Ok, I've asked this before, but it was quite a while ago and I don't remember the answer.

Actually it could have been last week and I wouldn't remember...

Anyway, my car is a 1982 242 turbo, pretty much factory stock. I have noticed that when I have the defroster on (button in) and the heater off (button out), under normal steady-state driving, the defroster works fine. However, under acceleration (ie, the turbo has pressurized the intake), air blows out the heater vents and not out the defroster.

I seem to recall that there's a little vacuum valve in the system that's probably the problem, but I don't remember how to isolate it and where it's located...?

As always, thanks.

You'll find a little plastic device in line with the small black vacuum line that feeds the climate control vacuum reservoir. The reservoir is in the dash, under the heater core, but the hose to it enters the right side of the firewall through a black plastic grommet.
Follow that to it's connection on the intake manifold, and it may hook to a group of other larger vacuum lines. Either way, you'll come to the check valve in that hose.
That's what needs to be replaced. The unit with the same function from a later 740T would probably work fine as well. Also note that a couple people have mentioned cleaning these with PB Blaster- your results may vary.

Good luck!
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Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '89 244DL/AW70- 212K Not too distant past: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K

I cleaned mine by running hot water through it under the tap. I blew through it in the "stop flow" direction beforehand - it leaked slightly. Afterwards - air tight.

I prefer to use the least volatile substance necessary to clean something, figuring it's less likely to damage it in any way. It's held for at least a year.

Check out the "240 vent wierdness" link on my pages, this is a common problem with both turbo and non turbo 200s.
Cheers
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Dave Shannon
Spring Valley, California
'84-245T 190K+
'88-240 190K+
'65 1800S ????K
'73 1800ES 117K
'92 745Ti 150K
Jeep Wrangler Sahara 10K
my pages