Ressurecting the Air Conditioning

[randall977]

I'd like to get the air conditioning working on my 85 M6 and have started down what could be a long and expensive road.

So far I have taken the whole system apart and have replacements for the dryer, pressure switch, flexible hose pipe sections to R134a, all pipe seals (also R134a) and expansion valve. I believe the condenser, evaporator and compressor are / were in good working order. So it's a simple case of putting it all back together and gassing it up...or is it?

Well, there will certainly be some debris in the metal pipes I am going to reuse, possibly the condenser and evaporator too - this could ruin all my work. I plan to get an air compressor, flush gun and air con cleaning fluid to flush the system through.

Has anyone done this? Can the condenser and evaporator be successfully flushed? - One YouTube video says it doesn't work on modern cars...but this isn't a modern car - the ducts etc are larger?

[randall977]

I've made quite a bit of progress over the last week. I took out all the old a/c equipment, flushed the pipes and condenser for reuse, flushed and cleaned and dried all the parts. I inspected the compressor, replaced the faulty fan control switch, re-wrapped the insulated pipes, reinstalled everything including the new r134a flexi-pipes, seals and dryer (I think this is basically the upgrade kit). 200cc of PAG100 oil was added to the compressor and now all I need to do is re-gas and see what happens...

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[TBM]

Hey Randall,

I don't know if you want to keep everything original?

I know that if you go to a quite common and cheap parallel flow condenser you are making huge progress.. Also, convert to a Spall high flow push fan to move much more air.. The old fan is very weak. The Evap and all its components you've taken care of so that's all is good as it seems.

I personally am going to spend some dough and go with: http://classicretrofit.com/
They are in blighty and can help a lot even if you don't buy their system, they might have some really good pointers as to whatever gives you the most bang for you upgrade dollars since they spent so much time trying to upgrade 911 shitty A/C. BTW the new RUF uses their system as well as some other well know Porsche upgrading firms.
Another resource that I have found that may be really helpful is these guys: https://www.macsw.org/web/Online/Resour ... _Resources
They have a blog and forum, they are willing to help solve issues.

Also, I would insulate the hose coming off of the compressor traveling along side of the inner fender. There are really good refracting sleeves that can help a lot. IF you are inclined, as a matter of also helping performance, coat the headers that live on that's side with Ceramic insulating coatings. It will help in evacuating the exhaust by keeping gas velocity way up as well as lower the under hood temp by a huge amount. As much as 90-100 deg F.

[randall977]

Thanks TBM, really useful advice and interesting links - especially the electric a/c - I guess that will be the future of air con. I've used a company before called Fen Air https://www.fenair.co.uk for an early 60's Quattreporte - the fan on that car was like something off an ice cream fridge...and I think it was! I sent them the old stuff and they rebuilt it to new standards to be reinstalled.

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Being in the UK a/c is not essential for much of the year so I'm happy with a system which works, it doesn't have to be great. I don't like things that don't work and so couldn't live with a non working a/c. I do also like originality...

If I were going to do a lot of driving in it then I'd definitely look to upgrade. If it doesn't work when I re-gas it then I might still upgrade it!

[randall977]

To wrap this one up - my a/c now works - I'm kind of surprised as I thought it might never work - but it does and quite well.

Here's a summary of what I did;

1. My system was missing the dryer, pressure switch and a long section of pre formed pipe.
2. I bought a new dryer, pressure switch and replaced both flexi pipes which go to the compressor for r134A upgraded equivalents. I sourced a replacement pre formed pipe (NLA) from Mr Watts, I replaced all of the O-rings with r134A ones. Total cost was around £350, maybe more.
3. My compressor is a Behr wingcell, looks newish but is original to my 85 M. The condenser is in good condition - new OE maybe.
4. I flushed though the system whilst apart with an a/c aerosol flush kit to remove any debris. I also flushed the condenser which took a very long time to dry - for which I used a shop vac and adapter pipe to blow the flush liquid out. Important: ** Do not flush the condenser as you will probably clog the expansion valve **
4. I put everything back together, replaced the faulty a/c / heater switch on the dash, new belt on the compressor (which can only be done by removing the compressor - why?!?).
5. I took the car to my local ATS for a re-gas but they couldn't attach their machine. Eventually I worked out what adapters to order from eBay - R12 to r134A adapter hoses (about £8 from China) - then they were able to re-gas the system.
6. To begin with the pressure valve leaked so I had to re-do the joint and used some sealant - it is a taper fit. After this it held pressure and was fine. I think ATS must have made a big loss but fair play to them for seeing it through.

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[KINGJOHN808]

Wow!

Great write up. Im in the process of doing the same thing. Have a new drier, expansion valve, new hoses and O-rings. Haven't flushed the evap or condenser yet and awaiting repair of my original compressor. I live in Hawaii so we definitely use AC year round, so I gotta get my ac to work. My 633 is mainly used for "cars and coffee" and far from a daily driver.

Hope my reinstall and repair goes as smooth as yours.

Aloha!

[KINGJOHN808]

I've made quite a bit of progress over the last week. I took out all the old a/c equipment, flushed the pipes and condenser for reuse, flushed and cleaned and dried all the parts. I inspected the compressor, replaced the faulty fan control switch, re-wrapped the insulated pipes, reinstalled everything including the new r134a flexi-pipes, seals and dryer (I think this is basically the upgrade kit). 200cc of PAG100 oil was added to the compressor and now all I need to do is re-gas and see what happens...


AC1.jpg

AC2.jpg

Are those parts from two different cars? Haven't removed my my evaporator yet but looks like two evaporators and two fans? Thanks in advance for the info

[randall977]

I borrowed some spares just in case...

[sharkfan]

Just spotted this thread - well done for resurrecting the system.

One thing to note is to RTFM to get the most effective cooling in the car; all the sliders to the left is the key trick and then direct whatever (and wherever) the cold air comes out; I say wherever as with my late 1982 car the most cold air comes out over the dash (not the windscreen vents, the next ones down) whereas on my 1985 M635 the most cold air comes out of the vents above the HVAC control.

I got lucky with my M635 as it was all intact but hadn't worked for nearly 10 years - I took it to a little old guy in Yorkshire and he converted it to run on R134 and it has only required a little top up every 3 or 4 years since then.

[psdejong]

I just finished mine. Converted to 134A. I installed a new compressor, dryer, parallel flow condensor and new expansion valves. Before I bought this car (1988 M6) 6 months ago, it had been sitting for 8 years. The system was totally dry and the lines all rusty inside. It took a lot of work and de-rusting the inside of all the lines. The whole system had to come apart. All lines removed. Evaporators appeared to be in good shape.
This morning I charged the system up. It had been holding vacuum for over a week.
The sticker on the hood says to charge with 3.69 lbs of R12. I understand that with R134A you need to charge 85% of that, or about 50 ounces.
The system works, but I was a bit disappointed. Having said that, after charging with 53 ounces, the pressures were still under the values shown on the gauges. I had bought a new set from HArbor Freight. So maybe there isn't enough freon in the system. Would he parallel flow condensor require more volume, maybe?
My air temperature coming from the vents, is only about 56 degrees. Compared to my Porsche 928 that is not very low. The 928 blows out 35 degree air.
Looking at a pressure/temperature chart I found on internet, my pressures should be OK.

At 75 degrees ambient this morning, my AC pressures run approx 50 psi low, and 150 psi on the high side. .
Maybe I need to increase the charge even more?