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  #1  
Old 01-11-2005, 02:30 AM
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Thumbs up HVAC - only blows hot?

Any initial clues or is my climate control unit need replacment?

Even on vent it's still hot and it's ~40°F at night...

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  #2  
Old 01-11-2005, 08:23 AM
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If the monovalve coil does not energize due to failure of coil, connection, CCU or attached wiring, then the valve remains OPEN to allow hot coolant to flow through the heater core. Nice that MB designed it to usually fail in this mode rather than no heat. Check your monovalve for operation with a pair of test leads. You can easily hear and feel the movement inside (engine off, of course)
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Old 01-11-2005, 08:24 AM
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Not necessarily - guess as people we always think the most expensive part broke. Use the DIY tab at the top of screen and look at the ACC diagnosis.

If you do find that you need the CCU I have one that was part of a batch purchace, part #136-830-02-85
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  #4  
Old 01-11-2005, 01:30 PM
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Thumbs up

Can it really be that simple!? I'll have to look at mine tonight!
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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
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  #5  
Old 01-11-2005, 01:45 PM
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300sd blows hot

Try changing the auxillary water pump which assists in the climate control. I had the same thing happen and when I changed the aux water pump it started working fine. it may not be your climate control module. Good luck it is very easy to replace the Aux Water Pump it is near the battery along the fire wall. It has coolant lines running into it and should release with 4 screws and one electrical plug on the top.
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Old 01-11-2005, 02:31 PM
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you are describing the monovalve, not aux water pump. The Aux water pump only functions to help circulate warm coolant at ldle. It is an SOB to replace
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Old 01-11-2005, 02:41 PM
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Quote:
Originally Posted by meltedpanda
you are describing the monovalve, not aux water pump. The Aux water pump only functions to help circulate warm coolant at ldle. It is an SOB to replace
the monovalve is basically a valve operated by a big solenoid. the aux water pump is, well, an electric motor powered pump. It helps out a lot at idle, but I think it runs at other times too. IMHO neither unit is difficult to replace as long as you take them out together. See my other recent post about this unit - let me know if I'm missing anything in the description.

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