Need AC Help

[pfijma]

Hello,

I am a new bee when it is about AC-systems.
I read the previous treads about converting a R12 AC-system to a R134A AC-system.
My AC-system needs service.
Can anyone tell me, when looking at the included picture, if the AC-system on my ’71 F250 has already been converted to R134A or not?
Thanks…

Paul

AC-System.JPG

[fordman]

the way to tell is the fittings to fill the system are larger with R134A than the fittings For R12. plus you are suppose to put a retrofit sticker on the truck when they change it over. but that isnt always done.

[pfijma]

Thanks…
A retrofit sticker is no where to be found under the hood.
What is the difference in size between the small (R12) and large (R134A) fittings?
Does anyone has some pictures of the large and small fittings so I can compare them?
In this way I can find out if my AC-system is already been changed over or not.
Thanks again!

[basketcase0302]

It appears from the above picture that you still have the old 1/4" gauge fittings on your compressor. The newer style 134A access fittings are a lot larger than the original R-12 fittings. Keep in mind that it could still have been converted to 134A refrigerant without the fittings being changed to the newer style.

I would be guessing to say that it still has R-12 refrigerant in it, and that you should be replacing the refrigerant with the newer 134A and proper synthetic oil.

Good luck!

[pfijma]

Thanks for the clear answer...
In additional to the oil do I have to replace the drier as well? Is it true that the comperssor pressure must be lowered because the pressure temperature relationship of R12 and R134a is different. And the sytem must be filled with 15-20% less R134a than the R12 specification.
I'm going to visit the local AC-service and see if he can help me out to change over to R134a.
I wonder what he has to say about this issue!

[basketcase0302]

pfijma on Thu Jul 15, 2010 2:01 am
Thanks for the clear answer...
In additional to the oil do I have to replace the drier as well? Is it true that the comperssor pressure must be lowered because the pressure temperature relationship of R12 and R134a is different. And the sytem must be filled with 15-20% less R134a than the R12 specification.
I'm going to visit the local AC-service and see if he can help me out to change over to R134a.
I wonder what he has to say about this issue!

Yes, a new drier is common once the refrigerant system has been opened to atmospheric pressure.
Yes, the 134A will be operating at different pressures, (sorry can't help you with actual gauge pressures it will wind up at/too many variables).
Yes, taking the truck to a local auto air shop would probably save you money in the long run.
You should also insist the refrigerant system be chemically flushed, (castrol makes a good flush kit).
And like Fordman said in addition to most junkyard compressors being junk, (especially if any part of the piping system has been opened to the atmosphere for any length of time).


edited for flush info

[pfijma]

Hi Jeff,
Many thanks for your support and good advise.
I will keep it in mind when taking the truck to the local air shop!