Retro fitting for 134a

I am planning to retro fit my 1989 S10 truck.
Truck info: 2.5 Liter Eng., Man. 5 speed, single cab, 2 door.
The truck has been sitting up for two years due to my being out of town working. I have changed all fluids and put it back on the road, everything checked out fine, runs good and all except the A/C has leaked down, so I figured this would be the perfect time to retro fit. I need advice on which parts I need to replace, and since I have an expantion valve do I have an orfice tube? Also the dryer/accumulator with sight glass is mounted in the grill with condencer, will these parts be replaced with stock factory items or will they be replaced with aftermarket items, either way, can they be purchased at a regular Parts supply house? I also need to know step by step proceedure for retro fitting, parts changing getting it going again. Thanks for any Info and/or advice.

Change the reciever dryer to a R-134 a dryer.
On a change over it needs the correct ac oil added and right amount of R-134a
Old R-12 left in it needs reclaimed.
Systems need pumped down with a vacuum pump and hold the R-134a charge down 10-15 % to help on high side pressure.
MT

MT, thanks for the reply, but I still need a little more direction. Am I correct in thinking that I need to use Ester oil, and also do I remove the old oil in system by flushing. If so what type flush do I use, also I have been told not to try to flush the compressor, how do I remove any oil that might be in the compressor, remove it and just pour it out?
Thanks, Charles

One more question, on my 1989 S10, it has an expansion valve, do I have an orfice tube and where would it be located?
Thanks again, Charles.

One more question, on my 1989 S10, it has an expansion valve, do I have an orfice tube and where would it be located?
Thanks again, Charles.

If it has a expansion valve there is no orfice tube.
You can not have both.
MY

MT, thanks for the reply, but I still need a little more direction. Am I correct in thinking that I need to use Ester oil, and also do I remove the old oil in system by flushing. If so what type flush do I use, also I have been told not to try to flush the compressor, how do I remove any oil that might be in the compressor, remove it and just pour it out?
Thanks, Charles
Yes ester oil.
On the compressor you will have to remove it and turn upside down and drain it.
Or just put on a new R-134a compressor

A new receiver dryer will take care of dryer oil .
Take lines off of both ends and.
The evaporator and condenser can be flushed with a flush kit.
ACkits.com has a lot of good info on it.
http://www.autoacforum.com/

http://www.autoacforum.com/messageview.cfm?catid=20&threadid=7927

MT