The A/C worked well until I took the car off the road for a couple of months to fix the fuel system.  After that, the freon had leaked out again.  A further re-gas and having the valves changed basically just gave me my road trip to Brisbane.  Clearly there was a leak somewhere.

I looked with my blacklight, and the issue was apparent.   There was green dye all over the compressor.   This isn’t all that surprising.  A/C compressors need to be run regularly to prevent leaks.  As my car was likely laid up for a while before my ownership, the seals had obviously gone.

My 240D is new enough that it uses the GM ‘pancake’ style rotary compressor, not the York.  My 240D still had the AC Delco compressor with metric fittings these cars came with.  I do not believe these are available anymore.  I bought an Omega brand compressor to replace it with.  Naturally I had the drier replaced at the same time.

I could have stopped there but decided to upgrade the condenser too.   The original condensers designed for R12 don’t work all that well with R134A.   I’ve been very happy with the Klima Design works condensers in my 560SEC and 450SLC so decided to also put one in the 240D.

I noticed in the W123 instructions it mentions that you can paint the condenser black to match the factory look. I reached out to Klima Design Works to confirm that this would not impact cooling performance.   Their reply indicated that their testing hadn’t seen any measurable impact.  I decided to paint mine before I had it fitted.

It was a pretty easy job to paint both the condenser plus the various fittings satin black.  I only painted the front of the condenser.    The back is not visible.

I had the new compressor, condenser, drier etc fitted a couple of weeks ago.   Painting it black made a huge difference in how noticeable it is.   I’ll probably go back and see how much I can paint the condensers I have in the two 126s and the 107.

Its been pretty cold in Sydney since I got the car back.   The new upgraded A/C seems very good, but I’ve not had a hot day to test it with.  I’ll be doing a trip in January for the 50 years of the W123 event, so having nice cold A/C will be a plus for that event.   While I don’t miss most of the features of modern cars, I do very much appreciate cold A/C and these condensers really help.  I won’t know until it gets hotter, but so far I am happy with my W123 air conditioning upgrade.

While I don’t particularly notice it when driving, it is apparent when the compressor kicks on when the car is idling.   The compressor is probably using a decent chunk of the power the OM616 makes at idle.

It is a complete bolt in kit so I could go back to original at any time.  I don’t plan to though. I have kept the original one to go with the car.

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While I had to do a few things to the climate control system, the A/C worked pretty well after being charged up.   The main issue was a leak from the compressor.   For a while, I was able to get away with charging it up annually, but recently it was degrading pretty quickly only a couple of months after a charge.    It was obvious that the leak was coming from there by using a blacklight.

Since I was already having the compressor changed out, I also thought this was an opportunity to try and upgrade I had been considering for a while.   Klima Design Works offer an uprated W126 A/C condenser that is designed for R134A.   R134A is not as efficient as R12, and this uprated W126 A/C condenser is billed as 30% more efficient than the stock unit.    That help restore the A/C performance lost through R134A.

I did some research on the various US forums and found good feedback from W126 owners in climates like Texas and Florida.   Basically the consensus seemed to be to either use R12, or this upgrade.   The upgraded W126 A/C condenser comes with the requisite brackets and hoses to interface with the W126 A/C system.   They offer two types depending on year and model.

Obviously, since I was having the compressor changed as well, I supplied a new receiver drier and TX valve to be installed alongside the compressor.   Like with my 300SE, I went with a brand new Denso compressor.   I’ve not had a lot of luck with rebuilt A/C compressors in the past, and given the high labour cost to have it installed, its much better to go with new.

While the car was in the shop, the front brakes were attended to.   On a recent brake pad change, I noticed that one piston on the front drivers side was not moving at all.   I ordered the rebuild kits, plus pads and a new set of front rotors.   My rotors were pretty crusty and within 2mm of the wear limit.   A good time to change them.   The rebuild kits were advertised as Bendix, but my mechanic later told me they were actually ATE units.   This was really annoying as I paid quite a bit more for these kits.

In doing the install, my mechanic told me that the fit of the uprated W126 A/C condenser was really tight.   This probably added a bit to the cost, but in my mind is a good thing as its using all available space for cooling performance.     There was also a little bit of interference between the secondary air snorkel on the 560.

The other issue he ran into during the install was the missing aux fan guard caused a rag to get sucked into the fan and damage it.   This was a problem with the Meyle auxiliary fan I installed a couple of years ago.   Since then, they moved to an improved design that does fit the fan guard.  I have that one on my 560SEL.   I’ve ordered one of these fans to fit to the car.

So far the weather has not been hot enough to really test out this upgrade.   We’ve had one day where it was about 25c and fairly humid and the A/C worked very well.   Better than before.   However, It was previously able to handle days like that.   The real test is when the temperature gets up into the high 30s and humid.

I’ll use this summer to see how I go.  If I’m really happy, I’ll also fit this uprated W126 A/C condenser to my 560SEL.   On really hot days the A/C performance is sub par.  A new TX valve would improve things I am sure.  However if this upgrade works really well, I may do it too.

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I went through the entire climate control system of the car as part of my troubleshooting.   I found that the car had a missing aspirator fan, a very noisy blower motor, and an intermittent climate control unit.   These were all changed.   The next step was to take the car to my mechanic to fit the new compressor and receiver/drier.  During the disassembly he noticed that the large A/C hose was slightly weeping.  Changing this hose means removing the compressor, so now was the time to do it.   Of course, it is not your regular A/C hose.  It also functions as a way of cooling the petrol going into the fuel distributor.

The hose was sent off to be repaired, as purchasing this hose new from Mercedes-Benz would probably require giving up your first born child.  This involved leveraging the fittings with new A/C hose.    Interestingly enough, while the hose was being rebuilt, I was driving the car around without this cooling function and didn’t notice any adverse effects.

Sourcing the A/C compressor was not as simple as you might think.   The electronic parts catalog calls for part number A0002302411 for cars equipped with self-leveling rear suspension.  As an Australian delivered car, mine is so equipped.   This translates to a Denso 10P15C.    Cars without self-leveling rear suspension require A0002301111 which is a Denso 10PA17C.  These compressors do not look alike, to the point where it looks unlikely that the wrong compressor would fit without modification.   The 10PA17C is cheaper than the 10P15C.

Today, the new compressor was fitted, along with the new receiver/drier and the car gassed up and ready to go.   When the compressor clutch went out, it shorted out the Klima relay, so this is the final thing that must be replaced.   The A/C does work when the relay is jumped.

At the same time, I had been smelling petrol when starting the car.  Turns out the fuel pressure regulator was faulty and was squirting extra fuel on startup.   Apparently to stop petrol leaking out, this goes into the intake.   Changing the regulator is likely to improve the fuel economy of the car.

This has been a rather expensive exercise, but so long as I am not hit by an inattentive SUV driver, I should have a reliable W126 daily driver for the long term.   Some of the most likely potential problems have now been sorted out.  This includes rebuilding the climate control, new water pump, head gasket etc.

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