent selection bypasses the heater control all together??

It isn't too much of a problem at the moment as I can tilt the sunroof open to counter-act the hot (rather than warm) window heater... however when summer arrives it's nice to be able to cool the car down without having air blasted directly in your face!

Any help/suggestions are much apreciated!
 

·
Registered
Joined
·
564 Posts
Could be your temperature control valve mate that is located near your fuse box just under the p/s wiper arm in the engine bay, check the wiring around it to see if it has split or any obvious signs of anything untoward.It could also be your inhibitor for your heat control but I doubt that it would be down to this to be honest.On your centre vent mate can you twist the open close knob and just check to see if you have one where you can either have hot all the time or cold all the time.... some models do have these kind of centre vents as I have one myself, if you have one then you will have blue dots/dashes and red dots/dashes if you have it on the red dots then it is constant heat but if on blue it is constant cold. just something for you to look at mate
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #4 ·
There are no coloured dots on the centre vent open/close wheel... but there's a blue line on the 'zone' select dial for the face vents and it only blows cold. It's not got air-con though? If that makes a difference. I found out similar info with regards to the temperature valve from an old thread on the US bimmerforums... I'm going to have a look at the weekend when there's some light to see what's going on. If I get stuck I'll give you a message and maybe you can help me out! Cheers.
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #6 ·
Cheers Ronnie, I'll try that at the weekend if there are no suspect wires/connections. I've seen that heater diagram so many times in related posts!! Unfortunately I don't think it's a problem with that part... as it still blows cold from those vents... which is making me think (if the control voltage signal for the temp dial and the cold override from the 'zone' select dial go to the same connector/pins) that it could be a problem with the dial interface rather than the valve itself? Otherwise would it not also blow hot through the centre vents if the valve is stuck open?

And you've just confirmed for me that the replacement part I was looking at is the right one! Cheers!
 

·
Registered
Joined
·
564 Posts
There are no coloured dots on the centre vent open/close wheel... but there's a blue line on the 'zone' select dial for the face vents and it only blows cold. It's not got air-con though? If that makes a difference. I found out similar info with regards to the temperature valve from an old thread on the US bimmerforums... I'm going to have a look at the weekend when there's some light to see what's going on. If I get stuck I'll give you a message and maybe you can help me out! Cheers.
No worries mate! give us a shout if you want, I can bring my diagnostic kit to play with!
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #9 ·
Right, I've tested the voltage from the control dial and it seems to only change between 5.5v (ish) to 13.5v (ish), and changes between the two somewhere in the middle of the hot/cold range on the dial. It seems to have lost an intermediate 'warm' voltage to send to the valve.

Having found this out I've left the blower on for a while (so the ducts cool down) and it does blow cold if it's on the coldest setting... Does anyone know if there are supposed to be intermediate voltages, or does something else control the hot/cold mix?

Thanks guys!
 

·
Registered
Joined
·
20,393 Posts
If you have the dials shown in the picture above then the centre vents will blow cold as it was how they were designed.

As for the other vents do they blow hot or cold depending on what temperature you have selected?
 

·
Registered
Joined
·
49 Posts
Discussion Starter · #11 ·
Centre vents always blow cold. The foot/window vents blow hot OR cold, but no longer have the intermediate setting for 'warm' which is what I most use when commuting. I thought there must be a variable resistor involved to create the changing voltage... but I don't know where it might be located behind the dash. It could just be that this has failed and needs replacing...?
 

·
Registered
Joined
·
20,393 Posts
Centre vents always blow cold. The foot/window vents blow hot OR cold, but no longer have the intermediate setting for 'warm' which is what I most use when commuting. I thought there must be a variable resistor involved to create the changing voltage... but I don't know where it might be located behind the dash. It could just be that this has failed and needs replacing...?
IIRC it's built in with the control panel, I think NealP will know this for sure so will bring the thread to his attention :thumbsup
 

·
Registered
Joined
·
11 Posts
Ok Ron, I had a look at the schematics for this model and this is what the control panel looks like from the inside. The only variable resistors that are of importance are the rotary temperature switches linked to the air flow and temperature valves.
 

·
Registered
Joined
·
116 Posts
Sorry to resurrect a thread but did you get this sorted?
I'm having the same problem with only HOT air from the windscreen vents. Have changed the HCV but it didn't resolve it.
Very interested to see what you did if you got this fixed....
 
1 - 15 of 15 Posts
Top