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Attention A/C Experts

S

stephenspann27

NAXJA Forum User
Location
College Station, Tx
So tonight I decided to charge my XJ with 134A. I do not know the A/C history. There was zero charge in the XJ when I got it, and it doesn't look like anyone has ever used 134A in it (no labels or 134A fittings). I pulled vacuum on it and it only held for about 15 mins. I have one of those UV lights.. so in order to find the leak, I first charged the system with a UV 134A can, then a PAG oil can, ( already poured a little PAG oil into the top of the compressor) Some of the first can went in, but not enough pressure built to turn the compressor on. I hooked up my high side hose to monitor the head pressure, then jumped the A/C clutch to the battery, and it sucked the can down in no time. The second can when in much slower.. The compressor still will not come on, on its own. It blew nice cold air while it I was charging it, and the low pressure hose was sweating nicely.

The strange thing is that the head pressure was really low the whole time, like 45psi, shoudln't it be in the 100's?

Anyone know much about how the how the compressor is activated? On most cars, when you put the A/C control on "max" then a signal is sent to turn the compressor on, but on some vehicles, the compressor will not turn on unless the miniumum pressure is met, if it is met, the compressor comes on and it runs untill the high side line pressure gets too high, when it gets two high, the pressure switch deativates the compressor, as the head pressure decreases (due to yoru fan pull the hot air out of the condensor) the pressure switch trips (because the pressure is back down to an accepatble level) and the compressor is turned back on.

This is a 1987 model.
 
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If you jumped the compressor to your battery and it will not work otherwise, sounds like electrical problem, or something with your control switch.
 
stephenspann27 said:
So tonight I decided to charge my XJ with 134A. I do not know the A/C history. There was zero charge in the XJ when I got it, and it doesn't look like anyone has ever used 134A in it (no labels or 134A fittings). I pulled vacuum on it and it only held for about 15 mins. I have one of those UV lights.. so in order to find the leak, I first charged the system with a UV 134A can, then a PAG oil can, ( already poured a little PAG oil into the top of the compressor) Some of the first can went in, but not enough pressure built to turn the compressor on. I hooked up my high side hose to monitor the head pressure, then jumped the A/C clutch to the battery, and it sucked the can down in no time. The second can when in much slower.. The compressor still will not come on, on its own. It blew nice cold air while it I was charging it, and the low pressure hose was sweating nicely.

The strange thing is that the head pressure was really low the whole time, like 45psi, shoudln't it be in the 100's?

Anyone know much about how the how the compressor is activated? On most cars, when you put the A/C control on "max" then a signal is sent to turn the compressor on, but on some vehicles, the compressor will not turn on unless the miniumum pressure is met, if it is met, the compressor comes on and it runs untill the high side line pressure gets too high, when it gets two high, the pressure switch deativates the compressor, as the head pressure decreases (due to yoru fan pull the hot air out of the condensor) the pressure switch trips (because the pressure is back down to an accepatble level) and the compressor is turned back on.

This is a 1987 model.
Click to expand...
First off, 87 take R12, if there is any R12 in there and you added 134 it is only a matter time before the system gets eaten alive, the two combined form an acid [at least thats what I've read and been told by regular mechanics]. The conversion, if done, needs to have the system drawn down by vacum for several hours to get the old stuff and it's lube out of it.
Somewhere in the early 90's the systems went to 134a.
 
On mine (2000) the switch on the accumulator bottle is for low pressure. If you jump across the plug, your compressor clutch should kick in to get the initial charge. The FSM will give the value that the switch should kick in at. It will be different than mine as you likely are mechanically set for R12. If it had the R12 fittings, you should have put R12 in it.
 
RichP said:
First off, 87 take R12, if there is any R12 in there and you added 134 it is only a matter time before the system gets eaten alive, the two combined form an acid [at least thats what I've read and been told by regular mechanics]. The conversion, if done, needs to have the system drawn down by vacum for several hours to get the old stuff and it's lube out of it.
Somewhere in the early 90's the systems went to 134a.
Click to expand...

Did you not read my post before you responded? I say in my original post that the system was empty, and that I evacuated the system (puled vacuum). I also said " don't think anyone has ever put 134A in it."
 
stephenspann27 said:
Did you not read my post before you responded? I say in my original post that the system was empty, and that I evacuated the system (puled vacuum). I also said " don't think anyone has ever put 134A in it."
Click to expand...

Probably not, my daughter rousted me out of the sack at 0430, she left her fogs on in her wrangler and even a red top dies after 14 hours of that. I read yours while I was charging her battery from my XJ.
 
I could be mistaken, but don't you need a retrofit kit in order for R-134a to work in a system that previously took R-12? R-134a has different properties as far as density and heat transfer go, so I think you're gonna have problems if you just pump it into a system designed for R-12 without retrofitting it properly. I am not familiar with what the kits are coming with these days, but I'm pretty sure it's at least new seals/o-rings, different oil, and maybe a new orifice tube. I think you need to take this into consideration first.
 
RichP said:
First off, 87 take R12, if there is any R12 in there and you added 134 it is only a matter time before the system gets eaten alive, the two combined form an acid [at least thats what I've read and been told by regular mechanics]. The conversion, if done, needs to have the system drawn down by vacum for several hours to get the old stuff and it's lube out of it.
Somewhere in the early 90's the systems went to 134a.
Click to expand...


he said he pulled a vaccum on it. so all r12 should be out of it. he will be fine.
to do the retro fit right you should replace the expansion valve (orfice tube) put new seals on it and then put the new fittings on it. and put the reccomended oil in it.
sounds like the compressor is fine if you can put 12v to the clutch and it cools.
you may have a bad low pressure switch.

also when the system is completely empty it takes a little while for the r134 to build up to where the compressor will kick in.
 
the only switch in the system you should have (IIRC) is for the low side. It requires a minimal amount of refrigerant to operate, so if the system drew a can and a half, you've got enough for it to be operating now. I would check for continuity across the switch and see if it's closed. If the switch is open, you will need to replace it, if the switch is closed and you still don't have AC, you'll need to investigate why you're not getting power to the clutch coil.



Join Date: Feb 2008
Location: College Station, Tx
Posts: 390


Re: R-12 to r-134a conversion problem
Quote:
Originally Posted by Shorty
http://www.aa1car.com/library/retrofit.htm

Federal law also requires the permanent installation of R134a fittings ...

even if you were sure you were physically able to connect them, you would be breaking the law by introducing R134a into a system with R12 service ports.









Who is going to bust you on that?


ME-- muuhuuahhh
 
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Shorty said:
the only switch in the system you should have (IIRC) is for the low side. It requires a minimal amount of refrigerant to operate, so if the system drew a can and a half, you've got enough for it to be operating now. I would check for continuity across the switch and see if it's closed. If the switch is open, you will need to replace it, if the switch is closed and you still don't have AC, you'll need to investigate why you're not getting power to the clutch coil.



Join Date: Feb 2008
Location: College Station, Tx
Posts: 390


Re: R-12 to r-134a conversion problem
Quote:
Originally Posted by Shorty
http://www.aa1car.com/library/retrofit.htm

Federal law also requires the permanent installation of R134a fittings ...

even if you were sure you were physically able to connect them, you would be breaking the law by introducing R134a into a system with R12 service ports.









Who is going to bust you on that?


ME-- muuhuuahhh
Click to expand...


Thanks for the advice, I'll check the switch out tonight. Maybe the same switch determines if there is enough pressure to activate the compressor, and also determines if the pressure is too high, and cycles the compressor off.
 
You made a big mistake putting the pag oil in. That is what causes the problems. Mixed refrigerants cause high head pressures, but not acid. The different oils are going to cause a problem. If you were going to mix oil, you should have used ester oil. Sorry! Your best bet is to take your compressor off and drain the oil out and flush the system with some type of approved flush agent(many products available). Then recharge with 134a and the amount of oil on your system tag. Do this again in a week or two of heavy ac usage. Might not be a bad idea to do again after the season. If there are any leaks, go ahead and get some 134a compatable o rings for your vehicle and change as many as you are comfortable getting to. Good luck.
 
“Contrary to other information, PAG and POE are both compatible with mineral oil. Many OEMs are recommending that the old mineral oil be left in a system after removal of the R-12. Because HFC-134a will not mix with mineral oil, it is critical that an additional charge of PAG or POE (check with OEM guidelines) be added to the system for proper compressor lubrication. The amount of oil may decrease refrigerant charge since the system will contain twice the original oil charge. Because R-134a refrigerant is not as dense as R-12, it generally requires between 85-90% by weight of the original R-12 charge. Check with OEM recommendations for proper charge amounts..”

http://www.arkema-inc.com/index.cfm?pag=483



"The essence of the conversion is this: If you are currently running R-12, you have two options. First, you can simply evacuate the system, charge with R-134a and PAG oil, and run as is. The lubricant used with R-12 is mineral oil. Mineral oil will not mix with R-134a, and thus you must use PAG oil. The mineral oil does not need to be removed, as it will seek out quiet spots in the system to just sit there. This is actually the recommended OEM retrofit procedure from automobile manufacturers. The second option is to have the system flushed, removing all traces of mineral oil. In this case, you use ester oil (I don't know why, that’s just what is recommended). If you do not flush the system and use ester oil, it will mix with the mineral oil and "spark" in the system, not lubricating the compressor (which will lead to failure)"

http://www.thirdgen.org/retrofitac








It is not the oils that are not compatible with each other. It is that 134A is not compatible with mineral oil, which means that 134A will not carry the mineral oil through the system to lubricate it. As long as you add POE, or PAG oil to the system with the 134A, the 134A will carry the synthetic oil through the system and lubricate it.
 
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good info. to hyjack the thread for a short while.

what is the amount of PAG required in the R134A system. my ac comp grenaded itself and i am replacing it along with the condesor (damaged a little) with junkyard units. i plan on cleaning out the condensor and hoses to ensure no debris. so, how much oil to add to a dry set up?

we now return to your regularly scheduled posting...
 
stephenspann27 said:
“Contrary to other information, PAG and POE are both compatible with mineral oil. Many OEMs are recommending that the old mineral oil be left in a system after removal of the R-12. Because HFC-134a will not mix with mineral oil, it is critical that an additional charge of PAG or POE (check with OEM guidelines) be added to the system for proper compressor lubrication. The amount of oil may decrease refrigerant charge since the system will contain twice the original oil charge. Because R-134a refrigerant is not as dense as R-12, it generally requires between 85-90% by weight of the original R-12 charge. Check with OEM recommendations for proper charge amounts..”

http://www.arkema-inc.com/index.cfm?pag=483



"The essence of the conversion is this: If you are currently running R-12, you have two options. First, you can simply evacuate the system, charge with R-134a and PAG oil, and run as is. The lubricant used with R-12 is mineral oil. Mineral oil will not mix with R-134a, and thus you must use PAG oil. The mineral oil does not need to be removed, as it will seek out quiet spots in the system to just sit there. This is actually the recommended OEM retrofit procedure from automobile manufacturers. The second option is to have the system flushed, removing all traces of mineral oil. In this case, you use ester oil (I don't know why, that’s just what is recommended). If you do not flush the system and use ester oil, it will mix with the mineral oil and "spark" in the system, not lubricating the compressor (which will lead to failure)"

http://www.thirdgen.org/retrofitac








It is not the oils that are not compatible with each other. It is that 134A is not compatible with mineral oil, which means that 134A will not carry the mineral oil through the system to lubricate it. As long as you add POE, or PAG oil to the system with the 134A, the 134A will carry the synthetic oil through the system and lubricate it.
Click to expand...



134a mixes quite well in close coupled systems that operate above 0 degrees fahrenheit. This comes from The American Society of Air conditioning and Refrigeration Engineers (ASHRAE) journal. Unless you have remote condensers such as 50-100 feet or more away or low temp refrigeration, mineral oil will carry with the 134a just fine and mineral oil isn't as hygroscopic as the pag oil. I have not read anything from a reliable source that says pag oil will mix with mineral oil with success. I have read quite the contrary, but manufacturers move very cautiously. They used to think you couldn't use 134a at all with mineral oil, but the industry is slow to stick their neck out and so they are only recently (respectively) beginning to allow it. It may be ok to mix pag with mineral oil, I just haven't read it from an engineering agency or compressor manufacturer. Poe, or ester oil as I called it, is for sure compatible and has been from the start.
 
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Looks like the low pressure switch is bad, it reads 0.00 (or maybe I don't know how to ohm out a switch). The system still cools well today. The head pressure is also good, the reason I was getting the low reading last night is because I didn't have the valve core depressor thing screwed in enough.

What do I need to set my multi meter on to ohm out a switch? I just set it to 20 ohms..
 
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sweet swapped the relays around and the compressor is running now.. .alhtough it hasn't cycled off yet


Which means I have a bad relay that has now been move to a different location.. I need to find a picture of what relays go to what.. my POS haynes manual doens't say.
 
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