Leaking Heat

[ElNormo]

I've got a 1989 535i (about 210K miles) that is leaking heated air into the passenger cabin. With the air conditioning on, and all the dials toward "cold", I'm getting cold air through most of the vents, but am getting hot air from the small vents pointing toward the mirrors and through the foot vents.

Not just "uncooled" air... it's definitely "hot" air. If I turn the A/C off and just circulate outside air, same thing. It has been doing this occasionally since early summer.

If I turn off the blowers, I can still feel heated air leaking through the foot vents.

Someone recommend tapping the heater control valve with a hammer. I'm not exactly sure that the HCV does, and I don't really like taking a hammer to things I don't really understand. If someone can explain this a little more, I'd be willing to give it a shot.

Any ideas?

Thanks,

Norman

[Blitzkrieg Bob]

The heater control valves are solenoid actuated valves that close with the power on, thus they tend to get stuck in the open position.

I'd tray taking it apart and clean it rather than beating on it with a hammer..

If the rubber membranes on the valve pistons are rotted and leaking coolant back into the solenoid, you'll need to but a new one.

[ElNormo]

The heater control valves are solenoid actuated valves that close with the power on, thus they tend to get stuck in the open position.

If the valve was stuck open, wouldn't there be heat coming from all the vents?

Thanks!

Norman

[Blitzkrieg Bob]

If the valve was stuck open, wouldn't there be heat coming from all the vents?

Thanks!

Norman

Not always..depends on which set of vent flaps are open, and of course there are two valves controlling the two sides.