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Old Vehicle, Old A/C system

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  • Old Vehicle, Old A/C system

    My 15 year old son and I bought him a very used 1976 Monte Carlo that we have started working on together to do a possible conservative restore.
    From underneath the hood to the interior and maybe paint some day. The car runs fine but it does not cool and realized the compressor belt is missing which I assume that the compressor might be out of commission. We decided after pulling the leaky original radiator that we need to inspect or replace many of the original mechanical parts under the hood, i.e. water pump, fuel pump, alternator, leaky power steering pump, etc. After removing the condensor, the a/c lines, getting into the heater box on the firewall and disassembling the evaporator and blower motor. From there moving inside and removing the air mixer (or whatever it is called) under the dash. This is what I found: the condensor in front of the radiator seems to be okay? I pressurized up go 60 PSI under water and did not find any leaks, I did the same on the evaporator and no leaks (not sure if this is recommended). I am sure the hoses probably need to replaced and o-rings to convert to R134a, I assume a new drier too? Where should I turn from there without spending a ton of money on a vintage air conversion kit?
    Should I buy a rebuilt compressor or a new sanden compressor?
    Can i use the original condensor?
    Can I use the original evaporator?
    I assume I should replace the lines?
    Should I shell out $1500 for a conversion kit (which I really don't want to do)?
    My goal would be to take it to a professional to get everything re-charged, we would like to do anything we can ourselves for the experience and to save money.
    Thanks for the help! Phil

  • #2
    Take a long hard look at the condenser. The can not leak, but still be bad. If there is any corrosion between the tubes and fins, it will not conduct the heat away from the tubes.
    The good news is: generic replacement condensers are not expensive and do a better job getting the heat out of the refrigerant. This is especially important when changing over to 134a. With a generic replacement, you'll need new hoses made up but it is worth it in the end.
    You need to be very sure no moisture remains in the components you tested in a water bath.
    I believe your car should have an A-6 Frigidaire compressor. One of the best made I run 3 of them. Good used one are better than some of the "rebuilt" ones on the market. You'll need to drain all the oil out and replace with 10 oz of PAG 150. Some A-6 clutches are getting scarce esp the double groove ones. There are some special tools required to remove and replace the clutch.
    For my money the A-6 beats all the others, but there are some new ones made to be a bolt in replacement for the A-6 and there are some adaptor brackets made to fit a Sanden in place of the A-6.
    If your compressor turns by hand and the clutch looks good, I'd drain, and re fill with PAG oil and use it.
    As to the receiver, from what I can find online, it jibes with my memory that it would have a VIR system, where the Tx valve is contained within the receiver itself. Those can be tricky to work on, but new descant bags are available.
    Unless you plan on buying a whole lot of special tools, you might be better off paying a shop to get the A/C done.
    I only do my own (semi trucks) but have invested a ton of money in hose crimper, vacuum pump, A-6 clutch tools and OEM "Kent Moore" rebuilding fixture. That doesn't even cover the normal A/C tooling.
    If you rebuild an A-6 the correct way (it has some "select fit" parts) and don't run it low on oil, it will outlast the car. A cheapo "rebuilt" A-6 I bought didn't last 2 seasons, and when I pulled it apart, I found out why, It was literally thrown together and parts epoxied in place!


    • #3
      Thank you Cornbinder, you know your stuff, if you don't mind, see attached pictures and let me know what you think about the condensor? Thanks, Phil


      • #4
        I really can't tell much from pictures, I did notice that some of the fins seamed to have come loose from the tubes at the bottom. Look really carefully where the fins are pressed on the tubes, If you see white (powderish stuff), it is likely aluminum oxide which will impede the heat transfer. Grab a magnifying glass and look close at the tube to fin joint. I would look at some generic paralle flow condensers for the highest capacity in about the same size as what you have now, Make up some brackets to mount in place of the old tube and fin condenser.
        That is an A-6 compressor with the very common 5 or 4 7/8" clutch. Grab the rubber damper on the front of the clutch and see if it will turn?
        The receiver is the VIR type and you can get a new descant bag for the bottom chamber if the valves in the top are ok.
        I'd scrap the hoses and start over with either the new Burg-clip style or crimp lock on barrier type hose. The old R 12 hose will not stand up to the smaller molecule size of R134a nor the higher pressure. You'll need a GM pad fitting for the compressor end, but these are made in a verity of configurations, and adapt the compressor to O ring fittings.
        You'll need a good mobile A/C supply house to supply what you"ll need. MEI/Air source, Red dot or (defiantly second tier) Santech can supply the fittings and hoses. You'll get nowhere trying to source stuff from a local autoparts store like NAPA or Orilley's Look in the yellow pages for truck refrigeration or names like Thermo-king or Carrier.
        Again, if this is a one and done project, you'll likely be money ahead paying someone to do the work, The new hose and fitting style ( Berg clip, frigolia etc) are not cheap and neither is a hose crimper for the beadlock fittings if you go that route, either way it is a fair bit of money.
        When I build an A/C system for one of my old trucks, I start with the evaporator and Tx valve and build the rest of the system from scratch from those two parts. I get a cast bracket to hold the A-6 and run all new components and hoses. I keep a fair inventory of fittings and spec driers that fit my needs for size and fittings. I keep a fair amount of hose in stock in 4 sizes to make up what ever I might need. I wire my own safety and fan systems (switches) I have a list of OEM parts for things like the GM pad to O ring manifold and bracketry to mount A-6 to a Cummins diesel as well as sources to get those (obsolete) OEM parts. I guess what I'm trying to say is unless you have a real need to do it yourself, it is going to be more expensive to do just one vehicle than a good shop will charge.


        • #5
          Thanks Cornbinder, I appreciate your help, I will get a professional to fix me up. One last thing, do you think it is okay to put back together the evaporator, evaporator box, heater core, and heater / a/c box under dash before I take the vehicle in?


          • #6
            Yeah, if you got all the moisture out of the inside (if any got in) the evaporator, then I would button it back up.