Heater Won't Switch from Defrost to Floor - Mercedes-Benz Forum

 
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post #1 of 6 (permalink) Old 02-13-2010, 12:03 PM Thread Starter
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Heater Won't Switch from Defrost to Floor

I have an 85 300DT and while the defroster on the car works fine (I just changed the blower/motor), I have never been able to use the console switches to change from defrost setting to the floor. Regardless of the switch I choose, it remains fixedly on defrost setting.

Is there an easy fix for this so we don't have to drive with frozen toes?

Last edited by danashields; 02-13-2010 at 12:12 PM. Reason: clarification
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post #2 of 6 (permalink) Old 02-13-2010, 01:27 PM
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Sounds like your vacuum controls are not operating and the system defaults to defrost.
The vacuum connectors in the oil filter area are the most common problem.
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post #3 of 6 (permalink) Old 02-13-2010, 02:15 PM Thread Starter
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Heater Stuck on Defrost

I take it that since I combed through the vacuum lines around the filter and that they all look good, the same could hold true for any lines that go through the firewall, correct?

If so, I'll remove the under dash panel tomorrow to give it a look-see.
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post #4 of 6 (permalink) Old 02-13-2010, 03:20 PM
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Go to W123 section for more info how to deal with those pesky vacuum lines.
At some age they cost lot of troubles. Is you engine shutting off OK?
I wouldn't rush into opening the dashboard before double checking the easy stuff.
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post #5 of 6 (permalink) Old 02-14-2010, 05:05 AM Thread Starter
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Vacuum Lines

Engine shuts off fine. But vacuum lines don't work for door locks either. I was under the panel a couple of years ago to install something, so it's possible that it was I who was the bonehead who jarred something loose under the dash.

I will take some time to look under the W123 topic. I didn't see a page devoted to W123 on the forum's main menu, but I'll keep hunting around. (Hopefully I won't jar anything loose in my quest to find it.)

Last edited by danashields; 02-14-2010 at 05:05 AM. Reason: clarify
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post #6 of 6 (permalink) Old 02-14-2010, 09:41 AM
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Look in the sedans section for W123. If your locks aren't working that might point to the PSE pump. Locate that and check the tubes coming from it.

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