Climate Control/Monovalve - PeachParts Mercedes-Benz Forum

retx · #1 11-30-2006, 11:57 AM

I can not find my monovalve. I have looked where everyone says. I have searched exactly where my Haynes manual says it should be. NADA. not there. I have read that not all of them have a monovalve. Is this my case? Its a 1980 300D. When i bought it a month ago, the heat was good. Then it got weaker, and now its just blowing cool air. My unit has the temp. wheel to the left (oriented up and down) and the buttons to the right (also up and down). I have only seen one other like this. Does that mean no monovalve? If there's no monovalve, then where do i go from here to fix my heat?

pwogaman · #2 11-30-2006, 12:36 PM

The monovalve is in the engine compartment on the upper firewall on the passenger side. It has hoses running into it. There are 4 flathead screws and a two wire plug. Pull out the plug, unscrew the screws, and pull up to inspect. If the rubber is ripped just replace it and you're done. 1 on a scale of 1 to 10.

Moorewr · #3 11-30-2006, 12:49 PM

You probably are like my 77 300D, the servo, black box on rt front fender well area, if so, probably have a bad servo, numerous ways to get around the 1700 MB for OEM, I bought the replacement, digital unit from diesel giant for 650.
Ron Moore

RAYMOND485 · #4 11-30-2006, 01:39 PM

1984 300d Turbo 141,000
Go To This Site Buy Parts, Climate Control, Mono Valve R3023-15174
$63.65 Electromagnetic Heater Valve Diy

carnut · #5 11-30-2006, 01:49 PM

Your car has first generation auto climate control. NO mono valve. Check the aux. water pump mounted vertically beside the climate servo underhood. Unplug it and jumper 12 volts to it, you should hear it turn on. If it runs then probably a faulty servo.

tobybul · #6 11-30-2006, 02:30 PM

if its a bad aux wtr pmp, there are many threads on how to repair it. I wrote one recently with pics. my heat is much better now after i got the pmp working.

retx · #7 11-30-2006, 05:45 PM

Quote:

Originally Posted by carnut

Your car has first generation auto climate control. NO mono valve. Check the aux. water pump mounted vertically beside the climate servo underhood. Unplug it and jumper 12 volts to it, you should hear it turn on. If it runs then probably a faulty servo.

i was thinking i read somewhere that some MBs did not have monovalves. i got up under there today before i came into work and i should have taken a pic of the engine and supposed location of the monovalve. i swear guys....i have nothing mounted there.
tobybul-could you locate that thread you posted about replacing the aux water pump? i couldnt find it just now. also, whats the cost of a new or rebuilt aux water pump?
i was hoping i could just rebuild a monovalve this weekend since its so cheap and i assume a lot easier than the aux water pump.
thanx guys.

kerry · #8 11-30-2006, 06:13 PM

You're going to wish you had a monovalve. The problem is most likely your ACC servo. Not cheap to replace. Do a search on ACC servo or climate control servo and cry to your heart's content.
Best replacements are the new aluminum bodied servos or the electronic substitute. Ask for one for Xmas.

retx · #9 11-30-2006, 06:25 PM

Quote:

Originally Posted by kerry edwards

You're going to wish you had a monovalve. The problem is most likely your ACC servo. Not cheap to replace. Do a search on ACC servo or climate control servo and cry to your heart's content.
Best replacements are the new aluminum bodied servos or the electronic substitute. Ask for one for Xmas.

Ok Santa Kerry, can you get me one? i'm moving to Denver next May anyway, so you can just keep it til then and help put it in.
Ok jokes aside. I will try to search out some more on it.

JimmyL · #10 11-30-2006, 06:50 PM

Quote:

Originally Posted by retx

I will try to search out some more on it.

Just search the word "servo" in Diesel Discussion and you will get a ton of hits.
Like this for example: complete servo replacement/ swap?

You don't have the monovalve, as mentioned above on more than one occasion. The Mercedes Source kit, mentioned in link, is $75 bucks, and will give you manual control of heat.
You will have to deal with AC at another time. You can get cheap heat now, and bide your time and maybe you will come across an aluminum bodied one on ebay or here, or the yards......or the kit from Diesel Giant.
Good luck.

Did I mention, you don't have a monovalve?

retx · #11 11-30-2006, 07:20 PM

Quote:

Originally Posted by JimmyL

Did I mention, you don't have a monovalve?

yea, im getting the feeling thats what a lot of you are saying. something about no monovalve. haha.
well that just blows. poor me. now 650 just to be warm damn. does running it with a bad servo create any problems for the car? i may just have to bundle up and go without for a while, when i get back from new years. definitely have to fix it before i head to denver. will the servo be after my "t" for hih heated lines when i install my veg conversion?

cconbalsam · #12 11-30-2006, 11:26 PM

While my servo worked I had the coolant line t between the servo and the auxilliary water pump. It worked well. Now I have bypassed the servo and installed a manual valve. The loop running to my veg tank provides a bypass so the pump never has a chance to deadhead when I have the heat off.