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  #1  
Old 01-08-2003, 01:23 PM
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Join Date: Jul 2002
Location: KINGSPORT, TN
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Heater Is Just Warm, Not Hot

Can anyone tell me what my problem may be? I have an 89 300se and just had the brushes replaced in the blower motor due to it not blowing very hard. The armature looked good. The heater puts out more air now, but still does not put out enough. I don't see a difference when it is idling or when it is driven. Can anyone tell me what I might check next? Should I check the monovalve next? The air that comes out is warm, but not as warm as it should be. This is my first MB and I am used to the heater blowing hot if I need it and blowing hard if needed. This car just does not blow warm air as much as I would want. Any help would be appreciated.

Scott

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  #2  
Old 01-08-2003, 01:51 PM
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Join Date: Sep 2002
Location: Kingsport, TN
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Hi Scott,
I would try monovalve next as it will take only 10 minutes to undo the 4 screws and take it out. If the rubber diaphragm is broken, you need a new insert. Search under monovalve and you will find more detailed descriptions.
regards
Reinhard Kreutzer
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  #3  
Old 01-08-2003, 09:31 PM
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Make sure the thermostat is working properly. It's cheaper and easier to replace than the mono-valve. A good test for this is to restrict airflow to the radiator for a few minutes while idling, and see if the heat output increases. If it does, the thermostat is the cause. Make sure you watch the temperature guage.
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Old 01-20-2003, 10:27 AM
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heat blows warm

Over the weekend, I pulled the monovalve and checked it and I did not see any signs of cracks or tears. The part that sits down in the coolant did not look like it was torn, but was not perfectly circular in shape. I put back together and started the car with heat. It seems that the heat coming in the passenger floor is rather warm, almost hot and blows pretty good. On the driver's side, it is not as warm and does not blow as hard. Keep in mind I have had the brushes replaced and the armature checked out ok. I also checked the line behind the glove box and it seemed to me ok. Can anyone tell me what might be the problem? It just doesn't seem to blow as hard as it should. I did discover(MB is new to me) that the center vent slide bars pushed to the right cut out all cool air coming through the center vents. Maybe the small amount of heat blowing is the nature of the beast? If the thermostat was not working properly, would that cause the heat not to blow as hard or be as warm? Also, the temp gauge stays around 80-85 whether you are sitting still or moving. can you tell me where the thermostat is and maybe I can change that and see if it makes a difference? Got any pictures like those I have found on the monovalve? Thanks.
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Old 01-20-2003, 06:42 PM
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Hi SCOTTFISH,
this is where the monovalve breaks, it's the rubber between the mesh and the body. But if you have heat on the right but not as much on the left, could there be a gap in the ducting and the warm air blows out behind the instruments? Might have happened when the blower was installed? Just a thought.
Thermostat between 80 and 85 seems ok to me.
Good luck
Reinhard Kreutzer
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Heater Is Just Warm, Not Hot-cropped-monovalve-broken-rubber.jpg  

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