I am having trouble with climate control system on my 78' 300D not always responding to current temperature conditions. I wanted to start out by checking the monovalve. For the 78 model I am suspecting that it is under the dash as it is not on the firewall by the battery as in the other pictures and posts that I have seen.

If it is cold in the morning, the heater usually comes on. If it is warm in the afternoon, the heater usually stays off. However, it seems like the valve is sticking at times.

Any suggestions welcome.

Don Dawkins

78' 300D

If, in fact, you have a 78 diesel, your car does not have a mono valve.

__________________
81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

I guess that would explain no monovalve on the firewall. What is the basic setup for the auto climate control as far as heater is concerned? I have not yet begun digging into the system since it is usually working. The temp wheel on the dash does not seem to be regulating the temp very well at this time. My main concern is that the heat is not always turning off and in Austin Texas, we have pretty mild winters and hot summers.

Hey Don,
You might get better results over at the "Vintage Mercedes" forum.

__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination

Danny,

Thanks for the suggestion.

Do a search on ACC servo or Climate Control Servo. You will find a lot of information. It's a big thing on the right inner fender near the AC compressor with the auxilliary pump just in front of it and a million vacuum and electric lines going into it. Nothing you learn about it will make you happy, but you might as well get to know it.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

LOL!!!
I have a good one if you need it... in my 78D parts car, going once...
John

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Sounds like the fun is only starting! Thanks for the help on this one. I was hoping to put off getting intimate with the ACC servo until some later time but I guess no time is better than the present.

Thanks,
Don