R134a A/C fresh charge
 

Hey guys,

I'm looking for some pressure info from you some of y'all who have done R134a conversions or have them on your truck with good results. Yes, I know R134a sucks in an R12 system but I'm not paying $51 for one can of R12 right now.

I went with the RED orifice tube this time because I have read that it is better with R134a.

I have 45PSI low side, 280PSI high side, used 3 cans, 12Oz each. It is a little over 80F out today and the lowest vent temp I have seen is about 64F with low fan speed. Not a very good delta. I have one more 12Oz can left and I was wondering if I should put it in. I have heard guys running 4 cans but these pressures are getting up there.

Thanks for any help. I don't want to sweat this summer like I did last.

http://www.eatoncomp.com/images/1991...m/IMG_1124.JPG

This is at idle. New compressor switch on the drier. Vent temps @ 68-70F ambient about 85F. Compressor remains engaged and does not cycle.

you have overcharged the system , it should be about 25-30 psi on the low side
and did you install 10 ounces of pag oil in the system , r134a will not work with the original mineral oil
the condensor on these trucks is large enough to work fine with r134a also

I completely rebuilt the system last year. It lost all charge due to a hose coming apart. I found it just flopping around in the engine compartment disconnected. Seems like it unscrewed even though I made sure all the connections were tight. I charged the compressor with PAG150 (I used the jar) and I also added a little more this time assuming some was lost due to the leak. The drier is a year old. I didn't get very good results after the rebuild, even with 25-30PSI.

As I was adding the refrigerant, I checked the temps as I went along. I didn't notice any temps under 60F. If 25-30PSI was optimal then I should have seen low temps at the vents, right? How many Oz of R134a should be installed in a completely drained system like mine?

I added the 4th can and I didn't notice any change in cooling. It gets down to 60F driving 55MPH but that's it. Compressor does not cycle.

I but the variable rate orifice tube in mine after being unhappy with the warmer evap temps. The tube is 30.00 or so, but I would do it again.

With the 4th can at idle.

http://www.eatoncomp.com/images/1991...m/IMG_1125.JPG

I was looking at those but they weren't in stock, plus they were 15x the price of a regular tube. If they are the difference between 60F and 40F at the vents, then I am all for it. What are you getting for vent temps? What were your pressures? How many cans did you use?

I put 80% 134 in a 12 system. This is normally very close. You also need to know how much oil is in it. I also check the top and bottom of the evaporator for temp difference. When you overcharge the evap temp rises. The picture of your guages look like you are on the high side and beginning to oversaturate the evap. Is your blend door closing all the way if you have one. My vent temps are 38 or so, depending on ambient temp and driving speed. It is comfortable and feels like A/C. I'm sure yours just does not feel like it is cooling. I hope this helps. I converted mine 5 years ago and added the variable orifice 3 years ago.

Now on mine I did the conversion and used the same tube, it was black IIRC. Anyway I started off at -28''hg of vaccum. And I put in 8oz of ester oil and charged to 38psi on the low side, I also brought er' up to about 1200rpm and added a bit more to bring it up to 38psi there. I get 43F vent temps with abiant temps of 103F, going down the road. Sitting in traffic it will raise to 50F.

Did you evacuate the system before charging? Without the evacuation any moisture in the line will turn into water droplets, however the dryer should eliminate most of that.

I always charged just until the compressor no longer cycles. The system will run better a little low rather then a little high.

I did vacuum the system down. Not sure what Hg because I don't have a gauge to go in between but I let the AZ rental pump sit on there for a good 30 minutes while I tightened down the compressor belt and a few other things.

I guess I need to let some out. Does anyone remember how many cans of R134a they used?

I am pretty sure the blend door is closing but I can shut off the heater core to test it. I'll do that and see if there is any difference.

you want 25-30 psi on the low side 35-40 is overcharged and causes higher evap temperature , not to mention the additional stress on the compressor
you must have a stuck blend door causing the 60 degree air

I shut off the heater core and at idle, I get 60F out of the center vent on high A/C and high fan. It was 81F out when I ran this test.

Before I let out any valuable R134a, I would like to know what the total recommended charge is for the system. I'm finding very mixed results online and I don't even see mention of an R12 charge amount in the truck's manual.

So, if it takes 48Oz of R-12, AKA 3 cans, how many does it take for R134a? As far as I know, R134a runs higher head pressures and less efficient; especially in R-12 systems. Any thoughts?

I also removed the entire A/C system last year and cleaned the evap and condenser. I also flushed everything with A/C flush. It was VERY dirty.