I have a 1987 SDL. Great car, a/c blows "cool" and heat works fine. However it seems to be stuck in defrost. Even set on regular heat/air conditioning settings, the air will not blow out of the front center vents. It confuses me because it will blow out of the rear vent the side vents and just stay blowing out of the defrost vent on all settings.

If anyone has had this happen to them or might know how to fix it please let me know.

Welcome to Mercedesshop!
Can I assume you have checked fuse #5? Also do a search on the forum "Mono Valve"
Vent issues are usually associated with "vacuum pods"

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i switched out the fuse #5 and it was to no avail, i need a little more help with the two other approaches. Im knew to this and have only had the car a month where do i start looking next?

Thanks

hi,

i'm having the same problem with my '90 350sdl. what i've figured out is that the A/C keeps coming out of the defroster unitl it goes out of recirculate mode. the A/C is set tostart in recirculate for 20 minutes or so....read it somewhere. once it goes to fresh air, it switches to dash vents. tested it today, and as soon as i manually turn on recirculate, it switches to defrost, turn off recirculate and it switches to dash as it should. i was stumoed for awhile, becaue it only does this when it's over about 80 degrees. so what i've figured out is that it goes to defrost whenerver it warmer (which means A/C is starting in recrirculate mode. so, the answer seems to be the defroster "pod" which i think is easilyaccessible if you pull out the glovebox. let me know what you figure out.

peter

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"Murray" 1990 350SDL 89,000

defrost is the default setting if there is something wrong, on my sl the vaccum pod that controled the defrost flap had a bad diaphram in it, parts cost $5, labor was $200, had to remove steering wheel and instrument cluster to get to it.