Air Conditioning

My 450SE was still running the original Frigidaire A6 compressor.  It had a leak from the back.  The original Frigidaire went out of production in 2024, so simply buying a new one wasn’t an option.

A friend with a 1973 450SE in Melbourne was in the same boat, so we had been comparing notes.  Since some of these compressors apparently require some modification to fit on the car, we hoped to buy locally so we could test fit and make sure it would actually work on the W116.  He has a trade account with Cooldrive and a few others wholesalers, so at first tried to get a compressor from there.

After months of nothing turning up despite being told they were on the way, we decided we would just have to source something ourselves.   Based on some research, I came up with the following options:

1. Have the A6 rebuilt.  This is possible, but not something I wanted to do. I’ve never had good success with rebuilt AC compressors. There are people around who can still do it, as that compressor was widely used. However, given the cost of fitting, the need for a new drier, regas and so on, I think this is a false economy.
2. Buy a rebuilt four seasons A6.  These are the most commonly available compressor to buy. They are not new, but a rebuilt version by four seasons. They have a pretty terrible reputation. I would think that option 1 is better than this one. You’ll find this on all the sites like FCP Euro, pelican parts and so on.
3. Buy the AKS-DASIS compressor.  I don’t know much about this one. Its made in China and I really couldn’t find any information about people using it successfully. So I don’t know if its any good.
4. Buy a PRO6TEN.  I’ve seen quite a few good reviews of people using this one, and I seriously considered it. Those reviews were not on Mercedes-Benz and so I wasn’t 100% sure it would be a drop in replacement. Its a new modern compressor in an aluminum body and its more efficient and much lighter than the old A6.
5. Buy an S6 Compressor.  Similar concept the PRO6TEN, but a different supplier. I found less reviews on this, but the vendor specifically mentions it for the Mercedes W116 and I’ve bought from them before and know they stand behind their products.
6. Modify the AC hoses and get a custom bracket to fit a Sanden.   I didn’t really investigate this very much, but it is an option.

I went with option 5, and ordered the S6.  Postage wasn’t cheap, but it was still decently priced landed here in Australia.  On arrival, I was pretty impressed with how it looked.  It is made by Sunair in Malaysia, and the part number is CO-5004CA.   The construction of the housing and the packaging seemed high quality.  It was made earlier this year, so hadn’t been sitting on the shelf for years too.

Next I needed a new receiver drier and I found a proper one overseas and had it shipped. I also got a new pressure switch.  The previous owner reported the AC had been very cold about two years ago, I figured that was probably all I needed.

I had the compressor fitted locally, and the good news is that the S6 fitted well.  There were no modifications required.  The bad news is that on the 450 engine, there is this quite elaborate manifold that connects the AC hoses at the top of the engine down to the compressor at the bottom.  Mine had cracked and the system would not hold vacuum.  I called around, and MB Classic in Greenacre had a 450 engine just removed from a wreck.  I was able to buy a manifold.  With the days counting down, I drove over to get it right away.

With the new manifold fitted, I no longer had a big leak, but I had another problem.  The system would not circulate freon properly.  It looked like the expansion valve may be blocked.  To make sure I got another in time, I drove the old one over to Cooldrive in Alexandria, and we matched it with a generic one they had.  They had stock in Melbourne, but it would take two days to arrive.

The days were counting down, As I drove over to pick up the new expansion valve, it was now Thursday and I was to leave on Tuesday.  That gave two business days to get the system sorted out.  The new expansion valve was fitted friday, however, there was still a blockage in the system.  The Mechanic left some kind of cleaner in the system over the weekend, hoping that would sort out the issue.

Luckily, that seemed to work, and Monday morning, he was able to remove it, and the system circulated properly and didn’t have any leaks.  On further examination, we think the cause may have been the old receiver drier breaking down when it was used a couple of years ago.  There is a sort of filter on the inlet of the old A6, and it was full of black debris.  The port to the drier seemed to have this also.  I guess the cleaning solution got a lot of this out of the evaporator.   That should have been ok, but as the system was finally gassed up properly, the gas bottle ran out.  We only had about half a charge in the system.

I called around and managed to get a favour from another Mechanic to fit me in the first thing the next morning.  The system originally had 1kg of R12 when new.  The gas bottle ran out with 450g of R134A, so the cooling performance was pretty tepid.  With 900g, it was icy cold.  I finally had working AC on the morning I was to leave for the trip.  It had been an ordeal, but it was now working.

Ignition Switch

In the last few months, two times when I had tried to start the 450SE, the key did nothing at all.  Normally I would wait and do more troubleshooting, but since the instrument cluster had to come out of the car anyway, I got a new ignition switch as a precaution.  I figured it was the most likely cause.

Instrument Cluster Lighting

Another small last minute problem was the instrument cluster lighting.  This had stopped working.  While the cluster was out, I had the rheostat bypassed.  No time to get another and I only use it on full brightness.

Oil Change

The 450SE had about 4,000km since its last oil change.  I normally do mine at 5,000km or 2 years, whichever comes sooner.  Since the trip was another 4,200km, I did a quick oil change the night before, after picking up the car from the AC being repaired and before the final regas the next morning.

Speedometer Cable

The instrument cluster had to come out a few times with all the AC work.  One of those times, the cable must have been kinked.  Driving the car home after doing the oil change, it snapped.  There was no time for a repair, and I still wanted to take the 450SE.

I had Claude AI build me an app for my old iPhone to track the odometer and show a big speedometer correctly.  It worked quite well.  This allowed me to make sure I track the distance properly, and know my speed.  I put in a second mobile phone holder.  At some point in the future, I will have to advance the odometer to correct it.

Rally magnets and Spares

And of course, the final thing to do was put on the Rally magnets and pack the box of spares I had prepared.  I had:

• Full set of belts
• Voltage regulator
• Fuel pump
• Battery jump box
• Tyre pump
• Spare fuses, relays, wires, connectors
• SLS control rod
• Oil, coolant, transmission fluid, SLS fluid, glass cleaner, quick detailer, funnel
• Tools, first aid kit
• 6 x 500ml drinking water
• Cable ties, tape etc.
• Nitrite gloves
• Old towels and rags
• Head torch
• Power probe
• Spare fuel hose etc

The post Preparing my 450SE for the Bay to Birdwood trip appeared first on Classic Jalopy.

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.

The post W123 air conditioning upgrade appeared first on Classic Jalopy.

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.

The post Uprated W126 A/C condenser appeared first on Classic Jalopy.

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.

The post W126 A/C almost blowing cold appeared first on Classic Jalopy.