1994 R-134 specs?

[gsmaclean]

I had the steel line between the receiver/dryer and the condensor rust out and vent the refrigerant out of my truck's A/C. I spent some time reading the forums here. I replaced the line with a new one (hint: remove the passenger wheel well and come in from below), and replaced the orifice while I had it open. I charged the system with a cheapo R-134 can/hose thing from Wal-Mart without operating it, checked the pressure (around 30 psi), and then drove the truck for a couple weeks (without operating the A/C). After two weeks, the pressure is still the same, so I am going to assume that there are no leaks.

I got a venturi vacuum pump and a set of high/low gauges from Harbor Freight, and I plan to evacuate and refill the system. I know I'll have to charge it with (PAG?) oil first as well.

I see many mentions to "add refrigerant to spec", "add oil to spec", "add to pressures as per manufacturer" here, but I can't actually find anywhere what those specifications are. The crappy Haynes book I have for my truck basically says "for A/C work, send the truck to the dealer."

Does anyone have an idea what the proper pressures/oil amounts/etc. are for my 1994 Limited? Or where I might find that information?

My alternative is to evacuate, add a can of oil, add a can of R-134A to the high side (upside down), then start it up and slowly add a can to the low side, watching until the vent temperature bottoms out. Correct?

Oh, and I have my safety glasses (and gloves - frostbitten skin is no fun either) ready.

Thanks!

 

[zhanx]

not sure what the specs are but you dont need to add a can of oil unless its like 1-2ozs. cause you didnt change the compressor. (worked on many a vehicle and the manu, veries on the amount of oil between 1-4oz most of the time large being more oil) check the label of the 134 in a can it may contain oil already which should be enough. For pressure specs grab a thermometer and a pressure chart off line (google search term r134 pressure temp chart). r134 should be between 45-65 IIRC low side. But i've been mainly working on hummers so i am not going to stake anything on it.

 

[ma96782]

For your 1994:

Total Capacities Are,
Oil....7.00 oz
R134a........2.25 pounds

Aloha, Mark

PS....source: Haynes Automotive Heating & A/C (book #10425)

Pressure is for system at 80 degrees F ambient air temp at sea level
low side 22 to 50
high side 160 to 250

 

[Glacier991]

The AC on FORDs is different than on Hummers and in fact different than most brands of automotive AC in their workings. The principles of thermodynamics for AC are pretty simple... expanding fluid cools, compressed fluid is heated.

In most systems there is a valve that controls the expansion of the liquid into a gas (the "expansion valve systems" ot thermal expansion valve or TXV) There a set pressure should exist on the upsteaam and downstream side dependent on other temperatures.

In the case of FORD... there is a "valve" with a fixed hole in a disc (the orifice valve or more correctly Orifice tube) and the compressor will run until it reduces the low side pressure to a point that would freeze the system... then it shuts off and lets the pressure rise.... repeating this process over and over. The low side is controlled by a cutout switch that cuts out at around 25 PSI. This constant;y changing environment pressure wise makes it hard to adjust by pressures... vent temps are better. BUT! If you have an empty system, recharge it to spec and call it good. SO, you are in luck.

Let me recheck that 2.25 LB spec.... somehow I feel that sounds high. Just a a rule of thumb a system using R-134 will use about 70% of that same system using R-12. That tends to sound like an R-12 load... but let me recheck.

 

[shamaal]

There should be an EPA sticker next to the hood latch that gives the correct amount of refrigerant, spark plug type, gap, etc. Note whether it says R12 or R134a and ignore if R12.

You've read the forums, so you're aware that unless the system was evacuated moisture may be in the system leading to acids and premature failure.

 

[gsmaclean]

There should be an EPA sticker next to the hood latch that gives the correct amount of refrigerant, spark plug type, gap, etc. Note whether it says R12 or R134a and ignore if R12.

You've read the forums, so you're aware that unless the system was evacuated moisture may be in the system leading to acids and premature failure.

Thanks. I'll have a look for the label tonight. I just got the new receiver/dryer that I ordered from rockauto.com so I'll have a go at it this weekend. I plan to evacuate it fully before recharging it - I don't want to be doing this again in a few months!

 

[gsmaclean]

There should be an EPA sticker next to the hood latch that gives the correct amount of refrigerant, spark plug type, gap, etc. Note whether it says R12 or R134a and ignore if R12.

You've read the forums, so you're aware that unless the system was evacuated moisture may be in the system leading to acids and premature failure.

Had a look last night. Nope, no mention of refrigerant on any label. I found the label that specifies plug type & gap, but nowhere did I find any mention of type or amount of refrigerant.

 

[shamaal]

Odd, well at any rate.

Put 3 oz of oil in the accumulator and you should be set. Evacuate for no less than an hour. You will need a fairly hefty pressurized air source if you are using the venturi pump from Harbor Freight.

I read that the R12 stopped in 93, and R134a started in 94 so the 2.25 lb load should be for the R134a. But I agree it sounds high to me also. I also notice in the Haynes A/C book that apparently there were no Explorers built in 1995 and 1996. Hmmm....

In the absence of another source, I'd put 24 oz in and monitor the vent temps. If the temp begins to rise, you can always bleed it off.
I would call any temp in the 40's, while driving, a victory.

 

[Glacier991]

22 OZ is your system capacity in 134A. Good call Shamaal.

 

[gsmaclean]

Thanks for everyone's help. This weekend I finally installed the new receiver/dryer and orifice, lubed the new O-rings, sealed it all up and evacuated it. I put in a few ounces of PAG 100, and followed that with a 12 ounce can of R-134a (with UV dye, just in case), with the can inverted (sending liquid refrigerant in) into the high side port, engine off. With 12 ounces in it, I started the truck up, the compressor started to cycle, and I was showing a max of about 100 psi on the high side. Vents were still blowing warm.

I started a second 12 ounce can of R-134a, this time into the low side port (non-inverted) and as I did, the vent temperature started to plummet. Outside air temperature was 73 degrees, and by the time I got the second can into the system (put it in some warm water to get it all out), my vent temperature was 44 degrees, which felt damn cold to me. At that point the compressor was running continuously, with a sustained high side pressure of 250 psi. I unhooked everything and it seems to be running great!

Only snag I had was that it took me a few minutes to discover that the valves built into the quick-disconnect fittings that came with the manifold gauge set work backwards - counter-clockwise to close, clockwise to open.

 

[gsmaclean]

Incidentally, when I pulled the old orifice out, it was completely clogged with rust and crap from the line that rusted and failed. I'm glad I replaced it!

 

[shamaal]

Super!

Expect some spoilsport to come along and point out that if the orifice screen was clogged, it might have been a good idea to flush the system; but it won't be me.

Thanks for the followup, it should run for a while and you have something to keep in mind if you have to crack it again.

 

[gsmaclean]

Super!

Expect some spoilsport to come along and point out that if the orifice screen was clogged, it might have been a good idea to flush the system; but it won't be me.

Thanks for the followup, it should run for a while and you have something to keep in mind if you have to crack it again.

The line that rusted out was immediately upstream of the orifice screen (in fact, it was the line you disconnect in order to change the orifice screen) so unless something made it through that very fine screen, the system should be more or less OK.

But it works, so that's fine with me.