I've heard that many of the 1989 through 1993 vehicles can be easily converted from R-12 to R-134a refrigerant simply by recovering the R-19 that is left in the system (not sure how much is in mine because it's not enough to run the system right now and needs a recharge)
and then add the refrigerant oil for the 134a and the r134a

Will this work on my 1990 F350 with the 19D629-BC compressor?

 

It might cool, but it won't last very long. For starters, mineral oil is not compatible with R134a so at the very least you must drain all the old oil out and flush the system before putting in R134a.

 

If you are planning on keeping the truck, change the hoses to ones that are compatible. Flush the remaining parts well and blow out with air. You will need a new orifice tube sized for r134.

 

Looks like the previous owner actually already converted it over to 134a with the proper fittings. Only problem was the schrader valve got bent and leaked out the refrigerant.

 

The truck has the R-134a fittings that someone previously installed but they installed them without removing the ford factory schrader valves so when they tightened down the adapters on top of those old schrader valves (I'm assuming that the Ford factory schrader valves were supposed to be removed before screwing on the adapters that have their own schraders?), it bent the pins which I'm sure why it all leaked out. I don't know for sure if they changed out the oil so I'm going to dump out the old oil from the compressor but I do not know how much oil to add to the compressor and I can't see a sticker in the engine compartment or on the compressor to tell me how much oil to add? Is there a way to tell if the compressor is still good because currently it's not working but the system is empty.

 

pull the orifice tube out. there is a screen filter on it. if it's clean you are good to go, if it is full of black stuff like mine was you should replace the compressor. Easy to pull from an empty system, it is in the skinny line right next to the dryer.

iirc, there is also something different about the media in the dryer between the 2. i used a new one for a '96 when i converted. The pressure switch on the dryer is different psi between 12 and 134, and the threads changed.

also 134 compressors have an addiotal port on the high side for use with an over pressure switch that was never needed on the r12 systems.

 

Where is the orifice tube located and how do you flush the system?

 

Not sure on what is the proper flush, but compressed air is a must. I ended up replacing everything except the evaporator.

 

the orifice tube is inside of the lines. watch a youtube video. easiest way to explain. get all the old oil out and also remember that the inside of the condenser has so many small passage ways, it might be a good idea to just replace, since there is no real good way to dislodge the obstruction from any external operation. the more restriction, less efficient. flushing? I have never done this but there is a product in a can that is offered. Everyone seems to make it. Castrol, wurth, robinaire, and others. typically uses compressed air, a solvent solution, and circulates through the system, dislodging and removing any light weight and bigger debris.


Try to remove as much oil as possible, and keep in mind that the oil is very important, I am not positive on your system, but if flushed and new parts installed It seems to be ~ 8 oz oil I will search and return if that is wrong. Pag 46 I believe.

 

some light reading for ya.
my compressor was toast, and the reman unit i got was filled with oil as delivered. mine suffered "black death", hopefully yours is in better shape. use PAG46 for r134a
Ford Light Truck Refrigerant and oil capacity charts || TechChoice Parts

and here's a thread i used to help me out. R12 to R134a -- How to do it?? - F150online Forums