I went to pull the CCM to find the malfunction, but the plate come off the plug cover on the driver side and of course every wire popped out.

I have attached pictures, but I am pretty much screwed right now (no manuals).

While these wires are exposed, is there anyway I could attempt to jump a couple to trigger the air coming on?

Also, the solder on these connections (on the box) looks brown/orange, is it possible that the CCM just has bad connections?

Attached Thumbnails

       

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'83 300SD, 220k.

I don't have an ETM for the SD so can't be of service there. The brown/orange on the PC board is probably rosin left over from the soldering process when the unit was built and is not a problem. Mercedes did have problems, not recognized for many years, with cold solder joints in some of the connections. The cruise control electronics in particular have this problem and the climate control perhaps also. A cold solder joint will appear as cracks in the solder or an obvious (perhaps with a magnifying glass) disconnect between the PC board and the wire at that spot. It is possible to repair a cold solder joint by simply resoldering it. You will want to know what you're doing as overheating can do more harm than help. Additionally, some commercial rebuilders won't accept (as a core) your unit if it has been worked on by someone else.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Hopefully these will help. I had to create individual files to keep it under the limit.

Attached Files

	83 SD AC_1.pdf (287.9 KB, 1380 views)
	83 SD AC_2.pdf (601.6 KB, 1009 views)
	83 SD AC_3.pdf (158.3 KB, 769 views)
	83 SD AC_4.pdf (441.1 KB, 747 views)
	83 SD AC_5.pdf (249.7 KB, 826 views)

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K

Use at your own risk. It looks about right based on colors.

Look here about half way done. With a 12 pin connector, you're probably an "early model 126" Middle-aged Mercedes Electrical Repairs

You're probably looking at connector 2.

1 bk/vi temp dial
2 br grd
3 bk/wt ref
4 bk/bu/yl monovalve ctrl
5 bk/gn/wt blower
6 bk/yl/rd center flap
7 br/bu ctr flap switch valve
8 yl/gn fan speed
9 br/wt cold engine lockout
10 bk/rd/vi aux pump
11 bu/vi foot flap switch valve
12 rd/yl + bk/rd pwr +ctr switch valve

For future reference, 9 was br/bl, but everything else was great, Thanks everyone for the diagrams. I'm testing voltage and going to try the 12 12 8 jump!

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'83 300SD, 220k.

After jumping 12->12 and ground, I received full blast air from the driver side vent only. Trying to figure out how to jump the compressor!

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'83 300SD, 220k.

I'd write as br/bk for consistency - and as shown on the second pdf for the SD. bl could be interpreted as blue or black. 7 is br/bu, right next to 9, so it could be easy to confuse br/bu with br/bl with br/bk.

I pulled the colors from the W123 chart, hence the warning.

The Unit seems to not work at all, but I don't have a multimeter to check if the pins are actually bombing anywhere.

Other than that, the 6-12 for the compressor did not make it click on. The PO said the clutch clicked when he wired it to the battery.

I can only assume the K relay is dead at this point. What's the best way to prove that is true?

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'83 300SD, 220k.

That's a premature assumption. Did you also check the middle aged link? From the troubleshooting:

Finally, the AC compressor output can be tested. X1 pin 6 may be fed power by a jumper (X2 pin 12 is handy) to force the compressor on when the engine is running. If it doesn't go on you may have a Klima relay problem, a problem with the refrigerant pressure switch (or insufficient refrigerant), or a bad AC compressor clutch.

Three possibilities listed there, and those are back up by the diagram in pdf #3. Check that to verify the path for the clutch to engage.

Don't trust a PO when it comes to A/C. We all know they just need a little freon...

The clutch may/may not be good. You could jumper the low pressure switch, then re-try putting power to pin 6 when the ignition is set to RUN. If that works, then maybe the Klima (if your SD has one) or the Evap Temp switch is OK, and the clutch at least engages but you're low on refrigerant. If not, it might be the clutch relay, one or both fuses, or the clutch, or the Klima/Evap sensor.

With the low pressure still jumpered, you'd need to get +12 to the relay to test that, or jumper the switched sections of the relay plug to test the compressor.

If it were me, I'd get to Harbor Freight and get a cheapy (<$10) multimeter. It'd save a lot of jumpering and guessing and messing with the system.

If your compressor clutch will pull-in with battery 12 volts and ground applied, and yet there's a no-op situation with all other obvious potential failure points in the circuit being OK, check the following out-of-sight item.

There is a temperature sensitive switch in the compressor circuit that's mounted on the outside of the evaporator case, above and to the right of the throttle pedal. It has two wires connected to it and is often covered with a layer of sticky fiber insulation. The switch has a capillary tube of sorts coming out of one side that extends into the case and contacts the evaporator fins to sense the coil temperature.

The switch's purpose is to open the 12 volt circuit to the compressor clutch coil when the evaporator temperature drops below about 34 to 35 degrees, to prevent freeze-up during humid or rainy weather. The contacts in this switch should be closed above evaporator temps. of about 36 degrees.

This switch will sometimes fail in the open position. To check it, just jumper the two wires together and see if the compressor clutch then pulls in. This switch failed in the open position on my '84 300SD and I used much time looking for the open before I found this temperature sensing switch.

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Respect, protect, and maintain complex systems - whether natural or of German design, to benefit from their full potential.

1982 300SD W126.120 with an OM617.950 from a W116.120
1984 300SD W126.120 with an OM617.951

Sounds like I have an exciting morning ahead of me. Texas heat was unbearable last year in a 95 black untinted bmw. I do not want to relive that experience.

I would just jump 12 12 8 and make a fuse switch from the compressor to the battery to the dash or glovebox... but I actually want something that will last over a month and not burn up 1-2k in equipment, haha.

Thanks again for all the help. I could not find my passenger door vacuum leak. Not really that important anyways.

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'83 300SD, 220k.

Look at the 4th picture of the printed circuit board. Lower left, I believe I see a burned trace. It can be repaired by soldering one strand of wire from a piece of insulated 14 to 16 gauge wire making sure it doesn't touch any thing else except the 2 ends. A good place to start before spending hours looking for other problems.

Paul

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84 500 SEL (307,xxx miles)

Good eyes, Paul, I agree, looks like a burned trace near the lower left hole in the board.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

After soldering the wire, full functionality was returned to the CCM.

I noticed the middle vents had no air out of them on every setting. The defrost and side vents always blew air no matter what (for the most part)

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'83 300SD, 220k.

Think this would work for a later model W126 like my 350SDL?

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Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6