Converting to 134a is about $10.00 worth of parts. (not including oil and coolant of course)
The things that need to be changed are the "orifice" (expansion tube), the type of oil used and the rubber o-rings.
r134a requires ester oil "PVE"
Replace all the "red" o-rings with the "green" ones (real easy on this truck) it's all one hose.
The expansion tubes are $3.00 at any parts store and are not vehicle specific.
The expansion tube is in the high side pipe going into the bottom of the evap. a little tight in there, but the fitting is accessible from the top once you get the receiver out.
There is enough room to pull out the old expansion tube and slip in the new without having to pull the condenser.
With some practice I can do this conversion in 30 min. First try took 1 hour.
If you are unequipped to recharge, just by the cans of 134a with oil already in it. Get the can with the gauge, real simple - add until the needle is in the blue zone.
You will need to borrow or rent a vacuum pump to get the moisture and oil out after having the system open, or just take it to a shop for the vac and recharge.
Cheap DIY conversion.
Very pricey if done buy a shop. Most shops charge $600 plus a bunch of bogus environmental fees because of the r22 (that has already leaked out!)
It does NOT need to be flushed or cleaned in any manner to get the old oil out, the vacuum will do that. Not critical to get it all.
134a and r22 have very similar compression-to-liquid properties, so it is NOT necessary to replace the compressor or make any other modifications. The expansion tube orifice size is what determines the end running pressure. Also NOT necessary to change the high and low pressure switches.
You can even get the "conversion" sticker on e-bay,,, just to make it all California compliant.
To make shopping easier just tell the parts guy you are working on a 94' , ask for a expansion tube and a box of assorted o-rings. In Cali if you tell them you are doing your own conversion they might not sell you the parts!
