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Microstar · Joined: 23 Jan 2002 Posts: 2 Location: UK

Car is E32 1992 730i (although I think E34 has similar arrangement).

My problem is that the battery goes flat overnight.
After some detective work I discovered that (with ignition *off*)
"something" is drawing 2A of current.

I found that the heater valve is making a regular 'pulsing' noise.
Pulling Fuse No.20 stops the noise and the current draw drops by a
factor of 10.

It seems to me that even with the ignition off, the heater controller is
driving the water valve.

I only just got this car and don't have any technical data. Can anyone
help me out with the following:

1. Would the Haynes E34 5-series manual be relevant to the heater
components on my E32?

2. How is the water valve operated? Is it just ON/OFF (power/no power)
or is it pulsed in some way to give varying amounts of opening?

3. How do I remove the heater control panel and ECU etc.?

4. Last but not least - anyone had this fault before or can anyone give
me hot tips on a possible solution.

Thanks,

Eric

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Please remove 'NOSPAM' when replying

PJK

I think the heater control sends current to the valve to shut off the coolant flow. At least that is how it works in an e36. By the way the valve assembly has two valves and the heater core has two sections, one for the passenger and one for the driver.

I think the valves are cycled on and off to control heater core temperature, as opposed to some pulse width modulation scheme to attempt linear control of the coolant flow.

The Bentley manual has reasonable wiring diagrams, but is not very good for component location.

Removing the heater control panel is a challenge. It involves removing the cap from a button and inserting a small screwdriver thru a hole to release a plastic latch. Check the Bentley book. I had to remove the panel to replace some light bulbs. I broke the latch. The BMW service manager told me that out of 20 that he hs done so far he broke most of them.
No big thing, there is enough friction to hold the panel in without the latch and it will be easier next time.

Good luck,

Phil

[This message has been edited by PJK (edited 01-25-2002).]

flyer72 · Joined: 25 Jan 2002 Posts: 1 Location: Palo Alto, CA USA

Had a 730AI from 92 which had a dead battery a couple of times - never really thought too much about it. Lately the problem became very bad - had a specialty company into car electrics look into it - found out that the carphone installation (unused since several years) was the culprit. BMW dealers had no clue and replaced the battery 3 times!