To save money, I tore down my old dealer-install A/C unit, and rebuilt it using all of the same old parts. I am having a couple problems though. The new system is 134a, so I need to remove the expansion valve and put the new one on. It seems to be a smaller thread dia. than the old one. Any ideas?

Also, since the new is 134a, and the old was 12, it says to remove all the old stuff from the lines. Well the lines have not been attached in years. Will there be any stuff left in them? Should I run a blast of air through there for safe measure? Any other tips? Thanks,

 

I have done many r-12 retrofits, all have gone well. Honestly I have never changed expansion valves even though I know that to do sois supposed toraise the efficiency of the r-134, but all of my conversions have cooled well anyway.

Concerning the removal of the old stuff remaining in the lines, don't worry about it, that stuff should be long gone with the possibility of some oil being left in the lines / condenser / evaporator being quite low, and trust me, a little bit of the old oil wont hurt anyway.

You will want to use a new drier for sure, and if the lines have been disconnected for a long period you may have some debris in the ends of the lines and so forth. Clean out what is visible, and don't worry about what you can't see because the refrigerant oil will not let loose of any trash in the lines anyway,,, so don't worry about it... never had a problem.

You will also need a new compressor if the compressor on your car is not "Ester Compatible". If it is compatible it will be labeled as such.

If you are going to fill the system yourself, (no vacuum pump), purge the system of air by "burning" a can of refrigerant in the system prior to adding the refrigerant oil. (release a can of refrigerant into the system while leaving the system open in a place that will allow full circulation)

 

I plan on "building" the system (hoses, dryer, evaporator, etc.) and then taking it to a shop who said they'd charge $80 +refrig. to change it over.

The compressor is an R-12 Sanden Compressor.

If I can't end up getting the exp. valve off, or it's not the right size, I may take your suggestion and just leave it on there.

 

R134 also runs at higher pressures than R12 so it is also recommended that any rubber hoses get upgraded to the thicker 134 hose. I had ARA do it here for me locally in So Cal for my 92 explorer (but I kept the R12 system anyway). JMD's correct about the compressor having different ester resistant components in it as well. Why don't you think about keeping it R12 (its a better gas to start with) as it going to cost a lot more in new parts than the price of a R12 top off.

 

lol, well you can't legally buy R12 anymore. I still have access to it, but I just figured since this thing has been sitting for a while, I need to clean/fix it up. Since I'm fixing it up, I might as well upgrade to 134a. But, I didn't think about the hoses.

 

While I will agree that R-12 is a superior refrigerant, IMOit is just too expensive these days. I think it is still available to licensed and certified technicians.

I don't like the idea of getting a second mortgage in the event of accidental loss ofmy refrigerant!

 

Just go with the 134, it's getting hard to find R12 now, so it will be worse in the future. With 134 you can have it serviced anywhere.