W124 CLIMATE CONTROL UPGRADE

[August Forster]

Here I'd like to open discussion about the crazy project I have in mind. Probably everyone knows that the slot for W124 radio cassette player is identical to R129/W202 automatic climate control unit. The purpose is to install the automatic control unit from R129/W202 in the W124 radio cassette slot and use the the big part of the upper console for installing multimedia command (primarily for navigation purposes). My dilemma is since I have to do the cylinder head work (that's why I have oil/coolant leak which eventually caused loosening of the right side eccentric nut of CA) I may consider instead of repairing my engine cylinder head to swap it with M104 from R129 (there will be no need for cylinder head/gasket work). I'm an amateur enthusiast, but from what I have understood so far from the other threads and by simply looking at pictures of those M104 from R129 that are equipped with automatic climate control system I would need 5 speed AT as well (I just spotted that one of the plague-in socket on the 722.5XX is very much different from my 4 gang 722.369). Or alternatively it is possible to adapt that automatic control system from R129/W202 to W124? May be someone has already done such upgrade and if so, please would you be so kind to share the information about this conversion.
Thank you in advance!

 

[Alphasud40]

I’m confused. What year and model W124 car do you own? What year R129 were you planning to pillage the parts? Here are some things to ponder if you want to install a 722.5 from a R129 with the M104. You will need the R129 shifter, the wire harness, the throttle sensor, a different driveshaft. Also consider you will need a different tail section on the transmission to run your mechanical speedometer and a transmission control unit for a mechanical speedometer car. Finding the driveshaft will be difficult so plan on a driveline shop to make a custom driveshaft. Also the 722.5 transmission is not as reliable as the 722.369 in your car. Bottom line it’s going to be a lot of homework and trial and error.

 

[TerryA]

@August Forster,
Don’t waste your time and $$$ doing this project. There are so many MB intricacies between systems that you will end up tearing your hair out. You would be better off just getting another Benz that meets your needs.

Just my Opinion

lol

 

[dionphaneuf]

I'm also a huge, huge fan of the way the PBU looks on the dash - it's like a vintage 1930s audio unit.

 

[August Forster]

I’m confused. What year and model W124 car do you own? What year R129 were you planning to pillage the parts? Here are some things to ponder if you want to install a 722.5 from a R129 with the M104. You will need the R129 shifter, the wire harness, the throttle sensor, a different driveshaft. Also consider you will need a different tail section on the transmission to run your mechanical speedometer and a transmission control unit for a mechanical speedometer car. Finding the driveshaft will be difficult so plan on a driveline shop to make a custom driveshaft. Also the 722.5 transmission is not as reliable as the 722.369 in your car. Bottom line it’s going to be a lot of homework and trial and error.

Thank you for the response and valuable information!

The W124 car is 1994 E320. Basically, the question whether those R129 with M104 engine with automatic climate control units equipped specifically with 722.6 transmission, which, from my understanding, simply will not fit into W124 chassis, or they (R129/M104 with automatic climate) also have 722.5 transmission which can be mount on W124. Many years ago I owned an E320 Coupe with 5 speed automatic back on the other side of the Atlantic. So, I believe these are the same 722.5s for R129 and W124, or do they differ?

But if this route is way too complicated, is it possible alternatively to adapt the automatic climate control unit from R129/W202 to existing W124 with M104. I've got online the electric diagram of the A/C climate control system for W202 (C280) with automatic climate control module and from what I've figured out from my unprofessional overview the module has wiring with the ECU. Which means there might be an electronic work involving the ECU which I'm very reluctant to go with. What do you think? Where am I wrong?

All the best regards!

 

[gsxr]

The 722.6 transmission will definitely fit in the W124 chassis, but may require some custom fabrication. Lots of people worldwide have done this upgrade, it just is not easy nor cheap.

The 722.5 is ok for 6-cylinder applications only, with stock power output. It's not known for being able to handle higher-power applications, and was never designed for that use.

The 722.6 is far superior in every respect vs the 722.5, btw.

 

[a777fan]

I think I missed the memo… why would a massive project to upgrade the old 124 PBU to the 210 unit also require a trans swap?

 

[August Forster]

I think I missed the memo… why would a massive project to upgrade the old 124 PBU to the 210 unit also require a trans swap?

Considering to swap M104 from R129 instead of due repair of original M104 cylinder head. The R129/W202/W210 auto climate unit wired with ECU, which (I'm assuming) would need the matching transmission. I'm probably wrong in my assumption, but would appreciate a detailed response.

 

[Alphasud40]

The 722.5 is the same unit the W124 car used with one exception. The W124 used a mechanical speedometer and requires a speedo drive on the tail housing. The R129 speedometer is electronic. The 722.5 was a stop gap method of making the 722.3 into a transmission with overdrive for economy reasons. You have to remember in the late 80’s other manufacturers were struggling to do the same and the big 3 in the US did similar things with their tried and true designs. Unfortunately for Mercedes they over engineered a bandaid and as we say 2 wrongs don’t make a right. The 722.6 IMHO is one of the best transmissions out there. My friends have this transmission behind their Mercedes Sprinter motor home with a stage 2 modification moving an overloaded rig with over 100K without failure. The ultimate torture test.

As far as the climate control is concerned it could probably be made to work since the control unit is still stand alone and not part of a can bus from what I can see. However there might be other components in the system which might need to be updated to work with the newer controller such as the vacuum valve block, blower module, and sensors. It would take someone with patience and wiring skills and it would be best to find a donor car to take everything you can think of if you were going to tackle something like that.

 

[Alphasud40]

Don’t think it would matter what transmission you are using I will look again at the diagram to see if speed sensor feed is needed. I looked at a 96 C280 climate control diagram.

 

[Alphasud40]

the transmission variant does not matter.

 

[August Forster]

the transmission variant does not matter.

Thank you!
Very much appreciated!