Hello all- New owner here of a great '90 300TD and I absolutely love the car and am constantly amazed at the quality. One small glitch I just noticed (now that the temps are up and the A/C is on) is the central air diffuser doesn't work. Manual control is open, side vents, lower vents, and windscreen vents all pump cold, but that center one would certainly increase efficiency. Any ideas that don't include tearing apart the dash, which would have to be a PIA project?
Vehicle: 1993 400E 222111 miles "Gunter", 1999 ML320 187000 miles "Fizgig"
Location: Silverdale, Wa
Posts: 729
Center dash vent
Find the vacuum manifold (underneath dash passenger side behind glovebox) put vacuum to each line and see if a stronger vacuum will open center vent. If so its a CCU (climate control unit issue) If not the rubber diaphram in the pod is toast and must be replaced, meaning dash has got to come out.
Air does not always come from the center vents when the a/c is on. The difference between set temp and interior temp must reach a certain value before the system goes to max cool mode.
If you turn the set temp way, way down the center vent should blow cold air.
Jayare;
Thank you for the welcome. There is an amazing amount of good info and knowledge here. Unfortunately, nothing from the center vents at any setting or mode. This doesn't bode well, does it?
Hello Augapfel- I think we had the temp differential yesterday. (90+ F !) I'm not exactly in panic mode yet, as the cabin will cool down, eventually. Just seems that the system has to work pretty hard to do so.
Your car would have had an R-12 system originally. Is it still R-12 or has it been converted to R-134a? A converted car will not cool as well as one still running on R-12. Still, that will not affect WHERE the air comes out.
It sounds like you may need to replace one of the vacuum actuators. I haven't done the center outlet one yet. So far only the defroster one quit on my 260 and that one is easily accesible once you pull the glove box insert. I know that some of the actuators are a REAL bear to get at. Hopefully the one on yours is not.
Must be that clean living paying off with dividends! Pretty much resolved myself to the task of tearing out the dash to replace the actuators. While driving down the highway in 95+ heat, the car suddenly started cooling down quite nicely-the center vents started working!!!!! And have been going ever since. (couple weeks now) Gotta love that car!
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