Climate control units interchangeable?
 

Hi-

Does the CC unit from an 82-85 W126 work in a 82-85 W123? The prices for the units are different here on Fastlane, but they look identical.

I want to get one on eBay and there are more options availabe if I can get one from a W126 for my W123.

Thanks!
Aaron

No.

Get one with a part number that starts with 123.

In the long run you are probably better off getting a rebuilt unit anyway. I bought one from these guys:

http://www.gdl-online.com/price6.html

Doh! I got one for my car with a 126 part #. Many part#s that begin with 126 work on the 123s no prob. I guess what I'm asking is why won't it work. What specifically is the reason and what would happen if I were to try to use it.

So despite them looking identical, there is some underlying difference?

I fixed mine last fall by taking it out and resoldering the connections from the board to the connectors. But one of the traces down the middle of the board appeared to be fried. I reconnected it to itself and soldered it, but I suppose there's a reason it fried to begin with. Anyway, since then I can only get full heat on the Defrost setting with Min temperature. The other settings seem to blow tepid on the Min setting, and the blower turns off at all other settings. Der..

I'll try that rebuilder if the eBay thing doesn't work out.

I haven't tried it, but was warned against it...

http://www.peachparts.com/shopforum/diesel-discussion/144313-acc-126-same-acc-123-a.html?highlight=ACC

Nobody seems to have gotten it to work properly, but they may have had other problems. Maybe you could give the final word on the subject?

I'd wait it out on E-bay. I picked up an almost brand new one for $67.

i have an 1983 300sd
 

i have a 1983 300sd and last sept its climate control went out...
so i went to the junk yard... and not knowing any better I pulled one out
of a 1982 300d w123.... and I put it in and it has worked perfectly..
it looked exactly the same as the old one...no difference.. and its still
working fine.... the only thing is i have not finished putting the dash back together.... just lazy:D

Ah, what I meant was:

Yes.

From what I hear, you can! :rolleyes:

But then again, that is swapping the other way around. A 126 into a 123? Still need to hear from d.delano for the final word, I guess.

Haven't installed it yet, but soon will as I need to send 2 CCUs to GDL and one of them is the unit that's still in the car. Got vac pod leaks too so I don't know if I'm the most reliable source to draw from.
CCUs burn out from my understanding due to the aux water pump drawing too much amperage from the CCU. Installing a 1A fuse inline should keep your new CCUs from frying out.

confussion
 

well just so there is no confussion...

I have an 88 300e which i think the body is called a w124...

I have have an 83 300sd and the body is w126...

i went to the junk yard and pulled the climate control from a 83 300d
which is the w123... it fit perfectly...

and I noticed on ebay that there are 2 types of climate controls... 1 which fits the w124 which came later... and one which fits the w123 and w126.

just ask yourself why would mercedes manufacture 2 different climate controls for cars made in the same year.... it is not cost effective... So there interchangeable...

and once the w123 and w126 were stopped they moved to the w124...and the changed it...

So I bet the w123 is just missing a pin on the hook up to the climate control thus deleting that circuit your talking about..

Just to clarify for the original poster, the W123 and W126 units are different parts. I don't know why/if a W123 unit may work in a W126, but I would not assume they are fully interchangeable or that a W126 unit will work in a W123. Also, these units are prone to fail, so there is a fair chance that any unit you find on eBay will be less than fully functional. If you buy a W126 unit and try to install it in a W123, you will be adding another variable. You pay your money and you take your chances.

I got a W126....
 

Climate control module to work in the 123. Fit right in. Don't know if it would work the other way around.

Jeez you can say that again

Panzermann, did all the functions work properlywhen you put that 126 CCU into the 123? The CCUs are cosmetically identical, but I did take the bottom cover off and noticed the traces have different routings.

Seemed to work fine....
 

Only caveat is that the only things I could test were where the air blew out of (which vent) and the heating function, both of which worked, but the a/c on the 300D is still disconnected, so I could not test its ability to activate that.

A comparison of the electrical schematics shows that the W126 unit has an additional relay and connection (C-2/11) for the fresh/recirculated air flap. The W126 has a three-position flap which is controlled by three vacuum actuators via two switches. The W123 unit will not contain this circuit.