I just finished replacing the compressor o-rings with HNBR and doing an evac and recharge on my '93 Sport. It was my first time using a manifold gauge set and dong more than a top off, so I am a little green. I couldn't find any system capacity spec for the 1st gens, just one for a '94 which was 22oz of 134a.

1.) Does my '93 have the same capacity as a '94?

I got between 1 1/3 to 1 3/4 cans(so 16-21) of 134a in the system with pressures swinging around ~30-50 low and ~140-180 high with the compressor cycling about every minute while idling in the driveway. Vent temps stayed right around 39-41°F with ambient around ~67-70.

2.) The low side pressure and vent temps seem on-target, but the high side pressure seems about 50psi low from the reports I have seen. Do I need to add more refrigerant?

Did you put any oil in the system?

I am getting ready to do the same thing, so anybody with experience, please chime in.

Nope, no extra oil. Many years ago it got a cheap 134a conversion kit(gasp!) when I didn't know jack about A/C systems. It got the included charge of ester in addition to the original stuff. If anything, it probably has too much. At least the oil was still clean and clear when I had the compressor off today. I know it should be flushed and completely gone through with a new drier and oil, etc, but I need to run it the way it is for right now.

you need to run it with oil, period, or your compressor will die

I said there is oil in it.

I just finished replacing the compressor o-rings with HNBR and doing an evac and recharge on my '93 Sport. It was my first time using a manifold gauge set and dong more than a top off, so I am a little green. I couldn't find any system capacity spec for the 1st gens, just one for a '94 which was 22oz of 134a.

1.) Does my '93 have the same capacity as a '94?
<snip>

2.) The low side pressure and vent temps seem on-target, but the high side pressure seems about 50psi low from the reports I have seen. Do I need to add more refrigerant?

#1, AFAIK, yes.. BUT I just put in full 2 cans in our '92..

#2 What was the ambient temp? Our '92 is normally in the 200's (mid) at 100F+ ambient temp using a variable orifice tube (brings up the pressure at idle).

My "guess" is we normally over charge the system which keeps it from cycling very often. Actually, last time I checked it it didn't cycle at all at idle and at higher rpms it "might" once in a while, but normally it didn't (low pressure drops at higher rpm).

~Mark

Thanks. :)

It was in the high 60s outside. I don't want to add more 134 if it might send the pressure too high when the ambient temps rise(100-110 range in summer and the Explorer is black).

Get yourself the right tools for the job.. You'll need a R134 manifold gauage set, a air vacuum pump to remove moisture & stuff from the ac system. You can get both tools for about $45 & 15 at the local harbor freight if your on a budget. When your charging the system your high pressure should be 2x + 50 the ambient temperature and low should be in the 30-40. Closer to 35 is ideal.. Get a few cans of R134 and the proper tap. Also wouldn't hurt to get a leak detector sniffer.

Get yourself the right tools for the job.. You'll need a R134 manifold gauage set, a air vacuum pump to remove moisture & stuff from the ac system.

That's probably how I evacuated the system, filled it, and knew the high and low side pressures....;)

I just finished replacing the compressor o-rings with HNBR and doing an evac and recharge on my '93 Sport.

When your charging the system your high pressure should be 2x + 50 the ambient temperature and low should be in the 30-40. Closer to 35 is ideal.

Thanks. The high side pressure wasn't much lower than my result using that equation, so I must not be far off the mark.

make sure that the old system oil for R-12 is flushed out of the system. There is a synthetic oil that is compatible with both,I use Napa's brand, and won't plug up the oriface tube.There is a tracer dye in it which will help you find any leaks later. Most of the oil will be in the accumulater, condenser, and evaporater.