Sorry if I ask questions that have been have been discussed before.
I have spent some time looking over old posts, but see mostly newer systems than mine.
I have a 77 300D non turbo. Witch if I understand correctly is the 1st year for ACC system. ??

I wonder if someone could point me in the right direction in finding a vac diagram or any advice as to where start diagnosing this older system? I have only owned this car since last fall, just in time to put it to bed for the winter. So have little time to drive it or spend much time looking it over.

What I know so far …. Defrost has super hot uncontrollable heat. Bi-level has super hot uncontrollable heat. Both have no fan control, high only. Temp wheel seems to do nothing.
When I change to “auto high” heat will come out lower foot vents for aprox 10-15 sec then shut down. Change back to bi-level and it will restart. Change to “auto-low” same thing. Will run on low fan for a few sec’s and stop.

The electric coolant pump does not work and is unplugged for now.
I removed the under dash cover on the right side to find 3 vac hoses not connected to anything and one caped off. 1 of the 2 vac pulls that I can see is capped off (far right upper one capped)
I un-caped the one hose, then the bi-level would fail just like the high and low does after a few sec’s.

Have never been able to get air (hot or cold) to come out of the center vents. The 2 side vents work with bi-level. The AC compressor seems to work when the dash switch is turned on. Also compressor cycles when the defrost or bi-level is on. This is about the only things that seem to be working normally.

Sorry for the long post, just want to try to give as much info as I can.

Thanks for any help

Bruce

Here is a link for information on your system:http://www.imperialclub.com/Repair/Lit/Master/281/index.htm

Also, try an advanced search with ACC W116 and there will be many posts, with contacts, for help with your system. I believe most of the posts were from the Vintage Section.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Do you have a 115 or a 123 model... I think that 1977 was the first year for the 123-300D Nonturbo.. I didn't realize that the 77 had a aux. water pump..
The easiest way to get everything working is to remove the dash and you will be able to see which vacuum actuators are unplugged and or are nonworking and need to be replaced.. I think you might have as many as 3or4 modules under the dash... these operate the various flaps or doors to close off or direct the heat/ac... Does your car have the infamous chrysler designed control system up on the passenger fenderwell near the AC Compressor???? Jim

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James A. Harris

It's a 77 300D W123 non turbo. Yes It does have some kind of valving system system behind the compressor along with the electric coolant pump.
It's a @#&^% scary looking hose monster
Is this the "mono valve" that I have read about in the newer models ?
Thanks

Thank you !!! I had no idea that this this was a Chrysler system. The control valve pictured on the 2nd page sure looks like my "hose monster"

THANKS again
Bruce

Yes, that is the infamous chrysler servo.. I think it has about 18 vacuum lines and 18 electric wires... check the bottom and if it has been leaking then the unit is usally bad... Jim

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James A. Harris

I pulled the valve out yesterday and to my surprise there are NO leaks !
Was expecting it to be all rusted up. Nothing, clockwork and motor all turn freely. Acts as if there is no power. Is there a hidden fuse some place?? I could not locate any blown fuses in the box.

Thanks for the help

I also have a 77 300D and know the parts you are talking about. Mine doesn't work perfect but it does work. If you have some questions and I can check it out just PM me. I don't get on this site every day but I do try to check it once a week.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

No monovalve on yours. No heat will ever come out of the center vents, just AC. ACC Servo runs on both vacuum and electricity so a vacuum problem can disable it (I think). Default setting is high heat defrost only. I currently have mine disconnected from the vacuum since there is a leak somewhere so I only have high heat defrost.
I don't know how the auxilliary coolant pump is wired into the system. I'ts remotely possible that disconnecting the pump might have an effect on the servo.

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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