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#1
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Climate Control Acting Up - Ideas?
Hi... 86 300SDL - MY climate control worked fine all summer with the AC blasting but now that colder weather is here in upstate NY its doing some funky things.
-When I turn the car on it doesn't blow any hot air until the engine is ALL THE WAY up to temp (about 90c, takes 20 minutes of driving, and by that time Im already at work)... it used to start blowing hot air as soon as the engine was just a little warm (after 3-5 minutes). -Sometimes it doesnt blow anything at all, even once up to operating temp... I can feel hot air leaking out of the vents to the side and near the windshield when I am on the highway but the fan does not run at all. When this happens if I pull over and shut the car off then turn it back on the fan will usually then start blowing (I may have to turn off then on twice to get it working). It doesn't matter weather I have the fan setting on auto, low or high. -Sometimes when I turn the car on I hear clicking in the climate control area and the little light on the recirculate switch pulsates... if I turn the car off and back on this stops. -I get the the same results no matter which button on the climate control is selected and it doesnt seem to matter where the temp wheel is either. -Once I do the ritual of restarting the car after it is up to temp to get climate control working again it functions very well with all buttons doing what they should and the temp wheel works as well. So does anyone know where I go from here... any easy tests I should do to narrow it down? should I get behind the dash and check/clean connections? what else? is my climate control unit shot? TIA for any ideas!! It just sounds like thtings are going kaflooey behind the dash... maybe a gremlin. My garage is heated this winter with a wood stove so I'll have plenty of time to get the dash off and get this fixed. Hopefully I don't have to replace the whole unit. thanks! -Scott
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1986 300SDL - Royal Blue - 125kmi - "The Diplomat" |
#2
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Sounds like you need to check two things; Monovalve and Aux water pump.
When the aux water pump seizes, it draws more amperage than it normally should and then it shorts out the CCU pushbutton unit. Turning the car off and then on again resets the CCU. I have this same issue at this moment on my 86 300sdl. I unplugged the electrical lead to the aux water pump and the system is working just fine now. It's just that the heat to my windshield is not as hot at idle as it used to be. You can find the electrical connector to the aux water pump right next to the Monovalve which sits on the inside of the second firewall on the passenger side under the hood of the car. It sits next to the battery. As for the monovalve itself, it may have a rupture in the rubber diaphragm in it which could cause some heat issues also, like heat allways on or no heat at all, but usually the fan will work. I really think it is the aux water pump. Luckily on our cars, post 1986, there is a circuit breaker built into the CCU pushbutton unit so that it only shuts off the system instead of actually burning up the circuit board in it.
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John 1986 300sdl 1985 380se |
#3
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Not too long ago, someone else had similar issues and it turned out to be the electrical portion of the key switch. Yours sounds very similar.
Also, check the charging voltage as I noticed that an alternator not charging enough caused wierd problems with the climate control on mine. Cleaning the mounting/grounding surface for the voltage regulator resolved the problem.
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Sam 84 300SD 350K+ miles ( Blue Belle ) |
#4
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John - sounds like its probably the aux water pump like you said. I'm guessing the monovalve is OK because the temperature is working correctly. I will try to disconnect the Aux pump and see if that fixes the issue. IF I can live without it... GREAT! if not ill have to look into replacements. I don't drive the when there is snow on the ground so maybe I don't even need it.
Sam- Where is the voltage regulator? is that part of the alternator? the alternator on my car was replaced right before I bought it about a year ago. It only has about 10k on it. the whole car only has 130k total shes just a baby. thanks for the insight guys! Much appreciated. I will report back what I find. -Scott
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1986 300SDL - Royal Blue - 125kmi - "The Diplomat" |
#5
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Intermittant ccu could likely be due to broken solder joints. Search regarding the CCU re-solder job. It's pretty easy to do.
Also, I recently found loose harness connectors on my wagons ccu. Not too difficult to crimp the female connectors. Just make note of where all 12 wires go first in case they come out of the connector. |
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Quote:
The voltage regulator fastens to the back of the alternator with 2 screws. (Reminder: Be sure to disconnect the battery if you work with the alternator.) One side of the mounting face of the regulator grounds to the chassis of the alternator. It's pretty easy to remove the two screws, tilt it out and clean the mounting surfaces. I used a very thin film of conductive grease on both surfaces before reassembly to keep the corrosion at bay. With the alternator mounted low, it's in a susceptible area.
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Sam 84 300SD 350K+ miles ( Blue Belle ) |
#7
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Well... I think I found the plug for the Aux Water Pump... Looking at the windshield, between the battery and the monovalve. I unplugged it and gave it 12 volts... I hear absolutely nothing so I'm guessing its D.E.D. Dead! I think I saw something on here about testing the amperage to see if its dead but I dont have a tester handy... so my plan is to just leave it disconnected for a bit and see if that solves my issue. If so I'll have to decide if I want to replace the bugger or not. Thanks for the help guys.
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1986 300SDL - Royal Blue - 125kmi - "The Diplomat" |
#8
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Update... UhOh! well I drove the car about 20 minutes to my GF's house last night and the heat and CC was working like normal . Parked the car for the night and drove into work this morning.. NO HEAT. I couldnt get the CCU to do anything at all no matter how many times I restarted the car... ugh. any ideas what next? thanks.
I guess Ill start by plugging the aux water pump back in... maybe it wasnt bad as I thought. if it was working would it make noise if I give it 12 volts? I did that last night and couldnt hear anything so I thought it was dead...
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1986 300SDL - Royal Blue - 125kmi - "The Diplomat" |
#9
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I'll second this.
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83 SD 84 CD |
#10
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OK, im ready to remove the CCU and resolder. Ive been searching here and w google but I cant find a good description of how to remove the CCU in a 86 300SDL... I remember at one point a long time ago seeing a great tutorial somewhere with pictures and everything but I cant find it. Do I need to remove the whole dash or just some of the center console. I want to know for sure before I go prodding at things and taking everything apart. thanks.
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1986 300SDL - Royal Blue - 125kmi - "The Diplomat" |
#11
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Remove the radio. Then you can remove the screws that hold the trim in place. Then you should be able to see how to remove it.
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Greg 2012 S350 BlueTEC 4Matic 2007 ML 320 CDI 2007 Leisure Travel Serenity 2006 Sprinter 432k 2005 E320 CDI 1998 SLK230 (teal) 1998 SLK230 (silver) 1996 E300D 99k, 30k on WVO Previous: 1983 240D, on WVO 1982 300D, on WVO 1983 300CD, on WVO 1986 300SDL 237k, 25k on WVO (Deerslayer) 1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix 1983 380 SEC w/603 diesel, 8k on WVO 1996 E300D 351k, 177k on WVO |
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