E30 M3 Heater only running cold

Hello fellas

Ive got a H plate M3, with a little problem.  On the weekend it was fine, but just now, the interior heater wasnt getting hot.  The car was warm and running fine, but the heater wouldnt get even slightly warm, annoying since it was fine on sunday.  I remember reading something about this ages ago.  I think something about a sensor or valve around the glovebox, that if knackered, will only let your heater run cold??

Help needed

Zain.

Jim,

Im sure Zains car had a new water pump recently. Zain, check the invoice set when you get home mate.

If i'm not mistaken, isn't this the heater control valve? There was a hands on fix in one of the Total BMW magazines of recent, but i cant locate what issue!!!

Anyone got an idea??

Here is the Total BMW quick fix....
Quick Fix PDF

Have you check the thermostat is opening correctly!

B1g Al wrote: there's a simple check to do. put your ignition on and turn of heater blowers, stereo and anything else that makes any noise. Now turn the hot/cold knob whilst listening with your ear close to the under side of glovebox. The hot / cold flap is operated by a small motor and if it is working properly you will hear motor move as you adjust hot / cold knob. If this is working then you know there is a problem with water circulation.

are you sure that works for a LHD E30?

I have to differ with some of these posts, and I think I might have your answer. You are correct in that the heater valve is on the left on an LHD E30, and that there is some noise when it moves open and shut. 

However, the post about the motored flap is entirely correct (for my car anyway).  There is an air flap, the mechanism for which is located on the right hand side of the front of the heater box, pretty much directly the backside of the fan blower switch.  This si motored open and shut, controlled by electronics in the heater control unit (backside of the blue/red control knob).

If the motoring fails on this flap, is stays in one position, and the failsafe is cold.  You will have hot water circulating through the heater matrix just fine, but no air blowing over it.

To check this, open and drop the glovebox.  Remove the filler panel between the dash and the glovebox opening (a screw by the glovebox latch, and pinned by the plastic twist screw which holds the extreme front RHS of the central console.  You then see a linkage pretty much horizontal on the side of the heater box.  Press this off the motor end (behind the fan blower switch) and it becomes floppy.  With the engine running, pull this linkage towards the back of the car.  This moves the air flap, and if the heater control is set to warm (ie heater water valve already open) I reckon you'll have warm air.

If it is the motor, I have a spare.  If it is the heater control  I don't, and they are something like £300 plus to replace.  If it turns out to be the control, I would bypass this flpa, and just have it permanently in the warm position.  The heater will then work on hot or cold, but controled only by water flow - in other words it won't cool down the airflow so quickly when you turn the heater off.  Better than spending a wad though.

Let me know if this is the problem, as I'd love to know I wasn't the only one! 

I had the same problem with mine. it would work fine and then just go cold. a few weeks later it would work fine again. It ended up being the temp control unit. It is a semi climate control and being it is electronic you won't hear any flaps. I replaced mine and worked fine after that. It was about £200 though.

Usually you can identify them by the degree numbers printed around the heater control (on the red/blue ring)

Edited by UweM3

ian332isport wrote: SFH3L wrote: I have a perfectly good one for sale or swapsies? What sort of money are you looking at for the motor ? I've just installed aircon, and it would be nice if I can convert to full climate control Ian.

Ian, I really admire you patience and workman skills!
As much as I would like an aircon, I just wouldn't want to take the whole dash out etc, etc. I rather put an engine together.