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Old 09-24-2003, 04:27 PM
Old Deis
Posts: n/a
Swapped out the ACC

Yup. Had enough of that mess on the old 1978 300D.
I inherited a very nice, but wrecked 1981 european 300D. It came with a heat/ac that has knobs to control the heat system. I had studied that car for a year and decided to attempt the swap.
The final insult came when the last component on the old 300D ACC failed. The control valve was out, the fan quit, and then the push buttons gave way. The repair costs were getting way out of line here and it was time to move.
So two weeks ago I pulled the old diesel into my garage and removed the old blue dash that was badly cracked. Then I pulled out the ACC and that wiring harness. Next came the old heater box and the heater core and the old heater hoses.
Then I nealry had a panic attack. If you have never seen a car with the dash and that much removed from your car you know why I say that. Makes what was once a car you could drive look like one that is ready to load onto a big truck and hand the driver the title.
After getting my nerve back I started to replace the stuff with the 81 heater assembly. I had the donor car right there, so I could still check on that. I had pulled out most of the parts last year so I began installing stuff. Went quickly. Everything except for the dash out bracket on right side had the bolt holes already there. Amazing. I was especially pleased to find the heater contol assembly had the little mounting bracket there and the hole were in place to put the screws in to hold it on the firewall. Cables easily went right in. I had the donor wiring harnes for the heater contols and the dash lights, some troubleshooting there to get it right, but it all works.
I used the black dash and the center console from the 81. Dash went right in place. That right side bracket was not hard to mount.Just drilled a couple of holes and made it work.
The only thing to get now is a fan, some pervert stole the blower out of the donor car before I got it. I discarded the AC. I had already given up, and besides around here AC is just not worth the expense of a rebuild. But everthing else does work now.

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Old 09-24-2003, 09:21 PM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,352
Way to go.
I'm considering, as my fall "project", pulling the dash on my 300D and try to come up with a manual climate control system for it.
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Old 09-25-2003, 06:41 PM
Old Deis
Posts: n/a
Just get ready for some anxious moments. Think of all those wiring harnesses and you may well imagine.
The thing that convinced me to try was the amazing simplicity of the manual controls on the Euro donor car. Haven't looked under the hood of a 240D or some other model MB without ACC, but I would bet they all have the same setup. Real easy to make that work. Just all those wires....
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Old 09-25-2003, 07:58 PM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,352
A couple thoughts I have had with one of these conversions.

My idea is to use pneumatic switches to operate the vacuum pods. You can get small ones that can easily fit on a new panel to make up in place of the existing set up. The blower speed should be easy with a three way switch using the existing resistor bank and the temp dial is just a matter of figuring out what kind of voltage I have to put to the monovalve to move it through its full range of travel. An alternative is to put a manually operated valve in place of the monovalve and run a cable to the cockpit to open/close it. The existing auxilary water pump has been disconnected for a long time. My thought to power the compressor is just a switch that operates a relay going through the evaporator temp sensor, through the pressure switch and then on to the compressor. Only thing left would the aux fan that comes on at high a/c pressure.

Right now everything is working fine so it is one of those things that I may eventually get around to.
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Old 09-25-2003, 11:47 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,834
I remember those days. I have a manual AC control panel for a 126. The blower part is easy and the blower switch has an integral vacuum switch so it's in recirc mode in the 0 position and fresh air mode in the detent between 0 and I and beyond. I'm guessing the temp control wheel has the same resistance ranges as the temp control wheel in an ACC system so it can feed directly to the temp controller.

The big question is the vent selector. It has two bowden cables. I can't figure out how to hook it up to 4 flaps. I was thinking of something like an 8 pole 8 throw rotary switch to control the existing vacuum switch bank. Or even a 4 pole 4 throw rotary switch. I gave up when I couldn't find a big enough switch for a reasonable price.

Next idea is to use an ACC control panel but hog out the case so each button controls the actuator switch bank directly without second guessing my intentions. I can probably fit a second thumbwheel in place of the fan control buttons for real fan control ala W109.

When someone posts of ACC problems I burn incense around the manual AC controls If the appropriate deities accept the offering, maybe MB will offer manual AC in the US again.

... bitter enough for ya?

95 S420
91 300SE
87 300SDL
83 300SD

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