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  1. #1
    FEP Power Member Broncojunkie's Avatar
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    Default AC systems for early fox

    My 79 cobra (auto v- is pretty much all original. I've pulled the motor and currently in the process of building a roller motor. While it's out, I'll be painting the engine bay and doing some upgrades.

    The ac system was complete and still has pressure in it (still in car). I was hoping to try reusing the compressor, flushing the evaporater, and replacing the lines and condenser. It looks like parts are scarce and expensive. I'm not sure if I should stick with the old system or try and find parts from a newer fox. I'm not even sure that's possible, but I'd like any advice I can get. I'll be converting to the new refrigerant, of course, but I would like to have a system where parts are more readily available/cheaper. My other cars have had ac removed so it will be nice to have at least one old fox with working ac!

  2. #2
    FEP Power Member dagenham's Avatar
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    If you're not concerned about originality then I would go with newer fox parts. But, if the system is holding and has no leaks why mess with it at all.
    If your just worried about the hoses you can have new ones made probably at half the cost of buying them new from most parts stores.

  3. #3
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by Broncojunkie View Post
    My 79 cobra (auto v- is pretty much all original. I've pulled the motor and currently in the process of building a roller motor. While it's out, I'll be painting the engine bay and doing some upgrades.

    The ac system was complete and still has pressure in it (still in car). I was hoping to try reusing the compressor, flushing the evaporater, and replacing the lines and condenser. It looks like parts are scarce and expensive. I'm not sure if I should stick with the old system or try and find parts from a newer fox. I'm not even sure that's possible, but I'd like any advice I can get. I'll be converting to the new refrigerant, of course, but I would like to have a system where parts are more readily available/cheaper. My other cars have had ac removed so it will be nice to have at least one old fox with working ac!
    I'm not sure I trust the 40 yr old lines and condenser. I know I can have some new hoses made at a local shop but any idea if a condenser can be recored like a radiator? Cheapest one I found was $275. Or maybe I can retrofit a newer one? Basically, that's why I was thinking of just updating the entire system. But I'm also not sure if the evaporator has the same connection.

  4. #4
    FEP Power Member Broncojunkie's Avatar
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    I may just suck it up and buy the oem style condenser. These ol cars are getting hard on the wallet lol

  5. #5
    FEP Member kingsnake's Avatar
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    I have a 79 cobra and am in the process of redoing my AC as well.
    I have researched this extensively and had many discussions with the guys at classic auto air about this.
    I don't know of any place that has oem style parts for a 79.
    The guys at CAA claim new condensors and OEM style lines are not available.
    I was originally hoping to go R12 myself, because I have 10 cases of 1lb cans of the stuff.
    After research, I now plan to convert my system to R134a.
    R12 systems and R134a systems use different oils that are not compatible with each other.
    Every part of your AC system needs to be removed and flushed with lacquer thinner when converting to 134 to remove the old oil.
    This means removing your dash and removing the evaporator.
    I cannot emphasize this enough. Also, a new receiver drier is a must.
    R 134a systems need a different style condenser to operate at peak efficiency.
    CAA will make one that fits your car if you send them dimensions and a pic of your OEM condenser.
    I think a receiver drier and 134a condenser cost about $350 from CAA.
    Remember that the old York R12 compressors were not designed to run above 5500 RPMs
    They take a lot of HP to run, compared to newer 134a units.
    Consider a new 134a style compressor, I purchased one new from Rock auto for $110.
    These old cars being hard on the wallet is a freak n understatement at best!
    No matter what way you go, I applaud you for keeping your AC working.
    Not many guys do. It makes for a much better summer time cruiser.
    Good luck with your project.

    Kirk

  6. #6

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    I like my conversion kit I got from LMR (made by Hose Wizards). It has an R-134 optimized condenser and compressor, as well as all new lines. It takes the guesswork out of things and works great! I installed it having removed EVERYTHING from my car years ago.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
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  7. #7
    FEP Super Member erratic50's Avatar
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    Lots of good info above.

    One other major difference R12 vs R134a I didn't see listed above is the pressure switch.

    As a matter of fact, a R12 system charged with R134 and a compatible oil and no pressure switch change will last a long time. High RPM applications are best addressed by making sure the WOT switch cuts the AC clutch and you only run high R's at WOT.

    You could use an underdrive pulley on the crank to also slow down the belt speed at the AC.

  8. #8
    FEP Power Member Broncojunkie's Avatar
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    I would think you could flush the evaporator with it still in the car. Wasn't planning on pulling the dash, but I'm sure it wouldn't hurt to change the heater core anyway.

  9. #9
    FEP Power Member Broncojunkie's Avatar
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    Looks like I need to go back to the drawing board and see what my best route is for upgrading to a newer system. I do happen to have a compressor from a mid 90's f150 lying around (just pulled from a low mileage motor). I think ford switched to r134a in 94? Lines and condenser shouldn't be a problem.

  10. #10
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    I did an in car flush on an evaporator on a car that had a seized compressor and it was fine. Just take your time and flush it in both directions and make sure you blow it out very thoroughly. I used this stuff and it did not leave any residue behind. https://www.amazon.com/Johnsens-6544.../dp/B001DKNLJI I just used one of those rental flush kits from AutoZone. I did use most of the gallon, but again the compressor had seized so there was a fair amount of crap in the system.

    I believe Ford did switch to R-134a in '94 which is unfortunate, but it looks like the compressor used in the later fox Mustangs was used for R-134a applications so you should be in good shape. Do you think a later fox condenser would bolt right in on your car? Only other thing would be to make sure the desiccant in the receiver drier is compatible with R-134a. I believe most made these days for cars originally designed for R-12 are compatible with both.
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  11. #11
    FEP Super Member erratic50's Avatar
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    A good conversion oil is compatible so flushing simply is not needed.

    The R12 to R134a converted AC in my 89 blew 52 degree air for 9 years and worked great when I sold the car.

    The R12 to R134a converted AC in my 86GT blew 54 degree air for 10 years and worked great until the pressure hose started leaking.

    A few things to note.... a proper and correct evacuation was not done. The old timers born back in the early 1900’s talked about how “evacuation” was done in the early years of refrigeration. They would keep the compressor off and open the high pressure valve then connect to the low pressure side. They would ideally work on a very cold day when the relative humidity was near zero. They would put refrigerant in until it displaced all of the air and just starts coming out the other end. A “displacement evacuation”. Well the old timers talked about how vacuum pumps would leave all kinds of air behind and the systems didn’t work as well, etc. It pays to listen to old guys sometimes I guess.

    Anyway I filled both systems until the pressures were where they should be. The 86 was lower because the compressor was very high mileage - over 200K miles at the time and it was a hot humid day when I fixed it. But it worked great- like new.

    One word of advise - the slip together lines are notorious for destroying O rings and losing charge. NAPA sells a condenser that uses 3 O rings rather than 2. They sell a clamp that goes over the spring fitting and holds both ends of the line so the joint doesn’t move.

    The 3 O ring thing isn’t mandatory but helps. The clamps are the secret to keeping a working AC for a lot of miles in a foxbody.
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    Last edited by erratic50; 03-19-2018 at 01:01 AM.

  12. #12
    FEP Power Member Broncojunkie's Avatar
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    Great info guys!

    Erratic,
    Is the NAPA condenser a mustang-specific part?

  13. #13
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    I guess my thought on flushing the evaporator is you are pretty much replacing everything else. While the system works fine now I'd rather just make sure the evaporator is clean if nothing else for peace of mind. It isn't that hard and doesn't take that long to do.

    I've heard of the displacement evacuation method before, but I've never tried it. I use an ancient Robinaire vacuum pump that I inherited from my grandfather and I've never had any come-backs on any A/C work I've ever done for anyone.
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  14. #14

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    Interesting thread here. I have a 79 Capri 5.0 still with the original R12 ac in it. I has not worked well for 20 years. I have not seen a replacement six rib clutch for the York style compressor in a parts store, ever. Mine seems to ice up after a few minutes of highway driving. The combination valve, ie, expansion valve, suction throttle valve system parts are also not available.

    Anyway, when it comes out of retirement, it will get a 134 system base on an 85 setup.

  15. #15

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    Check out red tek r12a... Might help a little.

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