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87 300SDL Climate Control weirdness
Searched the threads and couldn't find a definitive string to help. Got *really* warm here in Detroit for the first time, mid '80's, and I had the AC on. Working fine except now the fan is stuck on "medium" speed and I can't shut off the climate control. Press high and it goes to high and press low and it stays on "medium" speed. Temp works fine, various directional levels work fine. Just won't shut off and won't even go to "low" on the fan speed. Also, rear seat duct not working but I think that one is due to the lever.
TIA
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"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
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Sounds like the typical solder joint failure that brought me to this wonderful site in the first place. If you search a while on ccu solder joint repair or re-solder or something like that you will find allot of info on how to repair yourself through various links and old threads. Though my 87 300D ccu was different than the pictures shown for w123 ccu, the repair is very similar and I think possibly easier due to only one board to mess with. I am unfamiliar with sd/sdl models and if they are same/more similar to w123 in 87. Though I am not a professional at soldering, with a good magnifier lots of light and patience my ccu still works flawless two years later. Oh and the not shutting off is telltale solder joint symptom. There was cracked joints all over from thumbwheel temperature control, speed buttons, aux pump area (little hot spot also) and pushbuttons which I believe cause the no shut off problem. If you are unsure of your soldering capabilities you may want to experiment with a junkyard ccu first. I had nothing to lose as mine didn’t control anything anymore and wouldn’t shut off. In Las Vegas a/c is a requirement. Hope this helps
Arlo
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W211 E550 HVAC/R Certified Technician |
#3
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Picked up a used CCU, plugged it in and still can't get the fan to turn off. It is basically stuck on "auto" . Can turn on HI but hit the off button and the damn thing won't turn off. Arrgh!
__________________
"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
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Oh, and the one that was on the car appears to have been rebuilt at some point by someone who does it for a living - silver non MB looking sticker over screws on back saying warranty void if removed, etc.
__________________
"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
#5
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Ben,
There is an electronic module in the car that is connected to the push-button CCU that controls the blower motor. It actually connects to a resistor block and it is connected to the blower motor. My guess is that this module is the source of your problems. We can try to figure this one out if you want. Come over tomorrow afternoon and we can can sort it all out.
__________________
Michael LaFleur '05 E320 CDI - 86,000 miles '86 300SDL - 360,000 miles '85 300SD - 150,000 miles (sold) '89 190D - 120,000 miles (sold) '85 300SD - 317,000 miles (sold) '98 ML320 - 270,000 miles (sold) '75 300D - 170,000 miles (sold) '83 Harley Davidson FLTC (Broken again) :-( '61 Plymouth Valiant - 60k mikes 2004 Papillon (Oliver) 2005 Tzitzu (Griffon) 2009 Welsh Corgi (Buba) |
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Will do. I'll ping ya offline. Thanks!
__________________
"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
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Quote:
__________________
"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
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HUGE thanks to mplafleur for his technical expertise! Diagnosis - porcupine. Now to the hunt for a "new" porcupine (Blower Motor Regulator). New are $363! Yikes. Go to plan B.
__________________
"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
#9
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Yup. The fan motor control was getting the correct voltages depending upon which buttons were pressed (Off = 0v, Low = 1.2v, Auto = 2.0v, High = 7v), but the fan would never spin less than a medium-high speed.
__________________
Michael LaFleur '05 E320 CDI - 86,000 miles '86 300SDL - 360,000 miles '85 300SD - 150,000 miles (sold) '89 190D - 120,000 miles (sold) '85 300SD - 317,000 miles (sold) '98 ML320 - 270,000 miles (sold) '75 300D - 170,000 miles (sold) '83 Harley Davidson FLTC (Broken again) :-( '61 Plymouth Valiant - 60k mikes 2004 Papillon (Oliver) 2005 Tzitzu (Griffon) 2009 Welsh Corgi (Buba) |
#10
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On the potentiometer thought - stumbled across this when I got home this afternoon:
looking for a compound potentiometer
__________________
"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
#11
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Mike you were absolutely correct! Met up with Roy today and got a gently used porcupine and working magnificiently. In a weird way glad it happened so I could clean up all the mouse crap! Thanks again. Really appreciate it!
__________________
"Opportunity is missed by most people because it is dressed in overalls and looks like work" - Thomas Edison- 1979 300SD 1975 450SL 2014 Ram Cummins Megacab (tow rig) |
#12
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Quote:
Arlo
__________________
W211 E550 HVAC/R Certified Technician |
#13
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I'm glad Roy was able to find one for you and help you out. I'm going to have to keep an eye out for those at the pick and pulls.
__________________
Michael LaFleur '05 E320 CDI - 86,000 miles '86 300SDL - 360,000 miles '85 300SD - 150,000 miles (sold) '89 190D - 120,000 miles (sold) '85 300SD - 317,000 miles (sold) '98 ML320 - 270,000 miles (sold) '75 300D - 170,000 miles (sold) '83 Harley Davidson FLTC (Broken again) :-( '61 Plymouth Valiant - 60k mikes 2004 Papillon (Oliver) 2005 Tzitzu (Griffon) 2009 Welsh Corgi (Buba) |
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