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.

My first step was to see if the system could work.   Overseas readers may not know that in Australia it is illegal to sell freon to the general public.   R12 has not been available for many years.   Therefore, I booked the car into a mechanic who does A/C work to have the system converted and gassed up with R134A.   First steps were quite positive, when the Klima relay was bypassed, the system would blow quite cold if you jiggled the ignition key a little.    That left some obvious repair items though.   I had a new ignition switch (the electrical part) fitted, and ordered a new relay.   I also ordered a rebuild climate control unit.

While the ignition switch was out of the car, I planned to put in a new tumbler.   It used to be possible to purchase these from the Mercedes-Benz classic center.   They would then set them up to use the right key for your car.   The part has been NLA (No Longer Available) for years on the W107, but I purchased it for my 300SE about 18 months ago.   In that time, it is now NLA for the W126 except for the 1990/1991 models.

The new freon had dye inserted, so I was able to check if the system was holding pressure.   In general, it was, but there was a small amount of dye around the compressor.   In particular, between the two halves of the compressor.   The mechanic who gassed up the system had seen success with a product that can be added to the A/C system to seal up minor internal leaks.  We added that component and I waited for the relay and climate control unit to arrive.

The Climate control unit is quite easy to fit.   I have done this job on my 300SE when I was troubleshooting its climate control system.   First, the ashtray is removed, then the radio.   The dash panel can then be pulled down and out to expose the climate control unit.

it is easier to remove the connections to the other switches first.   Care must be taken to keep the fiber optic cable with the switch, so the back lighting will work when it is re-attached.

In the series 2 cars, the climate control unit is screwed into the back of the wood panel, and there are two big connectors that connect the unit into the cars wiring harness.

I am getting quite fast in removing this part of a W126 dash after doing it quite a few times on the 300SE.  Taking the dash apart also allowed me to fix a few other annoyances.   The first was the illumination of the gear selector when the lights are on.   It is a tiny 1.2w bulb that slots into a hole in the underside of the unit at the front.   Not only was my bulb blown, but it had come out and was floating around in the dash.   The second was plugging in the cigarette lighter properly so I could charge my phone.

I had couple of these bulbs in stock, so it was an easy change.   The Ashtray illumination was flickering as well, so I changed that bulb while I was there.   After putting the dash back together, I had a MBCNSW twilight drive to attend.   I had originally planned to take the 250SE, but the weather was rather poor.  Based on this, the 560SEC was the better choice, especially as I could test the Climate Control.

My results were generally positive, but with some more work to be done.  My 560SEC climate control sort of works.   The climate control unit regulated the temperature well, although once or twice it went from cooling to heating.    The new relay worked fine, and I had no problems with the ignition switch.   The three main problems I had were that the A/C just wasn’t all that cold, the centre vents are not working properly, and the electric fan never kicks in for the condenser.  I’m pretty confident that the centre vents will be the vacuum pods under the dash.   That is a job for another time.   As the weather heats up I need to get the electric fan working as the car gets quite hot during prolonged idle.   After coming so far, I also wold like to get the A/C cooler than it is now.

Next step is to take it back to test the freon level, and see if that sealer has worked at all.   I also need to see if the Aux fan will work if plugged into 12v directly.

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