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Retrofitting A/C system

Discussion in 'Chevy Trucks' started by JB, Apr 9, 2000.

  1. JB

    JB Member
    Messages: 46

    I am planning to retrofit my a/c system from R-12 to R-134A. I have the kit to do it but have been told that I should flush the system first. The kit says that I do not have to flush anything, just add the Poly oil and R-134A. The system has been nonoperational for the last two years but has not been exposed to the outside air. I will vaccum the system out first then charge with R-134A. Any ideas? (this is in an 88 K-5 Blazer)
     
  2. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    We use only ester oil in our retrofits,and we dont flush unless it blew a compressor or something.you should consider installing a new orifice tube while you are at it,the screen may be plugging up with metal from a compressor on its way out,and you will need the system working at 100%,because you are going to lose about 10% capacity from the conversion,if it was cooling borderline before you wont be happy now.<p>----------<br>John D<br>
     
  3. JB

    JB Member
    Messages: 46

    John; Should I replace the accumulator? If i have to replace the oriface then I will have to open the system up and expose it to moisture. I suppose I will have to install a high pressure cutoff switch also because of the higher pressure of the R-134A? What about the compatability of the oil in the compressor? Thanks in advance. JB
     
  4. robkel

    robkel Junior Member
    Messages: 9

    jb, A flush of the system should not be neccesary unless you had contamination due to hose deteriation or metal contamination from bad compresser.We have not seen any performance loss on any of the hundreds of conversions we have done . I think that is <br>just simply untrue. The r-134 is actually more stable and helps with compresser longetivity [we have some vehicles with over 150,000 miles that are still going strong on original compresser and 134 from factory].. hope this helps . By the way .. a factory fan clutch is crucial to low rpm ac performance [or better yet ,, twin electrics] just be aware of cheeso fan clutches, they greatly effect pressures and performance of ac ... see ya
     
  5. robkel

    robkel Junior Member
    Messages: 9

    jb , No fancy high pressure switches are neccecary , accumulater not necc either , system will operate at same pressures as before. Replacing orfice and a good vacume is a good idea though,
     
  6. robkel

    robkel Junior Member
    Messages: 9

    ester oil is compatible with oil in r12 // just dont over do it [too much is bad] just follow retrofit instructions
     
  7. razz

    razz Junior Member
    Messages: 9

    A/C retrofit

    It's all good,however...if you are going to do it right,I would follow Section 609 of the clean air act ammendment of 1990. It is the way the Feds say you have to do it.
     
  8. wyldman

    wyldman Member
    Messages: 3,265

    Replace the dryer.It will help.The dessicant in the old dryer will be toast after all these years.

    New orifice will help as well.Use a blue Ford orifice tube for better performance.

    You may need to run an electric condensor fan,as the factory clutch fan may not pull enough air across the condensor to cool well at idle.Sealing the condensor to the rad will help too.

    The high side pressures are higher with 134A,and you need airflow across the condensor to keep it in check.

    Most of the retrofit kits have special oils,which are compatible to blend in with the oil already in the system.I have used both PAG and ester oils with no problems
     
  9. 75gmck25

    75gmck25 Senior Member
    Messages: 119

    I started an earlier thread about problems with the A/C on my '75 GMC, but my solution only lasted about 3 days before the A/C is out again - with the same symptoms.

    A short recap on my problem - I converted to R134a a year ago after a compressor failure, but during the last month or so the system was not cooling and appeared to be plugged. When I had it evacuated and opened it up I found the orifice plugged with black grit, but rest of the system appeared to be clean. I figured it might be leftover debris that was missed when I flushed it before the conversion.

    However, if last night's failure means I now have more grit in the system (haven't opened it up to verify yet), then it looks like the rebuilt A6 compressor may be self-destructing internally.

    If I use my warranty to get another identical rebuilt Murray compressor, can I expect it to also only last a year? I could try to find a better rebuilt or get a new APCO compressor for $250. However, if I do that its all additional out of pocket.

    I'd like to get this system up again and have it last for a few years without major work.

    Thanks

    Bruce
     
  10. wyldman

    wyldman Member
    Messages: 3,265

    It sounds like the contaminants in your system have taken out the new compressor.

    Whenever a compressor is replace,especially for an internal failure,flushing and replacement of components is necessary.A lot of times you won't get all the crap out of the condensor just by flushing,so it must be replaced.The condensor is where the majority of it goes after a compressor failure.Dryer replacement is also recommended.

    If you put on a new compressor,get everything completely flushed,and look at replacing the condensor.
     
  11. 75gmck25

    75gmck25 Senior Member
    Messages: 119

    When I retrofitted it last year I replaced the compressor, filter/dryer and orifice, and flushed the rest of the system. We used A/C flush and compressed air on the condenser and evaporator, but it may not have gotten everything in the condenser. It worked for about 11 months before it gave up the ghost.

    If I need to replace the condenser, I want to look at the new parallel flow condensers. Does anyone have any experience with fitting them to the older (73-87) GM trucks?

    The parallel flow condensers are not much more expensive, but are not designed as direct replacements. I would need to fabricate mounting brackets, and get an A/C shop to fabricate adapters so they will mate with the standard GM hose fittings.

    Bruce
     
  12. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    wow,this is an old post!
     
  13. wyldman

    wyldman Member
    Messages: 3,265

    It should be to hard to adapt a universal condensor to the front of the truck.Any good A\C shop should be able to sweat the neccesary adapters.They should also be able to help size the new one,as the R134A needs a little more condensor to cool properly.
     
  14. razz

    razz Junior Member
    Messages: 9

    A/C retrofit

    Hey Bruce, just thought I would share with you my experience. I own an 87 K20. During 5 years of daily drivin and reconstruction of my truck, the A/C was disabled. As my project neared completion, over 18 months ago, I restored the A/C to full working order. It has performed flawlessly since. This did not come cheaply {$750} in parts, however I saved much $$$ doing the work myself. I replaced everything...hoses,rebuilt compressor condenser,evaporator,orifice.o-rings,reciever/dryer,and heater core. I flushed all of the new parts,except the compressor, with denatured alcohol,followed by compressed nitrogen. The system was then assembled using the proper amount of oil for each component. Oil is sometimes added to compressors and sometimes it isn't,check the source. The evaporator reqires 1-2 ounces of r-134 oil. The condensor needs about 2-4 oz. The dryer needs about 1-2 oz. Use the Ford orifice[blue].Lube all the o-rings. Make sure all connections are tight and pull a good 20-30 minute vacuum. Make sure the system holds a vacuum and recharge to specs. Yeah, it doesn't kool as much as R-12,but its what it is... Good luck ......
     
  15. 75gmck25

    75gmck25 Senior Member
    Messages: 119

    Razz,

    Thanks for the info. I followed the same basic procedure last year, but did not replace the condenser, evaporator or liquid line. However, I flushed them with A/C flush and blew everything dry with compressed air.

    My problem is I'm not sure what caused the black grit that I found last week when I took the system apart to find out where it was plugged. The grit might have been left over in the condenser and was missed by the flush, but it was there for 11 months before it plugged the orifice. I think a more likely possibility is that the rebuilt compressor has started to come apart internally.

    If I end up replacing the condenser this time, I'm going to look at the parallel flow units. One of the parallel models is almost the same size as the original condenser in the truck. I just want to do some more research on how hard it will be to get the fittings to adapt. The parallel unit uses a 5/16" #6 fitting and a 13/32" #8 fitting. My liquid line is 5/16", but I don't know if it would mate with a #6 fitting. The other hose on the truck looks more like 1/2" than 13/32.

    Bruce
     
  16. wyldman

    wyldman Member
    Messages: 3,265

    A good A\C shop will be able to make up hose\pipes\adapters to make the parallel flow condensors work even if the line sizes are slightly different.