Re: HVAC Problem (archive)

I have a '85 735i and after using the heater and then turning it off I still get hot air comming out if the defrost vents eventhough everything is turned off.

Does green light above selected pushbutton stay on when volume thumbwheel is on 0? Most likely a microswitch on the thumbwheel board. Easy fix, my blower never shuts off either, haven't bothered with it.

If I go to use the A/C then I get A/C comming out the defrost vents. Turn that off and still get air comming out the defrost vents. This air only comes out when i'm moving. I assume that something isn't closing and therefor a vaccum leak but where should I be looking first.

Search archives, I know I've posted on this a couple of times. Take the cowl off and make sure the vacuum resorvoir and tee fitting (passenger side under cowl) are not leaking. Then, block the vacuum to *both* fresh air actuators under the cowl and try the system. These places are most notorious for vacuum leaks - assuming of course you've already checked the integrity of the vacuum line from the vac pump/intake manifold/check valve to the resorvoir. I have the vacuum line to the driver's side fresh air actuator (again, under the cowl, easily accessable from the engine bay) plugged - this is a two-way diaphragm, it's hosed, and I only got cold air out the defrost vents with it as it leaked. If your system has ever been worked on it is possible some of the vac lines have gotten knocked off ... yuck ..

I've been to a BMW dealership but those guys don't know their ass from a hole in the ground.

I should copy/scan the HVAC troubleshooting pages from my BMW manuals if someone would post them somehow ... they have step-by-step troubleshooting, very very very very very helpful.

Your help would be appreciated

HTH -

Follow Ups:

[ Follow Ups ] [ 7-series (E23) Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.