R-12 to R-134a conversion

[1993GMCSierra]

Hi all,


I want to fix the air conditioning system in my '93. It hasn't worked ever since I got it (compressor would cycle rapidly 3 years ago, nothing now), and I'd like a little comfort on those 90+ degree days.

The truck as it sits has R-12 in it, or at least, it had it in it. The shop I usually go to for stuff will convert it for about $90-100 total.


My questions to you are, if you had your truck converted, how did it cool afterwards? I'm looking up the A/C part numbers, and am noticing the condenser was upgraded in 1995 to a larger unit. Should I buy one to increase the cooling capacity of the A/C system?

The shop says all I really need to do is put on the new fittings, evacuate it, vacuum it down, and re-charge if it doesn't leak.

They have a $5,000 machine they use to do the whole process, but I'm not sure if it will get all the old oil out of the system or not.

I figure, I'd need to replace the accumulator/drier, orifice tube, and seals before I get it charged, is that correct?


I just want it to cool properly. I don't want to get it converted, only for it to not cool like it is supposed to.

 

[dcZ71]

R12 is a much more efficient refrigerant, fix what you have imo.

 

[1993GMCSierra]

I just went on ahead and loosened the nut that connects the hoses to the compressor slightly and heard a faint hissing, so it's still under a bit of vacuum anyway. I then jumpered the low pressure switch for about 30 seconds or so, no change in air temperature coming out of the vents, so I'm guessing it's pretty much out of freon.

My thing is, if I open the system to replace the O rings and such, I don't have a way to vacuum it down to get any new freon in there. IT has to be under vacuum in order to take freon right?

 

[Horns]

Unless you want to spend the money to buy the machine yourself then take it to a shop and have them discharge the system. You loosening the line, that hissing your heard is actually the freon leaking into the air, and letting freon just leak into the open air is HIGHLY illegal. Go to a shop that has the equipment to properly drain and properly dispose of the freon.

 

[1993GMCSierra]

Unless you want to spend the money to buy the machine yourself then take it to a shop and have them discharge the system. You loosening the line, that hissing your heard is actually the freon leaking into the air, and letting freon just leak into the open air is HIGHLY illegal. Go to a shop that has the equipment to properly drain and properly dispose of the freon.

Hi Horns,

I am aware that venting freon into the atmosphere is illegal, I was just checking to see if there was any pressure left in the system, or if it had all leaked out. Any venting is illegal, but I don't think a 1 second "fsst" is going to hurt anything, or at least not in comparison to letting it all out.

I just figure, that since it does indeed still have freon in the system, if I should just try to get a can or two of R-12, and add freon until the temperature at the vents is within acceptable range, then driving it that way for awhile.

I had my old Sierra converted, and it didn't cool worth a flip. I'd like to know if it was just a fluke, or if these trucks just don't convert all that well.


Anyone know what temps I should see at the vents with R-12, assuming 80* ambient temp?

 

[shelbyt.67]

I converted mine. The whole system was toast. The 134a works fine in 110* Texas heat. So yer little 90* won't hurt it at all. It sounds like u got a good system. I would change out the drier and o-rings and let the shop convert the fittings. The shop will vacuum it before filling, so don't worry bout releasing the vac. The one problem u may have is if that compressor is too old it will not be compatible with 134a. The shop will know fer sure one way or another.

 

[///RAGMC]

I converted mine after having to replace a bad hose. A friend of mine who is a AC tech told me to pull the compressor of the truck and drain the oil out over night then reinstall it add new oil and recharge the system Ive gone over 6 years now with no problems and freezes like no tomorrow

 

[1993GMCSierra]

I can't help but wonder why my old GMC did such a poor job cooling it all down then. I replaced the compressor, orifice tube, accumulator/ dryer, and all the O-rings before they converted it.

Result? 78* interior temps when it was ~90* outside. The engine struggled so much trying to run the compressor at idle and running warm down the road that I just stuck to the 2/55 method.

 

[1993GMCSierra]

double post...

 

[shelbyt.67]

Yeah I agree the r12 cools better. But thank a ****** liberal fer 134a. We gotta lotta real estate under the hood to keep cool. I put an electric fan in front of the condenser and it made a world of difference.