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#16
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Like pawoSD, I suspect it is drawing in outside air when it shouldn't. Read the Owner's Manual since the temp controls are non-intuitive, though the problem is likely not user-error.
As mentioned, in the engine bay, feel the tubes going into and out of the heater core. If both are warm/hot, the problem is in the cabin in the air box (flappers doors, controller). If they stay cold, and the mono-valve is unplugged, and you rev the engine a bit (water pump doesn't cirulate much at idle), the problem may be a clog, either in the heater core or in the electric auxiliary pump blades (near alternator). I removed mine (leaking shaft seal) and replaced with heater hose. I get plenty of heat (when the controller cooperates), just not much at idle. |
#17
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Pelican Parts - Automotive Parts and Accessories - Porsche & BMW
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles |
#18
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Be mindful that the monovalve is closed electromagnetically and spring-loaded to the open position. If you don't believe that the monovalve is the problem, replace it with a piece of copper tubing and you will have more heat than you can stand. I guarantee it. Your problem isn't electrical. It isn't airflow related. It's the monovalve. |
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That's a little hard to do at highway speeds.
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#20
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Aftermarket parts are often worth less than the box they came in. A poor quality monovalve insert will cause precisely the symptoms that you report.
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#21
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A friend has this exact issue in his '84 300D. He's replaced the diaphragm on his monovalve using the aftermarket rebuild kit from Pelican. His ACC is working flawlessly in every other way. All dash pods are working, including recir. He gets perfect heat on surface streets, luke warm air on the freeway. If he unplugs the monovalve, he gets full on blazing heat all the time. There is something not working correctly in his monovalve that is not related to a torn diaphragm. Hopefully this thread will lead to something that can help both of these guys.
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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino http://i.imgur.com/LslW733.jpg The Baja Arizona Oil Burners Send a message if you'd like to join the fun Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130 Visit the W123 page on iFixit for over 70 helpful DIY guides! |
#22
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#23
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Thats what mercedes calls it.
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles |
#24
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Is there a source for just the monovalve diaphragm rubber?
Seems like the Bosch units have a C or E clip that can be removed, and the diaphragm (which is almost always torn on bad monovalve diagnoses) can be replaced. I just found out mine is torn (again), even on a Bosch unit I replaced a few years ago. MTC seems like the only unit available but I don't want to get the whole thing if there is a source for the diaphragms only. Has anybody sourced these? Thanks
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/ there is one thing which happened to me with monovalve it melted completely and the plunger inside of the coil stayed in closed position in a way that spring was weak to re-position it on lack of voltage. it was not obvious from the outside,..it melted inside the housing. .
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w126 500SEC gen II euro, powered by OM617 turbo stolen from 84 300SD 2.88 diff,EGR blinded next wish/project: w114 coupe OM603 powered |
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I got new one from MB, $108 through my parts guy. Same rubber labeling as my old Bosch unit, which also ruptured years later. MB has 1 year warranty on item.
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#27
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Wikis on electromagnets and solenoids: Electromagnet - Wikipedia, the free encyclopedia Solenoid - Wikipedia, the free encyclopedia An electromagnet is basically a coil of wire wound around an iron core (what you are incorrectly calling a magnet, the part that has to move, to do the actuation). This monovalve assembly is an electromagnet, or solenoid: Monovalve iron core actuator (what Mercedes calls a magnet? which it is not):
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked Last edited by funola; 12-25-2013 at 10:16 AM. |
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#29
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Just to be completely OCD on definitions:
An electromagnet is a device that has a core and coil. The core is fixed. Common examples are the big pickup device on the end of the crane in a scrap yard or the device that holds doors open and lets them close in case of fire. A solenoid is a coil with a movable core. Common examples are valve actuators or door chimes or the device that pulls the starter shaft in contact with the ring gear.
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The OM 642/722.9 powered family Still going strong 2014 ML350 Bluetec (wife's DD) 2013 E350 Bluetec (my DD) both my kids cars went to junkyard in 2023 2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles) 2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles) 1998 E300DT sold to TimFreeh 1987 300TD sold to vstech |
#30
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