w124 CCU wiring disaster. need pinout or picture
 

today im working on a 1987 300td that had been left in the wrong hands at some point. there was an issue with the klima and or compressor tach pickup so they decided to start cutting wires behind the dash and ran some jumper all the way from being crammed in a pin for the klima to some random toyota relay that was triggered from some of the wires that come off the CCU plugs :eek: the blower had a mind of its on even when the CCU was "off" and the compressor ran only on the "economy" setting so it was just an absolute mess. i am putting it back together as factory and going from there. but while trying to replace a couple of the pins on each of the 2 big plugs that go on the CCU, all the wires decided to leave their spots when i turned my back! this is on the drivers side plug. does anyone have a wiring pinout that has colors stated or a good picture or so of each plug so i can see where these need to go? i would like both plugs if possible because i can tell they have been popped open and i don't trust the last person who touched this. but don't loose your's either trying to get a picture! :D Thank you!

Page 301 is the beginning of CCU diagrams.
Wiring Diagrams

These diagrams are a bit easier to read. Its for 1992 but all the CCU info is the same.
http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1992/300D/SYSTEM%20WIRING%20DIAGRAMS/4100.pdf
http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1992/300D/SYSTEM%20WIRING%20DIAGRAMS/4101.pdf

Good luck.

THANK YOU SO MUCH!!!! :)

Be careful, they changed the climate control in 90 as far as the aux fan control goes. These are all in the "right" connector. The "left" connector is the same across the W124 range.

Pre 90, the CCU gets a binary signal from the head sensor that shuts down AC at excess temperature. Another switch in that same sensor goes to the aux fan relays.

90 and after, the CCU gets an analog signal from a thermistor sensor in the head. It does the overheat decision and also triggers the fan relay.

The wiring diagram you need can be found at w124-zone.com, you'll have to register but it's free.

i will check that out! i went by the 2nd pic tjts1 posted and i think i had 2 wires left over that were different colors but put them in the remaing spots by by the wire length and creases in the wire from the connector "cap". everything seems to work well! i do have some vac leaks to sort though. i bypassed the by using an ice cube relay for testing and found the pin that goes to the compressor clutch is in the wrong spot so ill try to find the colored diagram for that as well.

if anyone was curious what it looked like... this was after the weird relay and all the wires from behind the CCU to the klima relay were cut out. there is more of this kind of stuff the more i dig :(

Derp!

Daaaang. Some people just should not touch controls.

I would seriously look into finding a replacement wiring harness.
Or invest in a good soldering iron, heat shrink, and a heat gun.

Engine bay harness between a 300D and 300TD should be identical.
Dashboard harness should be almost the same.
I wonder if they made the wagon-specific items on a different body harness.

the hvac electrics are working well now after some soldering and heat shrinking any wires that they used a knife to strip the insulation back and probe around until they though they found the compressor turn on signal too the klima relay. poor wagon :( and the funniest part is... i am no the new owner of it! :eek: :D so i am the new owner of an 87 300td! :) i have wanted an SDL since i sold my 300sd awhile back. was very interested in the 603 and was greeted with (drum roll) :musicband a blown HG or cracked head :D. i will be posting a new topic in the diesel discussion about that whole thing and being new to both the the w124 and 603 unexpectedly haha! back on topic to MY wagons wiring :cool: the wiring is plugged in and seems to be working except the fan always seems to be on a very low speed when it should be off. is this normal for constant ventilation or something or do i have something wired wrong? all fan speed settings seem to work. i will test with a few different CCU's. and there is no illumination on any CCU i have tested. i will recheck the connection for that too. everything will be sleeved and tided up once everything works and a crack free dash is installed with rebuilt pods. can i rebuild the pods with the performance analysis ones? how many are there total? the connection that goes inside the box works and the oval one in front works. has anyone just closed off the recirc door with zip ties and done away with it? both pods are shot and the linkage for is all messed up. it such a pain to get to even with the top thing off for the dash vents!

This might be a good time to do the infinitely variable blower fan mod.

Yes the fan always runs at least on low speed unless you push the 0 button.

Chapter 83-600 in the FSM explains it all including the location and function of the vacuum pods.

i saw that awhile back and it is for sure on my to do list! :)

this seems to run on low when the "o" is selected :confused:

My 87 CCU had this problem also. I replaced it with a JY 91 or 92 CCU from a 300e which fixed it. Mine also failed to shut off the AC compressor.

interesting. ill try some more ccu's. so i decided i'm going to remove the hvac box and install a new evap so i won't have to pull the dash again because i find it leaks. also a good chance to clean everything very well! i found 2 beautiful black w124 dashboards but they have the passenger airbag. can this be removed so i can install the glove box liner and door like on the old dash? any other differences in the later dashboards? i love the wood on it too so i'll be finding a glove box door with it if this dash will support it!

I went down the road of trying multiple CCU units on my 87 300D. I ended up following the instructions by forum member James Dean, and was able to replace the capacitors inside the unit. Mine went from flaky operation to perfect operation. I also re-soldered all of the points on the bottom of the circuit board. There is a good chance that flaky-operation could link back to cold solder joints and/or bad capacitors. The boards on these are pretty simple as far as electronics go. I don't have time to look it up right now but if you search CCU solder or something like that I bet you will run across his posts.

good idea. did that to my w123 but i didn't know the w124's had cold solder joint issues.

I couldn't find the thread I was originally thinking of, but this link is a pretty good discussion on the internals and should give you the basic idea of what the W124 CCU internals look like. The capacitors are so cheap there really is no excuse to avoid replacing them while you have it apart if you are checking for cold solder joints. I only suggest this because in my case every CCU unit I tried from the junkyard didn't work properly haha.

any ideas on the dash swap? will it work?