1995 540i heater valve problems

[Clarksonvalley]

I get the smell of something electrical overheating when the car is running - coming from the vicinity of the heater control valve and aux. heater pump. The cooling system is full of 50/50 antifreeze and has been fully bleed. I replaced the aux. heater pump thinking the motor was going bad, but the same smell still exists with the new pump. The aux. heater pump is getting 12.5 volts with the ignition on - this pump runs all the time the ignition is on and all the time the engine is running regardless of where the driver and passenger rotary heat control switches are set - this agrees with the heating system wiring diagrams. I get 12.5 volts at the heater control valve, but the voltage stays the same regardless of where the rotary heat control switch is set - this does not seem correct as the voltage should vary with the rotary switch position in order to open or close the heater control valve. Only when the driver rotary switch is fully rotated clockwise does the voltage to the heater control valve go to zero. Anyone had the same experience or have a solution?

Tom

[shogun]

the aux water pump does not run always, it starts only when heater is on and the coolant is above 30 degree Celsius and when heat is needed depending on the settings on the thumbwheels on the control panel.
It pumps 950 l/h. Here is a 53 pages tech info in German language how the system works
http://www.e38.org/e32/klimaautomatik.pdf
even if you do not understand, you can read the drawings, aux water pump control is in section 5.8

Maybe the control panel/module is defective.
IHKA pinout
http://www.bimmerboard.com/forums/posts/426626/
heater valve pinout
http://www.bimmerboard.com/forums/posts/841827/
wiring diagrams
E34 (1988 to 1995 5 Series) Wiring Diagrams

[Clarksonvalley]

As I look at the wiring diagrams, the aux. water pump relay coil gets power from fuse F29 which is' hot in run and start' and the water pump relay power contact gets power from fuse F9 which is 'hot at all times', so the aux. water pump appears to run at all times. This would make sense as the cabin temperature is regulated during the air conditioning mode by adding heat to the cooled airstream via the driver and passenger heater rotary switches. Wish you had an English version of http://www.e38.org/e32/klimaautomatik.pdf.

Do the water control valves position themselves in response to a variable voltage from the rotary switches (do they actually vary the voltage as the switch is rotated) or do they oscilate between 100% open and 100% closed in a frequency to vary the water flow? And, where do you think I am getting the 'pending electrical fire smell' from - the aux. pump or and water control valves?

Tom

[shogun]

copy or retype the description of the aux water valve and put it into google translate. It clearly says that it only runs when heater is on and from a certain coolant temp., and that makes sense, because first the large coolant cyle is closed to heat up the engine, and only when engine operating temperature is reached, the large cooling cycle opens by thermostat opening and then the hot coolant comes to the heater valves. Small cooling cycle means engine only.
water control valves position themselves by variation of the voltage at thumbwheel, actually they pulse. Depedent on the temp adjusted and the water flow and temp sensors feedback, controlled by the IHKA control unit

[Clarksonvalley]

Yes, I thought of the Google translate - can't copy from a PDF and paste onto Google translate, so I'll do it the long way as you suggest and retype. Any thoughts to the source of the burning electrical smell I am getting from the underhood area around the aux. water pump and the heater control valve? Is there any way to use a volt meter to check for the proper signal from the driver and passenger rotary switches to the heater control valves? I get a constant 12.5 volts on the driver rotary switch until you rotate it all the way clockwise and then no voltage at that point. I get no voltage regardless where the passenger rotary switch is positioned with the driver rotary switch past its detent?

Tom

[Clarksonvalley]

Shogun - and thoughts on my last reply?

[632 Regal]

Tom, your passenger thumb wheel is fubar which is why you get no action. However the driver side should control both sides for the most part. Are any wires getting hot near the aux pump?

[Clarksonvalley]

Thanks for your reply. I've been away from the BMW problem rebuilding my wife's Miata engine. As I remember, I get 12 volts at the pump and nothing at the water valve. I understand the water valave gets a pulse voltage from the dash rotary switch, but I don't see anything. I'm going to try running just the aux. water pump and see if I smell the nasty electrical smell - it's a new pump. If that's OK, I connect the water valve and see if the smell appears. I may order a new water valve if the smell appears. If the pump and water valve are OK, I'd guess the problem is with the rotary heat switches in the passenger compartment. The rotary switch does not sound like an easy fix.

Tom

[shogun]

sorry, was on overseas trip and could not reply. Use a small spare bulb from brake light or so and solder to short wires on it with a crocodile clamp and then test the function of the thumbwheel.
Do not put the thumwheel on full heat over the small resistance, because then the heater valves do not get any power. Use the bulb on the heater valves and then turn the thumbwheel slowly up and down, then you should see the bulb pulsating. That is almost impossible to see with a digital voltmeter.
You can disassemble the rotary switch and test it, here is some info how to disassemble it

BMW E32 Climate Control Illumination
In the worst you can also buy a used control unit from the Bay, usually not very expensive.

But if you nasty electric smell, then it could mean that maybe some wires are shorted/blank somewhere.

[Clarksonvalley]

Shogun,

My 540i E34 does not have thumbwheels - it has rotary dial switches, one for the drivers side and one for the passenger side. As I understand the test with the light bulb, I would connect it in series with the water valve solenoids, not in parallel - correct? I'll also check for wiring shorts to ground - can't believe there will be any shorts or the whole thing would have burned down by now or at least blown a fuse.

Tom