A/C question

[vinnieTy]

It has been years since i have worked on an a/c system that contained R12 freon so im asking for some assistance on refreshing my memory. My truck still contains the R12 freon and works ok. I think it can be bit colder but before i do any changes I want to make sure im not low on Freon. I have r12 cans so my question is do i need the dual gauges to read the low and high side to see if i'm low or can i just get a gauge like they sell with the 134 cans and go from there. I have read on line that i cant use the gauge from a 134 bottle as the freon is more dense so the reading will not be correct, is that right. As always thanks in advance for the help.

 

[atkonkler]

Re: A/C question

Pm Davep. He knows everything....

 

[NM_TY_Guy]

Re: A/C question

R-134a gauges will not work for r-12 you will need the correct gauges to read the pressure and a temperature pressure chart to figure fill volume.

 

[Don W.]

Re: A/C question

I had an interesting experience with this. I volunteer at the local JC diesel class. Next door is auto. Got to talking to the the guy who teaches AC and for a teaching "moment" he used a fancy-dancy machine to convert the truck. I thought it was SnapOn but haven't found it in a short search.

Very interesting. It sucks out whatever R12 you have, vacuum tests the system and refills it with R134. Hoping I have my numbers correct... Anyway Went to Kragen and bought BOTH GM conversion kits. (It took one from each to convert the fill valves as I recall.) We had to fill it twice, I forget why. On the second fill it's cooling fantastic but the compressor is cycling. Teacher says it a pressure issue. Well it turns out that our pressure switch is adjustable. (At least mine is) Pull the connector and there is a screw down inside. I seem to recall I backed it off 2 turns. (Could be wrong here.) After that worked like a champ.

I must have a small leak somewhere because it eventually bled down. I was unable to go back, school ended.

Anyhow, FYI, our system is an A/C Accumulator system as opposed to a Receiver-Dryer system.

"An A/C accumulator is used in cars that have an orifice tube and not a thermal expansion valve. An orifice tube is found in automobiles created by Ford or GM."

For some reason it seems to me with our system the accumulator doesn't need to be changed but if we had a receiver-dryer system the dryer would have to be changed. Someone should check that.

This is just about the end of my A/C knowledge/experience..:rotf: It was fun to watch the kids learn, I learned almost all the above, and I did have A/C for a few weeks.

HTH

 

[1blkc4]

Re: A/C question

R12 is a lower pressure than 134a I would be leery about converting . I still have R12 in my system too . Someone should chime in .

 

[Poconojoe]

Re: A/C question

R-134a gauges will not work for r-12 you will need the correct gauges to read the pressure and a temperature pressure chart to figure fill volume.

Pressure is pressure, it doesn't mater what refrigerant you're measuring. The issue with using 134a gauges, most of them have the wrong fitting for anything other then 134a. I have a very niece set of Fieldpiece digital gauges, which if you tell it what refrigerant you're using, it does all the calculations for you. This comes in handy if you're trying to set a TX valve for the proper superheat, inside a walk in freezer at 10 below zero. Anytime I have a R12 system and the person doesn't want to pay the price for R12, I have them get Freeze12, its a drop in replacement. Yes, you can charge the system by only having access to the low side, a lot of refrigerator systems only have low side ports.

 

[Poconojoe]

Re: A/C question

R12 is a lower pressure than 134a I would be leery about converting . I still have R12 in my system too . Someone should chime in .

134a isn't considered a high pressure refrigerant like some of the newer ones like the 400 series. When the vehicle manufactures switched to 134a, they didn't make any major changes to their hoses and seals other then the seal material to be better suited with the oil.

 

[0966Sy]

A/C question

R12 service port fittings are different than R134, so yes you will need R12 fittings on your manifold set to do a correct service check. You will need to see both high and low to check system performance. Remember that A/C systems use oil to lubricate the compressor. Depending on how much your compressor has been used it may be wise to evacuate the system and replace the oil with new. But at this point you would be better off upgrading to 134. R12 uses mineral oil as 134 using PAG. Oils should NOT be fixed, requiring a system flush to upgrade to 134.

Get a set of decent gauges for R12 from an autoparts store like Napa. Get a R12 chart and a temp gauge for inside the cab and outside the cab and charge on the low side as needed. Depending on your results you might need to adjust the low side switch or replace the oriface tube.

 

[Damian]

Re: A/C question

R12 service port fittings are different than R134, so yes you will need R12 fittings on your manifold set to do a correct service check. You will need to see both high and low to check system performance. Remember that A/C systems use oil to lubricate the compressor. Depending on how much your compressor has been used it may be wise to evacuate the system and replace the oil with new. But at this point you would be better off upgrading to 134. R12 uses ester oil as 134 using PAG. Oils should NOT be fixed, requiring a system flush to upgrade to 134.

Get a set of decent gauges for R12 from an autoparts store like Napa. Get a R12 chart and a temp gauge for inside the cab and outside the cab and charge on the low side as needed. Depending on your results you might need to adjust the low side switch or replace the oriface tube.

These are the fittings Im using and they fit perfect: http://www.oreillyauto.com/site/c/d....oap?ck=Search_N0701_-1_-1&pt=N0701&ppt=C0052

 

[0966Sy]

A/C question

CORRECT!!!!! mixed them up. Mineral oil for R12, I always use PAG on my retrofits and couldn't remember the other I never use because I don't work on R12. Many of the older fellers will know the R12 systems as stated above by Dave.

Mineral Oil can also be used to treat Arthritis too, going to start using that to remember it's for R12.

 

[vinnieTy]

Re: A/C question

Thanks everyone for all the knowledge and great information. As of right now i changed the a/c clutch and it worked out good for the 15 minutes of test driving i did. The old clutch just would smoke because of it slipping. For now the a/c is cold enough for me and a passenger but not for my kids in the back seat but we all know these trucks are not meant to be that cold as of the amount of heat the motors produce.

Well here are a few pictures of the new clutch installed and another of my son who made me laugh very much when i came back to the garage and seeing him sitting in the truck. HAHAHA He said its too cold HAHAHAHA.

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