Hi All. I've a 1999 S500 and am totally perplexed with a problem that's recently cropped up. With the A/C on, aiflow from the driver facing front vents will suddenly stop and all airflow gets redirected through the defroster vents. It happens with the vent controls in auto and manual. It comes and goes of its own accord. On humid days, you're suddenly fogging up the windshield. Any input would be greatly appreciated. Thanks!

CR

 

my 1991 350sd does similar thing-seems to be related to the vacuum systemalways have cold air coming out of the two most outer ventsbut not in the two front [inner]vents .
the defrost works okcould it be related to the ambient temperature??

I'll be looking for any suggestions here.
thanks


barnes

1991 350sd
1987 300dturbo
1979 300d
several mg-"b's"
jaguar mark 7
mercedes 220s
jaguar xk140mc
mg-td

 

It's definitely a vacuum issue. Look for any loose hoses underneath the hood. It's probably a quick fix. Your looking for hoses with about a 1/4'' diameter, not the large hoses. Start from the air filter and work your way around.

 

I think that the 1999 S500 might have an alternator issue. It's not maintaining the proper charging level to keep the A/C running properly. It can happen intermittenly or after driving a long distance. If you turn on the A/C and let it idle and it doesn't maintain the proper cooling temoerature, it's probabaly the alternator.

 

Hello, I have the same similar problem as Creyesjr thread (below) on my 1999 S500. But my problem is in the center vent as oppose to the driver side. Any suggestion is greatly appreciated.

Thanks
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Hi All. I've a 1999 S500 and am totally perplexed with a problem that's recently cropped up. With the A/C on, aiflow from the driver facing front vents will suddenly stop and all airflow gets redirected through the defroster vents. It happens with the vent controls in auto and manual. It comes and goes of its own accord. On humid days, you're suddenly fogging up the windshield. Any input would be greatly appreciated. Thanks!