Car is '96 S500 Coupe (140). No garage available, so it sleeps outside... temps have been really cold lately (could use some of the Global Warming right now)
Anyway, when overnight temps drop below about 30 degrees F, there is no heat to the floor ducts in the morning regardless of what I select on the climate control. All I get is warm defrost. I can switch to dash vents, but still no floor heat.
After driving for about an hour or so, something moves and all works normally after that...
I assume there is a flapper/damper in the heat box that controls flow to floor duct that binds with extreme cold. Once the car starts to warm up a bit, it moves. (yes?)
This will only get worse with time, so would like to fix.
Anyone know where this flapper is? I can't dive into this problem until weather warms a bit, and of course, it will work fine when I get there.
Ideas?
Thanks, KenP

How soon after the car reaches "normal" operating temp does the heat come out?

Well, that varies with outside temp and whether or not I stop on the way. Let me explain...
I commute two hours to work. Heat starts coming out of the defrost vents and side dash vents within about 8-10 minutes of leaving home. If its cold (in the teens), and I don't stop for gas, it takes about an hour before the floor vents start delivering heat to my feet. When it happens, I can hear the defrost air volume drop off and the heat begins in the floor area in a matter of 4-5 seconds... just as if a flapper/actuator moved.
Before that, it almost feels like cold air is being sent to the floor.
Engine warms to about 80 degrees C within 15 minutes of home, so its not an engine temp issue.
If I stop for gas along the way (let the car sit for 10 minutes with a semi-warm interior, heat will begin to come from the floor ducts when I start up again. I think this is because the air box gets warm.
Anyway, if I start off and its 30 degrees F or higher, everything works fine.

Strange, eh? Ideas?
KenP

Sounds like water vapor freezing out in one of the vac lines or servos, so that the flap won't move until it thaws.

Check the vac lines to the climate control -- if you have a leak, you have low vac (and will only get defrost until the vac comes up). Also, this is an electronic unit -- it may be malfunctioning.

Also, you should get heat in a couple of minutes -- as soon as the temp gauge gets up to 50 C or so.

Peter

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