Mercedes 300D heater / climate control issues fixed!
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- เผยแพร่เมื่อ 12 ก.ย. 2024
- In this video I work on a 1984 Mercedes 300D W123 which has the often problematic automatic climate control system. But really it’s pretty easy to diagnose and repair. In this case I replaced the monovalve and everything work like it should again.
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thanks! great video. dont think either of these are my issue but great to know how to diagnose. My issue on the same car is that i have air out the middle two vents but very little out the bottom towards the feet! gets chilly driving in colder temperatures :/
I have a w126 ‘86 sdl and have not had ac for the hottest driest summer I can remember. First I took it to an old MB tech and he had it for a day and said come get it and charged me $200 and it worked, didn’t think to much of it and all was good. For about a month, so I take it to a good ac shop and they say leave it and we will check it out. So they call me the next day and say $300 all good. It lasted about 2 weeks, and I take it back and leave it. He replaced two hoses, compressor dryer, and condenser says he also talked to his buddy that works on old Benzs and he changed a big relay to a small relay, and charged me $600.00. It was in April 40 to 60 F. It never worked. I can do what I saw you do if you think it may help.
It sounds like your problem is no AC so this would not fix that. This will only fix a no heat issue. Never hurts to check your monovalve though, it's easy and one that doesn't work well will cause the whole climate control system to not work as it should.
Boko’s Diesel Garage thank you, I understand they are separate problems, I was counting on your experiences and knowledge to help me on the road to fixing this. Seems that spring and diaphragm should be bad every 30 years or so.
@@beaufubm5983 Yeah it's common for these to go bad and only an OEM replacement is going to last. It's easy to check so I would check yours, on the SD's its behind the firewall. I don't think it will fix your AC issues though. Good luck
Boko’s Diesel Garage thanks, your video has made me want to learn more about the car.
Beau Fubm did it work for you?
Great stuff! Very helpful.
Thank you!
Very good knowledgeable video thanks
Hello and thanks for the informative video. My 1987 300d has no heat or air. Climate control panel does nothing. I can feel heat from vents but no fan and buttons don't function. What's the best place to start.
Thanks for your time. Robert
I’d start with checking your fuses. Normally if you push the defrost button your fan will come on high. If it’s not doing anything you’re likely not getting electricity. But the switch panel or fan could be bad too. Do some testing with a multi-meter and you should be able to tell.
Is the monovalve the only thing that stops the engine shooting heat into the cabin? I want to replace it with a setting digital. Is that possible? @@bokosdieselgarage
Great info. 👍
Well done!
Super cool video
Nice video 👍👍👍💯💯💯
When I have my heater on and scroll the temperature all the way red it doesn’t blow heat most of the time so I will check the monovalve. Also when all that is on I hear a constant tapping noise in my dashboard. Is that the heater blower fan getting stuck or something? I’m assuming I need a new monovalve for the heat to work and a new heater blower fan for the noise to stop?
Yes start with checking your monovalve as it’s easy to do. But also for your climate control system to function properly you need to make sure you don’t have any vacuum leaks anywhere in your system. The tapping noise could indeed be the heater fan, but hard to say without hearing/seeing it.
So the center vents are only for cold air (a.c.) ? I have an '83 and I thought that mine are broke ( not blowing hot air on center vents )
Liviu that’s correct.
i have a 1984 w123 200 and my ac doesnt do anything in the summer here in egypt where the temprature is around 104 degrees Fahrenheit (40 degrees Celsius) so i was wondering is something wrong with my ac or is it normal for this car's ac to not be that cold.. also my side vents are barely blowing any cold air.
MAEAMAEAM it might need to be recharged if it’s been a while. With these cars getting so old it’s also common to have leaks.
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I have a 81 300d and my blower comes on and off kinda whenever it wants. Some of the buttons on the climate control dont work and the blower usually only likes working on low speed. If I put it on hi it will blow for a little than just shut off. I never loose heat I just loose blower motor. If I mess around with the climate buttons I can usually get the blower to stay on for a little bit but it eventually shuts off. Any help would he greatly appreciated
I’d open it up and check for loose vacuum lines and electrical connections. Maybe take it all apart and give it a good cleaning too.
Thank you for your fast reply I really appreciate it. Comming into winter makes this quite spooky lol. Ill look into it today
My AC doesn't blow through middle vents. Any clues?
Vacuum pod under the dash might be shot. You can force open the vents full time by pulling the glove box liner and disconnecting the pod, putting a golf tee in the vacuum line.
Weird I knew about certain vents blowing hot air or cold but my 85 300d blows hot air from all vents. Also my blowers only work sometimes. In any setting. It usually comes on about 10 minutes after driving but it will shut off sometimes. It's very sporadic and there isn't a pattern in if it will turn off ot not while I drive. Any idea?
You might have some broken solder joints inside the climate control unit. It’s the part I checked first in this video and ended up being fine in my case. If they’re cracked they can still work sporadically.