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#1
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Crazy heater question, heats around town cold on the highway
Just a quick question, around town the heater works pretty well. Automatic climate control (I can't find any manual switches knobs or levers). 82 300TD The heat comes on and is toasty around town but on the highway it just blows luke warm cool. I'm wondering is there an outside cold air vent some where on the car I can just cover with card board, or manaully turn off?
I'm leaving to New Orleans tomorrow morning and am dreading the parka, gloves and hat on the freeway. Of course once I am there not really worried about the heater or the air conditioner to much, until about May, then I will be really concerned about AC. But that's in May.
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1982 300TD, Rescued from rusting away on Martha's Vinyard, roaming the highways again, this time with a saggy bottom... No SLS |
#2
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Sounds like your monovalve may not be opening fully, thus allowing a little hot water (but not enough) to enter the heater core. You can remove the electrical connector and four screws, then lift the monovalve out of its body (you'll lose a little bit of coolant but not enough to need to pre-drain the system) and look to see if it's all crudded up or has a corroded electrical solenoid that is blocking free travel of the plunger.
Another possibility is that the aux coolant pump is crudded up and is not allowing much hot coolant through the heater core. The fix is similar to the monovalve fix, just harder to get to. A third possibility is that the heater core is itself partially blocked. That is a much more difficult and expensive repair so let's check the monovalve and aux pump first. Jeremy
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"Buster" in the '95 Our all-Diesel family 1996 E300D (W210) . .338,000 miles Wife's car 2005 E320 CDI . . 113,000 miles My car Santa Rosa population 176,762 (2022) Total. . . . . . . . . . . . 627,762 "Oh lord won't you buy me a Mercedes Benz." -- Janis Joplin, October 1, 1970 |
#3
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Hey thanks I will investigate that in the morning. It's night and below freezing... I think I can pull that open fairly easy in the morning and see whats whats.
Thanks Matthew
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1982 300TD, Rescued from rusting away on Martha's Vinyard, roaming the highways again, this time with a saggy bottom... No SLS |
#4
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Sounds like the monovalve to me... It is probably ripped. you can get a new insert to fix this quickly. The other thing it could be is the small fan that samples air from the cabin. There is a hose that runs from the opening to the sampler fan. If the hose crumbles then the sampler draws warmer air from under the dash and cuts the heat. Do a search on this and you will see what I mean.
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"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy" Current Monika '74 450 SL BrownHilda '79 280SL FoxyCleopatra '99 Chevy Suburban Scarlett 2014 Jeep Cherokee Krystal 2004 Volvo S60 Gone '74 Jeep CJ5 '97 Jeep ZJ Laredo Rudolf ‘86 300SDL Bruno '81 300SD Fritzi '84 BMW '92 Subaru '96 Impala SS '71 Buick GS conv '67 GTO conv '63 Corvair conv '57 Nomad |
#5
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On a 123 with ACC III,(temp wheel on left, 5 buttons across, fan on right) there is a blend flap behind the glove box. it has a green vac line going to it.
remove the glove box, you'll want to replace the disintegrated foam tubing anyhow, and check to see if the flap is open or closed, and operating correctly. Mine wasnt closing, ever, so I disabled it. to permanently close it, you can simply unhook the vac line to it. That is what I did. then I melted the end of the vac line w/ a lighter and pinched it off. if I want to revert, I can simply cut 1/4" off the line and plug it back in. also check the monovalve- it will only take a few minutes.
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1984 123.193 372,xxx miles, room for Seven. 1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven. |
#6
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Quote:
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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate Sooner or later every car falls apart, ours does it later! -German Narrator in a MB Promotion Film about the then brand new W123. |
#7
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That's a classic symptom of a torn monovalve diaphragm. A monovalve repair kit will take care of the problem.
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#8
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hey guys thanks, I started totear into this before I hit the road and thought, **** it's freezing here in the parking lot and... **** it's freezing and if I just make a run for new orleans, it's warm there and this is far less of an issue in New Orleans in the winter than here in the winter besides I need a repair kit and can't get one of those on Sunday Morning at the end of cape cod.
So I made a run for it and the heat was good enough to get me here in one piece, I will order a repair kit and take care of it now that I know how to fix it. thanks for all the feed back and sharing your knowledge.
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1982 300TD, Rescued from rusting away on Martha's Vinyard, roaming the highways again, this time with a saggy bottom... No SLS |
#9
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Try unplugging the monovalve electrical connector.
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91 350SD 14 F150 Eco 19 Fusion Hybrid 11 GT500 |
#10
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Quote:
peeps smoke cigars in their cars all the time, and most dont start them on fire. just use common cent$.
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1984 123.193 372,xxx miles, room for Seven. 1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven. |
#11
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Quote:
Glad to hear you got it sorted out and what your fix was. Yes, you can use an open flame back there without disaster. Plugging it would be safer -- A BB, golf tee, pencil, aquarium valve, etc.
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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png Broadband: more lies faster. |
#12
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I took the monovalve off today and two things, I have that green antifreeze which I bet is wrong and I have a destroyed monovalve. I'll order a new one after the holidays and also change the coolent then too!
Thanks for all the tips.
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1982 300TD, Rescued from rusting away on Martha's Vinyard, roaming the highways again, this time with a saggy bottom... No SLS |
#13
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Welcome to town, hope you like it
Sounds like you have the exact same problem I do. I am sitting on a new monoalve myself and will probably install over the holidays. shoot me a PM and lets meet up. I live in the uptown area near Broadway and Clairborn ave. So what brings you to town? Work or pleasure. Also I can hook you up with a good mechanic if you need one for anything beyond your comfort zone.
C-ya R
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I would'nt say I've been missing work... 1982 300D Turbo Diesel |
#14
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Funny because I too have the exact same problem. Heater blows hot around town when I am just cruising around. Anything about 55 or so it blows kinda cold, but not enough on colder nights to really help. You guys ordering new mono valves from the dealer, or somewhere else? Thanks for the post. by the way, this has been driving up a wall for the last two weeks or so.
D |
#15
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No I will order the bosh replacement monovlave kit from the store on the site. It's 45.00 but won't put it in until I change antifreeze with the recommended type by MB.
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1982 300TD, Rescued from rusting away on Martha's Vinyard, roaming the highways again, this time with a saggy bottom... No SLS |
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