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  #1  
Old 05-06-2003, 05:03 PM
sab sab is offline
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Location: Ft Lauderdale
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Unhappy No Heat - W140

My '95 S320 has absolutely no heat. The AC works fine and the blower motor and regulator (just replaced) works well.
I looked at all coolant hoses coming and going to the monovalve and can't seem to figure out which ones should deliver water into the valve and which ones should send the water to the heat exchanger.
It also looks as if the valve operates two completely seperate circuits and it just seems so odd that they would both fail at the same time.
I found some info in the archives that the valve goes to the open position if it gets no power.
HMMMM.
I remember it stopped functioning shortly or right after a plastic y-connector on one of the small coolant lines broke and was replaced. That Y-connector is on the driver side in the engine compartment on the firewall.
Could a piece of plastic have come loose and be blocking the water flow somwhere?
I pulled one line coming from that Y connector going to the valve and it has no water coming out unless I squeeze on the main coolant line in front of the engine it then seeps out a bit of water. (with the engine warmed up).
Any help troubleshooting this odd problem would be great, its an anoying problem (even though it could be worse... always hot...), which would not be really nice in the Miami summer.
Thanks and regards,
Sab.
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regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged
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  #2  
Old 05-06-2003, 07:24 PM
sab sab is offline
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Both sides no heat

Correct, I have no heat on both sides. That's why I am somewhat hesitating to order the new valve, since I think it would be strange to have failed in both sides.
How would I check if there is water coming to the valve?
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regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged
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  #3  
Old 05-06-2003, 07:28 PM
sab sab is offline
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why is my post showing before sclassforever even though I replied to his post????
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regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged
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  #4  
Old 05-06-2003, 08:29 PM
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Join Date: Jun 2001
Posts: 46
no heat on either side?

Have you no heat on both sides, driver and passenger ? Remember they have individual ducts and controls. On my W140 I get heat only out of one side..Its more of a duo-valve than a monovalve, but I think I have to replace the whole thing, I dont think you can replace just the bad half. Hold your hand over both side of defroster ducts and check to see if both sides are bad. These monovalves are expensive, around $453 if I remember. If both sides are cold maybe it is something else.
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  #5  
Old 05-06-2003, 09:34 PM
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Join Date: Jan 2002
Location: NY
Posts: 500
You can put ACC in a test mode and read sensor values and fault codes. Follow procedure on JimF page:
http://pages.prodigy.net/jforgione/MB_AAC.html
Mike
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  #6  
Old 05-06-2003, 10:21 PM
sab sab is offline
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DTCs readout does not work.

Thanks for your response Mike,
I did try to get the TDCs, but I couldn't. It would always display the sensor values. I followed his directions both for the sensor readouts and the TDCs, but it always displayed the sensor values.
I gues it's the last step: "Wait 20 seconds, then simultaneously press [REST] and [O] buttons for more than 3 seconds." Trying to hit the two buttons simultaneous, I guess one gets pressed first. If I press the rest button first I get the sensor values, and the [0] the system turns off.
regards,
Sab.
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regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged
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  #7  
Old 05-06-2003, 10:59 PM
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Join Date: Jan 2002
Location: NY
Posts: 500
Sab, I tried it in my car (1992). Thats what I did:
1) Turn ignition ON and shut down AAC by pressing 0 button;
2) Turn OFF ignition;
3) Set left wheel to red detent and right wheel to blue detent;
4) Turn ON ignition;
5) Press AUTO (displays show HI/LO);
6) Within 20 s simultaneously press REST and 0 for >2 sec.
It worked for me.
What did your read from sensors?
Mike
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  #8  
Old 05-07-2003, 12:26 AM
sab sab is offline
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Join Date: Apr 2003
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I just tried it again just as you describe it and only the sensor values come up. I didn't write them down this time, but I did the last time and they looked just fine.
I searched the archives and saw someones post having the same problem as I do, but unfortunately he did not post how he resolved showing the TDCs.
Aparently some of the AC components changed with the '95 models. Anyone knows what I need to do to get the errors.
Thanks,
Sab.
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Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged
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  #9  
Old 05-07-2003, 09:15 AM
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MB manual gives this procedures for W140 up to 8/95.
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  #10  
Old 05-07-2003, 09:59 AM
sab sab is offline
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So what could be wrong that I cann't get the TDCs to come up? I am pretty sure I am following the procedure correctly.
Thanks,
Sab.
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regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged
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  #11  
Old 05-07-2003, 12:11 PM
RDA
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I have a 92 S600 and I have also never been able to get the fault codes to show up, only the sensor values.

My problem was no heat comming out of the foot vents. I have through trial and error managed to get heat by closing the centre vents, pressing both buttons for lower heat and pressing the red button on the upper centre facia vents.

I don't know why this works. It's less than ideal, but without a diagram, and not being able to access the fault codes it's the best I could do.

Cheers.
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  #12  
Old 05-07-2003, 12:27 PM
oldsouth's Avatar
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Join Date: Feb 2001
Posts: 610
Check the heater pump on the rest valve. Drivers side under the cover near the front of the car. You can remove it by un-screwing the 4 torx screws. Press the rest function on the a/c controler and see if it turns.
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1995 S-350
370K + SOLD
1952 220B Cabriolet
39K kilometers + SOLD
1998 E300D
285K +
2006 E320CDI
130K +
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  #13  
Old 05-07-2003, 02:01 PM
sab sab is offline
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Heater pump???

So the "heater valve" I was looking at, which I thought to be three valves is a pump and two valves?
Is that all one replacement part or can I get individual pieces for the pump and the valves?
Thanks,
Sab.
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regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged
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  #14  
Old 05-07-2003, 02:11 PM
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The tall one is the pump. Mine was starting to squeal recently and I bought a new one. After taking the old one off, I discovered that the part that turns just needed to be oiled. I installed the new one anyway. If you are interested in the old one cheap - e-mail me.
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1995 S-350
370K + SOLD
1952 220B Cabriolet
39K kilometers + SOLD
1998 E300D
285K +
2006 E320CDI
130K +
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  #15  
Old 05-28-2003, 12:56 PM
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Join Date: Jun 2001
Posts: 46
Sab did you ever get this sorted out? I just drained my coolant and remembered my 93 400SEL still has a heating problem, I am only getting heat from passenger side vent. Im tempted to try a new duo-valve. Do you guys think this is the problem? I just lost my job (laid off, probably permanently), and at $439, I cant afford to make a mistake. I wonder if it wasnt the problem if I could wash it off and return it to the dealer. I may try to run those diagnostic tests but my gosh, they seem very complicated. Any help is much appreciated!
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