hello all
My 1987 300sdl blows only HOT air out of the vents and to date I have had everything having anything to do with the a/c under the hood replaced. Still no cold air. My indy is very perplexed and he now wants to look under the dash. I was wondering if there are any recomendations as to what the problem could be. The buttons on the dash have no direct effect on the circulation of air as all the buttons seem to direct the air out of the same vents. HELP I live in deep south texas and I need to carry around a change of shirts to go to work as I am drenched by the time I get there. Any recomendations are greatly appreciated.

Sounds like a bad monovalve diaphragm.

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Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

thanks for the info, would that cause only hot air to vent out. Is there something I can do to repair it myself?

forgot to mention that cold air does blow out of vents when first started however once engine warms up air in vent warms up to really hot. is air somehow being drawn from the heater core?

Do a search on monovalves. I believe you will find all the information you could want.

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Mike

2000 SL500 22,000 miles
1981 300CD 188,000 miles
1979 450 SEL 266,000 miles
2005 Cadillac CTS 25,000 miles

I replaced my monovalve, and it solved the problem for about a month.

Now it still only blows hot air once it's warmed up.

Could the replacement monovalve have been bad? Is there any way if I pull it out to test it or lube it?

Thanks!

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Aaron
'84 300D 267,000 - Running WVO - Rice Bran Oil - Mmmmmm, fishy...
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sounds like the members (self included) that hang out in the basement(open discussion) when our cars are not broken .there's more than enough hot air in the dank basement to heat the rest of the forum.............

William Rogers..........

off to the cellar