My heater is not right - PeachParts Mercedes-Benz Forum

#1 02-08-2002, 01:54 PM

My heater works sort of. As long as I leave the fan on low I get heat out of my heater where it is supposed to be, but when I turn fan on high by the swich or by turning on the deforster it gets cold in about 15 seconds. After doing a search I keep seeing the mono valve being a problem with heat. Can that cause the problem I am having? The problem is on my '91 300SE.

Thanks,
Davis

sixto · #2 02-08-2002, 03:03 PM

A bad monovalve will provide some heat at low engine speed and little to no heat at high engine speed. It takes a few minutes to check your monovalve so it's hardly worth speculating.

Do a search on monovalve and username sixto. Also check out http://photos.yahoo.com/tabijan. One of the albums has photos of how to get to the monovalve.

Sixto
91 300SE
81 300SD

#3 02-12-2002, 10:32 PM

Quote:

Originally posted by sixto
A bad monovalve will provide some heat at low engine speed and little to no heat at high engine speed. It takes a few minutes to check your monovalve so it's hardly worth speculating.

Do a search on monovalve and username sixto. Also check out http://photos.yahoo.com/tabijan. One of the albums has photos of how to get to the monovalve.

Sixto
91 300SE
81 300SD

I have the same problem and just got my car back today after spending a total of 500.00 to get it fixed and still there is no heat when I hit the higher speeds. I went to the link in the above post but it doesn't work....Can you or would you mind elaborating a little more on the monovalve thing.....I would appritaite it. :-/

80-240D
86-190E (cold)
65 Bonniville convertible

riske · #4 02-12-2002, 11:09 PM

Davis,
The heater on my 82 300SD has the same symptoms as you describe. I changed the mono valve but that didn't solve the problem. I just keep the fan speed on low and the interior heats up fine, it just takes longer.
If you get yours fixed, let me know what the solution is.
Thanks...
Bill

#5 02-13-2002, 12:32 AM

Well thanks Bill, I started to order the part on line and didn't get checked out because I got called off to work. You just saved me a few bucks. I think it is something to do with air damns/baffles opening when the fan gets turned to high and letting outside (cold) air in, but I don't know enough about them to figure it out. At least I live in Texas and it doesn't get real cold, but when I turn on the defosters it gets cold also.

sixto · #6 02-13-2002, 12:32 PM

Quote:

Originally posted by Indianadriver

I went to the link in the above post but it doesn't work [/B]

The period at the end of the URL shouldn't be part of the URL. Try http://photos.yahoo.com/tabijan and go to the Monovalve album.

My monovalve had an obvious tear.

Sixto
91 300SE
81 300SD

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