Preparing my 450SE for the Bay to Birdwood trip

There was a bit of preparation for my 450SE to embark on the 4,200km trip for the Bay to Birdwood.  The car was running well, but the main thing to sort out was the air-conditioning.  This trip would take us through some pretty hot parts of the country, and I wanted working air to do it.

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