I recently the AC in my '91 F-250 converted to R134. The shop removed all the R12 and recharged with R134 without running a cleaner through the system. I got about 1.200 miles from home when the compessor froze up. The shop that replaced it said that there should have been a cleaner ran through the system before recharging with the new refrigerant because the oil in the two refrigerants are not compatible causing the compressor to fail. The first shop denied this. I would like to know if I was misinformed, thanks.

 

If the first shop charged the system with R134a and PAG oil they set you up for failure. It's well known and documented the older style mineral oil used in automotive R12 (not R22) systems is not compatible with PAG oil. At the very least they should have flushed the system with a cleaner....a few times IMHO.

Ester oil is compatible with either one but personally I do not like converting a R12 system over to R134a. Too many pitfalls that can bite you.

The other part of this story is asking if the system was working before you had the shop convert to R134a? Was the system ever open to the atmosphere for any length of time? There could be other factors leading up to this failure, but should have been addressed by the original shop the first time around.

 

Quick look reveals an orifice tube and receiver dryer which also should have been changed after flushing system thoroughly.
Regards,Ed

 

I had changed the reciever drier prior to having the refrigerant changed.

 

You lost me here. You changed out the receiver/drier then changed refrigerant? Was the system charged with R12 after the new receiver/drier was installed? Then you had the system converted?

There is a phrase for this : "A series of unfortunate events"

 

I was told by the shop to change the reciever drier so I did, then they removed the R12, it held vacuumn ok so they charged it with R134.

 

There is no way you could have changed the receiver/drier without releasing the R12 to the atmosphere or evacuating the system.

I am not trying to be a butthead, just pointing out there has to be more to the story here. This all adds up to one thing, half-a**ed A/C conversions are full of pitfalls. You were misled by the first shop. To their defense you should have read up more on what is suggested in order to have a successful conversion. An informed consumer is the best defense.

Take my comments and opinions for what they are worth, the cost was free.

 

When I changed the reciever drier there was no pressure so someone else may have had the system open at one time, also I didn't find an O-ring on one of the fittings. I just told you the sequence of events, when I took it in after changing the reciever drier they drew out anything that was left before charging the system with R134. They did not run any cleaner through it.

 

A real conversion should include the replacement of EVERY o-ring in the system with HNBR o-rings (the green ones). If they didn't flush the system they screwed you up.

This should be very informative:
http://www.sanden.com/originals/images/retro.pdf

 

I know it's definitely not the right way to do it, but I've used those conversion kits from Walmart on several vehicles. Just screw on the adapters and fill it up. Always worked great and never had a problem with any of them.