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Old 11-20-2004, 08:18 PM
AlexTheSeal's Avatar
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Join Date: Jun 2004
Location: Warren, OR
Posts: 248
Originally Posted by gsxr
OK - that's weird. You should not get any heat out the center vents ever, even with the #4 and #6 lines swapped. You WILL get some air out the center if you have the temp wheel in the middle and the system thinks it's too warm inside, but it should be cool air, not warm.
Are you sure about this, Dave? I've seen you say this before, and always took it on faith, since you're the acknowledged master of 124 ACC.

However, since I've got my '87's ACC into shape, I'm occasionally noticing warm air coming out the center vents under certain conditions. AFAIK the system is working correctly, except that I have blocked off the recirc small-lift line at the 7-port manifold---it doesn't hold vacuum and I'm not up for pulling the dash just yet---I'm waiting until the other ones go bad.

The situation I'm thinking of is this: I get into the car, engine cold, ambient temperature about 40 degrees. I start the car with the ACC set on "EC", fan on "AUTO", temp dial in the middle somewhere. (What do the markings on the dial mean, anyway? Is the temp you want the number at the middle of the exposed portion of the dial, the bottom, or the top? Anyway...) As the car warms up the system doesn't blow any air at all. When the coolant gets hot enough, it begins to blow a lot of warm air out the side and floor vents, and a little bit out the defrost vents. After about 15 minutes of driving, when the interior is warm, the ACC brain seems to shift into a distinctly different mode, in which it cycles between blowing warm air lightly out the side and floor vents, and blowing less-warm (but NOT outside temperature) air out the center and defrost vents.

Like I said, the system seems to be working fine... it certainly keeps a constant temperature in the cabin, and circulates the air very nicely so that I don't end up with roasted feet or eyeballs. But I've never had another 124 to compare this one to.

Please don't tell me this is another symptom of a head gasket leak!!!
AlexTheSeal: hack mechanic, inadvertent drifting champ, builder of infernal devices, professional epistemologist

'87 300D Turbo, roadtrip mileage champ (for sale!)
'92 Isuzu Trooper, mudder extraordinaire (for sale!)
'82 Honda Silverwing, cockroach of motorcycles
And various boring daily drivers...
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Old 11-20-2004, 10:05 PM
gsxr's Avatar
Join Date: Aug 2001
Location: USA
Posts: 7,989
Alex, per the owner's manual (and my personal observations) , you shouldn't get *heated* air out the vents. When the system decides it's warm enough inside and/or you lower the temp setting (cooler), it may let some lukewarm air out the center - not necessarily outside air temp, but still not hot/heated air. It's a complex system, that's for sure! I always assumed the desired temp setting was the number in the middle of the dial, but honestly I just move the dial to get the air temp I like and ignore the numbers most of the time!

And - lol - no, this should have nothing to do with the infamous OM603 head problem! There are enough of those already - just heard of yet another one this week on the MBZ email list.

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