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  #16  
Old 01-07-2007, 05:30 AM
toomany MBZ's Avatar
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Location: central Va
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Have the same problem in the '82, haven't torn into it yet, will check this post for updates. I live in Hopewell, Va. Perhaps we can chat in person. PM
Heat is uncontrollable, is extremely hot, temp is almost unbearable coming out of the vents. Voltage going to the monovalve is 13v, but the ACC will not change the voltage. Pulled the ACC, rotated the wheel, and get 1.5k of resistance top to bottom in minimum, varying to 8k in maximum. Same measurements on pins 1 and 2 off of the board on the left, where it plugs into the harness. I can hear relays clicking when I go to min and max when it's energized. Blower fan works on high and low, auto doesn't seem to matter a whole lot.
Does it sound like I need a new ACC? I have one torn apart on the bench, and there are no burnt traces or anything.
TIA[/quote]

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  #17  
Old 01-07-2007, 07:41 AM
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Quote:
Originally Posted by toomany MBZ View Post
Heat is uncontrollable, is extremely hot, temp is almost unbearable coming out of the vents. Voltage going to the monovalve is 13v, but the ACC will not change the voltage.
It's not going to change the voltage. It's desperately trying to close the monovalve, but, the monovalve is not cooperating.

The problem is with the monovalve. You've got to determine why it's not closing when 12V is applied to it.
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  #18  
Old 01-07-2007, 08:23 AM
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Mine works on max heat only. I turn the temp wheel down and loose heat but the fan is still trying to blow air. And it's cold in the California Sierras, burrr. Any Idea's?
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  #19  
Old 01-07-2007, 09:32 AM
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Originally Posted by FineOlBenz View Post
Mine works on max heat only. I turn the temp wheel down and loose heat but the fan is still trying to blow air. And it's cold in the California Sierras, burrr. Any Idea's?
If you get good heat on max but no heat in other positions, the monovalve is functioning properly.

The problem is either the CCU or the inside cabin temperature sensor. The CCU bypasses the inside temp sensor when the temperature wheel is at the click stop. I'd check the sensor first. Maybe it's dead.
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  #20  
Old 01-07-2007, 10:21 AM
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People laughed at me

.... And people laughed at me when I wrote that MB has chronic a/c and air flow problems.

jeff
1991 300d, 100k, with a/c fixed
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  #21  
Old 01-07-2007, 11:50 AM
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word of caution

when applying the 12v to the monovalve,just touch it and get off, manual cautions about damage if voltage is applied permanent. this is from memory, check me out.
larry perkins
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  #22  
Old 01-07-2007, 07:24 PM
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Diesel way of Life
 
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Location: Cleveland, NY
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Thanks. I haven't had a chance to look at the car again, been too busy mudding my drywall. This remodeling is killing me. But, I'm getting pretty good at doing corners now.. lol
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  #23  
Old 01-08-2007, 08:43 AM
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Location: CT
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Just joining in to comiserate. Mine is more of an intermittent problem right now, but I've bookmarked this thread for future reference.
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  #24  
Old 01-09-2007, 02:09 PM
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Diesel way of Life
 
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Location: Cleveland, NY
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Thank you Brian Carlton. Me, being the dummie I am, replaced parts with ones I thought were good. Turns out, my "good" monovalve's solenoid would not energize. The "new" one I have, I applied voltage to and it clicks just fine. Seems like the heat varies with temp dial now, though I didn't take it on the obligatory test drive yet.

NOTE TO SELF: Test parts before installing... Boy do I feel
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  #25  
Old 01-10-2007, 11:05 AM
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Join Date: Dec 2006
Location: Sweden
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My MB 250D-92 had the same probs,the air from the vents was hotter then hell...
Monovalve should always have 12-14 V on the middle pole of contact, and the electronic circuit grounds the valve when it closes....intermittent.
The temperature on the air depends of the time ratio the valve is open/ closed.....so the walves should "klick" intermittent when itīs functioning...
If you not have 12v on the middle pole with ignition "on", check the fuse....

Excuse for my bad English, im one of the Swedes reading this exxelent forum =)
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  #26  
Old 01-23-2007, 02:18 PM
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Join Date: Jun 2004
Location: Cleveland, NY
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Quote:
Originally Posted by Shorebilly View Post
Have you checked your "In car temperature sensor" ?

If the Klima Control thinks it's too cold in your car.....all you will get is heat...
SB

SB, where is this thing located? I've got the car torn apart, and have traced the tube to the passenger footwell, with no sign of a sensor. Have I not gone far enough?

On a side note, here's a vac question. Forgive me, but I'm trying to understand the heating system. When the heat is always coming out of the defrost vents, is it the defrost vac pod that is leaking, causing it to stay open, or is it a different one leaking causing its door to not function?

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