R12 Conversion to R134A?

[1977_LEROY]

I know my compressor is good and original but not sure if system was converted to R134A... the high and low pressure fittings look newer than original vehicle. I just put a belt on the AC compressor and it runs. I know the system has some pressure on it but it does not get cool when I turn on AC. Should I look for someone to just add some R12 to the system and see if the AC will work or do I need to just convert the system over to R134A? If so, what is the best way, economical way to do this? Or is it best to just put R12 in and do it next winter once it cools off. Any advice is greatly appreciated.

[gchemist]

Is the condenser stock? R12 and R134 use differenty styles of condensors. If you run R134 through a R12 condenser, it will not cool down enough. Each uses a different amount. Each has different operating pressure too. Specific R134 condensor and new hoses are needed for R134.

[bnoon]

Originally Posted by gchemist

Is the condenser stock? R12 and R134 use differenty styles of condensors. If you run R134 through a R12 condenser, it will not cool down enough. Each uses a different amount. Each has different operating pressure too. Specific R134 condensor and new hoses are needed for R134.

I have not replaced the condenser on either of the vehicles I swapped to 134 and both had ice cold ac in 100 degree heat. Only parts I swapped were the connectors, oil, and refrigerant.

[Skunksmash]

My truck came retrofitted but hey its good to know the government wants to switch to that stuff that is $150 per can, isn't it?


They haven't got it done yet some I'm hoping they won't be able to.

[SCOTI]

Originally Posted by gchemist

Is the condenser stock? R12 and R134 use differenty styles of condensors. If you run R134 through a R12 condenser, it will not cool down enough. Each uses a different amount. Each has different operating pressure too. Specific R134 condensor and new hoses are needed for R134.

When I went to purchase a 134a compatable condensor for my CC dually, I was looking for the largest unit I could find because research indicated the larger the area the better it would cool. I contacted an aftermarket source that builds them to spec & he told me there was no need to switch to a different condensor given the dimensions of my original unit. This surprised me so I asked about the info I had learned while searching the net (134a req'd diff surface area; 134a/serpentine condensers were more efficient; diff types of condensers).

He informed me that the difference would be minimal @ best (indicated I might see a 1-2° difference @ the vent max). He said I would see better gains ensuring the pressure & freon/oil amounts were optimal for 134a & that was the most common mistake when people complain an original condenser wasn't effective after a 134a conversion.

After telling me that, he said he would be glad to sell me one but wanted to be honest about any improvements (this being a BBC/TX heat application).

My 90 was converted to 134a w/original parts & chills you out. My buddies Jeep Gran Cherokie was converted using original stuff & can freeze you out @ lower speeds. I stuck w/the OE sized unit for my BBC/CrewCab application based on how well those others worked.

If I'm not happy w/it, I'll have a true Parallel flow custom unit built w/the largest dimensions possible (Parallel flow = better than 'tube & fin' R12 unit or standard 134a compatible Serp units).

[Keith Seymore]

Originally Posted by SCOTI

When I went to purchase a 134a compatable condensor for my CC dually, I was looking for the largest unit I could find because research indicated the larger the area the better it would cool. I contacted an aftermarket source that builds them to spec & he told me there was no need to switch to a different condensor given the dimensions of my original unit. This surprised me so I asked about the info I had learned while searching the net (134a req'd diff surface area; 134a/serpentine condensers were more efficient; diff types of condensers).

He informed me that the difference would be minimal @ best (indicated I might see a 1-2° difference @ the vent max). He said I would see better gains ensuring the pressure & freon/oil amounts were optimal for 134a & that was the most common mistake when people complain an original condenser wasn't effective after a 134a conversion.

I think we used to put a lot of extra cooling capacity (both engine cooling and AC) in these trucks, because we test at Death Valley and/or Davis Dam at super high ambients and GVW/GCVR loading.

So - those of us who use them just to haul our own selves around, at curb weight, are not taxing the cooling systems that much.

I remember the time I heard a Powertrain cooling engineer say "...we could take some radiator out and save money" I didn't know what he was talking about.



K

[1977_LEROY]

Everything to my knowledge is stock except the 1995 Tahoe 350 V8 that was installed before I bought it. The original engine blew up.

[cool68]

so, how do you flush out R12 since shops do not accept that discharge. then just fill system with 134a? so many different answers to a common need, especially with high temps already here in Calif

[kalbert]

The cheap way:
Have any remaining r12 recovered professionally (unless you are equipped do do so). Screw on adapter fittings. Draw vacuum on for 30 minutes. Charge with 134a and an oil charge. Don't expect it to cool very well, don't spread half truths around the Internet about how 134a doesn't work. This was the cheap way, remember?

The "right" way:
Have r12 recovered professionally. Flush the condenser and evaporator to remove any debris and old oil, make sure you get all the flushing solution out. Don't flush the rubber hoses, the tiny amount of mineral oil left in them acts as a barrier. If you want to get nuts replace the hoses, but it's not totally necessary. Replace the 30+ year old drier with a new one, the desiccant is no doubt saturated. Don't mess with the drier until last so as not to expose the desiccant to more moisture than absolutely necessary. Add most of the new oil to the new drier. Put a little oil in the evap and condenser. Probably wouldn't hurt to replace the orifice tube also. Assemble everything with new o rings, go ahead and replace them all, they're cheap. Put your fittings on and draw a vacuum for 30 minutes. Let it set for 10 minutes, it should hold. If it doesn't there's a leak, double check your work. If it holds, charge it up.

Either way:
Get the pressures close, but use them as a guide and use a thermometer in the center vent on recirculate to fine tune. You may find your system works best with the pressures a little off of what would be considered "right". Do it on a warm, 75-85 day, not a scorcher and not a cool one. Put a big fan in front of the grille blowing air through the condenser to simulate driving conditions and prevent high side temp/pressure from going off the chart and causing confusion and unnecessary over tuning. Dig out all the rocks and dirt from the condenser and straighten all the fins. It's tedious but makes a measurable difference in vent temp. Also, don't forget to check simple stuff like making sure the hot/cold blend door is sealing off the hot, or that the recirc door is closing. It's a good time to check the vacuum hoses, check valve, and put the reservoir back on (don't know why people take these off?). Make sure the blower motor has a good power and ground so it's moving as much air as possible.

[v30crewcab]

my truck uses the stock condenser, with a small fan out front, and it will put ice on you, anytime. no need to use anything different. only reason I added the fan was when sitting still it was a little warmer. problem solved.
I flushed mine a long time ago, changed the oil to 134 stuff, and all new o-rings.

[Chevy3+3]

I actually just flushed my entire system, replaced all the orings, replaced orifice tube and charged with oil and 134a today. Todays high temp was about 75-78 degrees I believe. I am running the stock R12 condenser. I charged with 3 cans of 134a. I have a brand new blower motor installed also and it blows hard. My idle temp on Max A/C was about 60-65 degrees but at cruising speed my vent temp was about 52 degrees.

I would really like to see at least 40-45 degree temps. Am I expecting to much???

On this forum someone suggested to use a Ford orifice (blue) and it would work better with 134a. So I did try this and used a blue Ford orifice. I think my low side pressure is around 45-48 lbs and idle

[Desert1957]

Originally Posted by kalbert

The cheap way:
Have any remaining r12 recovered professionally (unless you are equipped do do so). Screw on adapter fittings. Draw vacuum on for 30 minutes. Charge with 134a and an oil charge. Don't expect it to cool very well, don't spread half truths around the Internet about how 134a doesn't work. This was the cheap way, remember?

The "right" way:
Have r12 recovered professionally. Flush the condenser and evaporator to remove any debris and old oil, make sure you get all the flushing solution out. Don't flush the rubber hoses, the tiny amount of mineral oil left in them acts as a barrier. If you want to get nuts replace the hoses, but it's not totally necessary. Replace the 30+ year old drier with a new one, the desiccant is no doubt saturated. Don't mess with the drier until last so as not to expose the desiccant to more moisture than absolutely necessary. Add most of the new oil to the new drier. Put a little oil in the evap and condenser. Probably wouldn't hurt to replace the orifice tube also. Assemble everything with new o rings, go ahead and replace them all, they're cheap. Put your fittings on and draw a vacuum for 30 minutes. Let it set for 10 minutes, it should hold. If it doesn't there's a leak, double check your work. If it holds, charge it up.

Either way:
Get the pressures close, but use them as a guide and use a thermometer in the center vent on recirculate to fine tune. You may find your system works best with the pressures a little off of what would be considered "right". Do it on a warm, 75-85 day, not a scorcher and not a cool one. Put a big fan in front of the grille blowing air through the condenser to simulate driving conditions and prevent high side temp/pressure from going off the chart and causing confusion and unnecessary over tuning. Dig out all the rocks and dirt from the condenser and straighten all the fins. It's tedious but makes a measurable difference in vent temp. Also, don't forget to check simple stuff like making sure the hot/cold blend door is sealing off the hot, or that the recirc door is closing. It's a good time to check the vacuum hoses, check valve, and put the reservoir back on (don't know why people take these off?). Make sure the blower motor has a good power and ground so it's moving as much air as possible.

Thank You for posting the most accurate explanation of what needs to be done to your A/C system. Hopefully this will end the controversy for good.

Desert

[Keith Seymore]

Originally Posted by kalbert

The cheap way:
Have any remaining r12 recovered professionally (unless you are equipped do do so). Screw on adapter fittings. Draw vacuum on for 30 minutes. Charge with 134a and an oil charge. Don't expect it to cool very well, don't spread half truths around the Internet about how 134a doesn't work. This was the cheap way, remember?

The "right" way:
Have r12 recovered professionally. Flush the condenser and evaporator to remove any debris and old oil, make sure you get all the flushing solution out. Don't flush the rubber hoses, the tiny amount of mineral oil left in them acts as a barrier. If you want to get nuts replace the hoses, but it's not totally necessary. Replace the 30+ year old drier with a new one, the desiccant is no doubt saturated. Don't mess with the drier until last so as not to expose the desiccant to more moisture than absolutely necessary. Add most of the new oil to the new drier. Put a little oil in the evap and condenser. Probably wouldn't hurt to replace the orifice tube also. Assemble everything with new o rings, go ahead and replace them all, they're cheap. Put your fittings on and draw a vacuum for 30 minutes. Let it set for 10 minutes, it should hold. If it doesn't there's a leak, double check your work. If it holds, charge it up.

Either way:
Get the pressures close, but use them as a guide and use a thermometer in the center vent on recirculate to fine tune. You may find your system works best with the pressures a little off of what would be considered "right". Do it on a warm, 75-85 day, not a scorcher and not a cool one. Put a big fan in front of the grille blowing air through the condenser to simulate driving conditions and prevent high side temp/pressure from going off the chart and causing confusion and unnecessary over tuning. Dig out all the rocks and dirt from the condenser and straighten all the fins. It's tedious but makes a measurable difference in vent temp. Also, don't forget to check simple stuff like making sure the hot/cold blend door is sealing off the hot, or that the recirc door is closing. It's a good time to check the vacuum hoses, check valve, and put the reservoir back on (don't know why people take these off?). Make sure the blower motor has a good power and ground so it's moving as much air as possible.

x2. Thank you. I'm ready for the "pull a vacuum and recharge" part, hopefully today.

K

[Keith Seymore]

Originally Posted by kalbert

Replace the 30+ year old drier with a new one, the desiccant is no doubt saturated. Don't mess with the drier until last so as not to expose the desiccant to more moisture than absolutely necessary.

For educational purposes: what is the failure mode of having moisture in the desiccant/drier? Does it freeze under heavy duty use and cause problems?

K

[kalbert]

Originally Posted by Keith Seymore

For educational purposes: what is the failure mode of having moisture in the desiccant/drier? Does it freeze under heavy duty use and cause problems?

K

When you suck a vaccum you get most/all of the air out but some moisture gets left behind. The dessicant is supposed to soak the rest up so it isn't circulating either. Since air and water don't boil the same as the refrigerant they are just in the way and taking up space that could be occupied by stuff that will. If the system is left open (or empty) chances are the dessicant is saturated and no matter what you do there will be moisture circulating. Then the pressures won't ever be quite right, and despite your best fine tuning efforts it will be cool bit not cold, because there's water in there that's not taking heat off the evaporator anywhere near as good as the refrigerant does.

Its another one of those 2° tricks that alone isn't much but you add that 2° with the 2° you get from straightening all the condenser fins and the 2° you get from this or that and you're seeing the difference between cool and cold.

[Keith Seymore]

Understood; thank you -

K

[gchemist]

Here is a writup for our trucks. Doing it the "right way" is best. I did it plus upgraded the hoses. The R134 molecule is smaller than R12. Over time, it will leech out of stock R12 hoses. R134 hoses have a barrier between inner and outter walls.

I won't argue with an A/C expert. Air flow across the condensor is important for cooling. Especially a low speeds. A R134 condensor will cooler better at low speeds or idle than an R12 condensor. The multicross flow tubes work better.

[bnoon]

Just keep in mind, "best" will get you a degree or two temperature drop at the vent at best and you will spend 10 times as much.

[SCOTI]

Originally Posted by bnoon

Just keep in mind, "best" will get you a degree or two temperature drop at the vent at best and you will spend 10 times as much.

This was exactly the point of the guy @ the place that builds the custom radiators & condensers.... He said if I was ok w/spending the extra $$ for possibly (possibly) only a 1-2° difference in temp @ the vents, he would take it & build whatever I wanted. He just wanted to be up front.

I did purchase one when swapping parts on my dually project but it was strictly to be starting w/something that was 100% new (clean & straight, unobstructed fins) but I just went w/a OE replacement for ease of installation.

I also optimized the placement of the oil & trans coolers as well to minimize the impact of 'dirty' airflow to the condenser vs how it was set-up from the factory.

[Chevy3+3]

Originally Posted by SCOTI

This was exactly the point of the guy @ the place that builds the custom radiators & condensers.... He said if I was ok w/spending the extra $$ for possibly (possibly) only a 1-2° difference in temp @ the vents, he would take it & build whatever I wanted. He just wanted to be up front.

I did purchase one when swapping parts on my dually project but it was strictly to be starting w/something that was 100% new (clean & straight, unobstructed fins) but I just went w/a OE replacement for ease of installation.

I also optimized the placement of the oil & trans coolers as well to minimize the impact of 'dirty' airflow to the condenser vs how it was set-up from the factory.

So you replaced your condenser with a OEM style for r12 and charged your system with 134a? How cold is your vent temp in your crew? Will it freeze you out?

[SCOTI]

Originally Posted by Chevy3+3

So you replaced your condenser with a OEM style for r12 and charged your system with 134a? How cold is your vent temp in your crew? Will it freeze you out?

Haven't driven it long enough to worry about that. My 90 swb was done the same way though..... I typically drive around w/the fan on lower speeds & the young ladies usually turn the vent away to keep the airflow from hitting them directly so it cools well. I would have to put a gauge on it before I could give you an accurate discharge temp.

[68longhorn]

Originally Posted by SCOTI

Haven't driven it long enough to worry about that. My 90 swb was done the same way though..... I typically drive around w/the fan on lower speeds & the young ladies usually turn the vent away to keep the airflow from hitting them directly so it cools well. I would have to put a gauge on it before I could give you an accurate discharge temp.

My wife always is closing the vents on the passenger side. I can't get enough. lol

[kalbert]

Originally Posted by bnoon

Just keep in mind, "best" will get you a degree or two temperature drop at the vent at best and you will spend 10 times as much.

The best way noted above will be capable of vent temps around 40-45 on a warm-hot day rolling 15mph+. On a scorching day or in traffic with no airflow closer to 50, on a cooler day closer to 40. The coldest you can expect from the cheap way will be around 50 and go up from there. The difference between 45 and 50 is the difference between freezing you out vs thinking it's not working.

One thing I forgot to note, the compressor has to be up to the task. A 30 year old compressor that has been run on a low charge for half it's life probably won't be able to build high enough pressure to make the difference great enough. Unfortunately the only way to test the compressor is to charge the system and see what it can do.

[bnoon]

Originally Posted by kalbert

The best way noted above will be capable of vent temps around 40-45 on a warm-hot day rolling 15mph+. On a scorching day or in traffic with no airflow closer to 50, on a cooler day closer to 40. The coldest you can expect from the cheap way will be around 50 and go up from there. The difference between 45 and 50 is the difference between freezing you out vs thinking it's not working.

One thing I forgot to note, the compressor has to be up to the task. A 30 year old compressor that has been run on a low charge for half it's life probably won't be able to build high enough pressure to make the difference great enough. Unfortunately the only way to test the compressor is to charge the system and see what it can do.

I was within 1 degree vent temps from fully functioning R12 vs 134 with nothing more than the fittings, oil, and charge on a 100 degree day. The AC on my '86 was ice cold at idle too. 43 vs. 44 degrees.

[68longhorn]

I had a compressor go bad a 2 years ago, I work at a shop and evacuated the r12 out but I did not get enough out to do a recharge so I went to r134. I replaced the compressor, old one had a screaming bearing, and nothing else. I pulled a vacuum on the system for 30 minutes and then charged it with about 90% of a full charge, I was told to do this because of the higher pressures r134 operates at. Since than the only downside I have noticed is it takes a minute or 2 longer to initially cool the cab. Other than that it still blows just as cold. I work at a ford dealer and think my ac will out cool a number of newer vehicles. I replaced only the o rings at the compressor, added oil to the new compressor and the retrofit fittings.