Another A/C question! '89 K2500 - R12 to R134a

Discussion in 'General Chevy & GM Tech Questions' started by csltrains96, Jul 14, 2012.

  1. csltrains96

    csltrains96 Rockstar 100 Posts

    The A/C system in my '89 K2500 is physically intact, but simply does not get cold anymore. Since I bought the truck used, I don't know when the last A/C service was done, or even if it has ever been serviced.

    I know that I should have a diagnostic done on the system to see if there are any leaks, but after that - ? The original A/C system was an R12 refrigerant system. Does anyone here on the forum have experience with converting from R12 to R134a on these "older" trucks?

    Thanks in advance,

  2. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    I have converted several cars from R12 to 134A. The kits they sold were quite complete and easy to do and the instructions were also very clear but I also have 40 years experience in the refrigeration and A/C field. The only thing the kit did not have was a vacuum pump. It is important to know what the original charge was as the new refrigerant amount is 80% of that (if I recall correctly).
  3. csltrains96

    csltrains96 Rockstar 100 Posts

    dpeter - I was doing some review reading on a vacuum pump for evacuating the A/C system, and there was a gentleman that said when switching from R12 to R134a you should really replace the dryer and the hoses, as they could leak later on (possibly due to incompatibilities in oils?). Do I really need to tear the A/C system apart just to convert it to R134a and get the A/C blowing cold again?

  4. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    My experience has been very good with the switches that I have made. None of the kits required removal of the old oil or changes to hoses or O-rings to work. To be sure, there are incompatabilities with some oils and refrigerants and if you pick up some random oil charge off the local auto parts store shelf without KNOWING what you have in the system and KNOWING it is the same or compatable........ well I get off track here. No, you don't have to start changing parts unless of course they were broke to begin with. I have not kept track of all the ones that were changed but I do know of three that are still going with no problems after 9 or 10 years, two chevys and one Mitsubishi and they have all cooled as well or better than new. Get the kit and go for it. I have not seen one for a while, lots of do-it-yourself recharge but no conversion kits on the shelves but I'm sure the're out there.
  5. Chris Miller

    Chris Miller Rockstar 100 Posts

    You don't need to change out the hoses. Both systems use pretty much the same hoses and seals.
    Now, you do need to change out the accumulator and orifice tube, flush the lines, and vacuum the heck out of it. Mineral oil isn't compatible with R134. If a little bit is left after the vacuum and new parts, it won't hurt anything, but get out as much as you can. As for the R134 oil, 8 ounces of ester or PAG 150 will be fine. The system will probably take a little more than three cans of 134. Just check your pressure as you go. When you get the clutch cycling switch, the parts house should have a retrofit option for it. It'll have the old-style R12 plug but will work with 134.

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