Passenger heat control not working

[Anton CH.]

Ever since I bought the car the control for the passenger heat never worked. Still blows warm air but only when the driver heat is turned to hot. What are some common things that break and I should check out?

[Paul in NZ]

its probably the heater valves sometimes they will respond to a few sharp taps with a lfh(as opposed to a bfh!)

[ryan roopnarine]

"rebuild" them, as it working on one side and not the other generally seems to be that one is a little stuck (down with crap) than the other.....a good heatervalve clean procedure is available on the e32 register.

[ryan roopnarine]

the main thing you're trying to do is polish the metal sliding surfaces with brasso or such to get them to move more effectively.

[Anton CH.]

Paul, what is lfh or bfh?
Ryan, can you please provide a link to the e32 registry.

Could it maybe be the switch(thats what I was thinking before)?

[ryan roopnarine]

http://www.users.qwest.net/~gbower/b...eatervalve.htm

and i sincerely doubt its the switch, the differntial in temp is due to one of the two solenoids doing something weird.

Paul, what is lfh or bfh?



Ryan, can you please provide a link to the e32 registry.

Could it maybe be the switch(thats what I was thinking before)?

[Brian C.]

BFH........Big Friggin' Hammer
and, obviously a Kiwi derivation of the same,
LFH........Little Friggin' Hammer

Isn't it great how we all speak the same language all over the world. "If it's broke......smack it once or twice and see what happens!" I feel so much closer!

Brian C.

[Anton CH.]

Do you guys know how the valve works electrically? I hooked up a voltmeter to the input terminal (3 wires). I am assuming middle is ground, moving the drivers heat changes the voltage on each terminal from either 12.2v or 0v. Passenger heat has no effect on voltage. Is there something electrically wrong? I would imagine that the voltage would at least decrease gradually rather than 12 or 0 volts.

[ryan roopnarine]

is that it operates on voltage pulses, so measuring it per se might not work...i'd hit the valve and see if anything changes first.

[Anton CH.]

Found this on roadfly for anyone who is having similar problems:

"When the heater blows hot / cold and not warm, it's likely the plungers in the heater control valve are sticking. Here's how you can check:

1) Get car warm in side...normal temp.
2) Get a 12volt bulb tester
3) Pull the harness plug from the heater control valve.
4) There are 3 wires, one for the drivers side, one for the passenger and one for the ground.
5) Using the bulb sensor, test each lead. Have the both temps sent to about 72 degrees. The bulb sensor should slow flash on and off at around a 1-2 second pulse.
6) Change the temp to hotter, the pulse rate of the lights should increase/decrease (can't remember which).
7) Check both sides.

If both side pulse AND the rate adjusts as you change the dial setting, it's highly likely the control valve is bad. The pulsing signal indicates the brain unit is functioning correctly. If the lights don't pulse at all; then it's likely the HVAC unit it bad or something else is wrong.

I have followed this board for 3 years and have yet to see anyone replace the HVAC brain; it's almost always the heater control valve.

Water gets into the solenoids when the plunger seal fails and the unit stops working or works intermittantly leading to strange heating behavior.

Try this simple check before you do something more radical!

Cheers!

Jeff
90 535i w/new heater control valve
"
I tapped them with a screwdriver, going to see if it helped, otherwise going to "rebuild" it.