BMW 535 heater temp probs

Hi all,

I've got an 1989 535i, with dual temp heater controls. Usually the passengers side works fine, but the drivers side usually pumps out hot air even when temp dial for driver is set to cold. Sometimes it works fine for a day or so, usually not.

I have found the two motorised heater valves under the bonnet (left side on firewall). Is it likely to be these -sticking / faulty . Everything else works fine-vents etc.

How do I test these ? Appears to have three wires going into them-I'm assuming a common, and one for passenger side and other for drivers.

Cheers,

Glynn

Is the controls for the HOT/COLD a cable actuated knob or is it electric ? You mentioned that the heater valaves are electric but are the controls themselves cable or electrical. The reason I ask is I had a gentleman witht he same problem on a ealry model Accord and it had the old style cable controls and even in the cold setting it was putting out warm air ( even when the A/C was on ). I found the problem to be a sticking temperature control knob. The knob on the front of the dash when turned all the way over the COLD wasn't all the way over because there was some slack in the cable. I tightened the cable and instant COLD and HOT temperatures from the vents.

If this is not what you had in mind please respond.

Thanks Jeff,

no cables, she's all electric. Everything -vent open/close, temp -the works.

I'd like to know what voltages (or how the valve is controled) I'm supposed to get at the water valves for the heater. I think that would direct me in the right direction.

I could always get a second have valve and swap it, but I really don't want to have to drain the water, dispose of it correctly (has antifreeze in it), muck around fitting the bits and then have to refill and get get rid of any air in the water system. All then to find out it may not have been the valves. Seems like a nightmare ready to happen!!!!

Any further thoughts ?

Glynn