No freon in my AC

I have been researching the steps to changing my Sanden A/C compressor to an on-board air set up. I have read repeatedly that the Sanden is lubricated by the flow of freon. I have not had freon in my system in almost 2 years. That got me thinking:

1. If there is no freon in the system to lubricate, is that distroying the compressor?

2. Could the compressor running with no freon be causing a "hot engine" smell after driving?

I've not heard of or seen any threads in that I can recall about a failed A/C compressor, but hear a lot of people mention their system not working properly and not having freon...so I got curious.

Best thing to do would be to turn on the AC and look at the compressor pulley/clutch assembly. If you see 4 stationary bolt heads (in a square), the clutch is not engaged - that is, the compressor is not running.

If there is a very low charge (or no refrigerant at all), the compressor should not run.

Cottontail said:

I've not heard of or seen any threads in that I can recall about a failed A/C compressor, but hear a lot of people mention their system not working properly and not having freon...so I got curious.

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I had one.

http://www.naxja.org/forum/showthread.php?t=954436

Anthrax is right. If you're low, the compressor should *not* engage. Check it and make sure.

There is also oil (called PAG oil) in the system to lubricate it as well.

There's a low pressure cut off switch that's supposed to activate when the pressure of the system gets too low. This prevents the compressor from coming on and being damaged from lack of freon and/or oil. Same goes for if the pressure is too high (if someone has overfilled the system), there is a high pressure cut off switch to keep the compressor from cycling on.

If the compressor is running when it shouldn't be running (say, if the low pressure switch isn't working properly), you should notice a type of burning smell. At least, on the WJ I worked on a couple years ago I did. For some reason it was letting the compressor come on when there was little to no freon in the system.

UNCC_99XJ said:

If the compressor is running when it shouldn't be running (say, if the low pressure switch isn't working properly), you should notice a type of burning smell. At least, on the WJ I worked on a couple years ago I did. For some reason it was letting the compressor come on when there was little to no freon in the system.

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Do you notice that smell during driving, or is it pretty much just an odor after shutting off? I have a hot/burning smell after shutting off. I don't notice it much outdoors where there is a lot of fresh air to disipate, but is it prevelant when I park in the garage.

The compressor does not run with the AC off. You may have a bearing going bad, A/C clutch bearing, Water pump, idler bearing, alternator bearing, power steering, or just a valve cover leak on to the exhaust, wire overheating ......lots of possibilities.

The oil in the compressor lubes the compressor. The oil should be drained and replaced before switching it to use for compressed air, if that is what you were asking.

Ecomike said:

The oil in the compressor lubes the compressor. The oil should be drained and replaced before switching it to use for compressed air, if that is what you were asking.

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That is the first time I have heard that. Every piece of research I have done indicates that only freon lubricates the compressor which is why you need to add an in-line oiler before using it for OBA.

Cottontail said:

Do you notice that smell during driving, or is it pretty much just an odor after shutting off? I have a hot/burning smell after shutting off. I don't notice it much outdoors where there is a lot of fresh air to disipate, but is it prevelant when I park in the garage.

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Nope. When everything's working fine, I don't smell it at all.

I have to wonder if it's something else, such as the bearing in your alternator!

In line oilers are usually used to lubricate a down stream tool, like an air impact wrench. What all do you people use the air for? (I am not an offroad guy)

Freon (a CFC) was outlawed in 1987 (Montreal protocol), and last used around 1992 in new cars in the USA, when OEMs switched to R-134a refrigerant (HFC). Neither was ever a lubricant, but was used as a solvent, and a refrigerant, among other things. The Freon systems used mineral oil in the crank case, which mixed with the Freon and circulated as a mix through out the entire system. Most of the oil was in the crankcase (at least initially), and about another 20-50% in the condenser mixed with the bulk of the liquid freon. The R-134-a systems used mostly PAG oils, which are not good for atmospheric air compressor use, as they are hygroscopic (they suck water out of the air, leading to corrosion).

Air is not a solvent to mineral oil, not in an air compressor. But you will need to top off the crankcase oil periodically, just like the gas engine, as very small amounts of oil do blow by with the produced compressed air. How often? Depends on use, hours of run time. I have a vacuum pump I bought 25 years ago for AC work, still has the original oil in it.

UNCC_99XJ said:

I have to wonder if it's something else, such as the bearing in your alternator!

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Do you think my alternator is going bad? :repair: What on earth would lead you to that conclusion? :dunno:

Ecomike said:

Freon (a CFC) was outlawed in 1987 (Montreal protocol), and last used around 1992 in new cars in the USA, when OEMs switched to R-134a refrigerant (HFC). Neither was ever a lubricant, but was used as a solvent, and a refrigerant, among other things.

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I guess I am using the 2 words innerchangably. The research I have seen shows to put an inline oiler into the new plumbing to lubricate the compressor, and yes, it is an inline oiler like used on air driven tools, like the air impact wrench you suggest.

There is an "arguement" as to if an inline or a mist oiler is more affective or necessary than the other for this kind of application. Most of the reserach I have done, the owners have set up the compressor to fill a 2-3 gallon tank located in the back of the Jeep, mostly for the purpose of airing up tires after runs, but also for use of some air tools.

Thanks for the replies Ecomike. I'm all about learning everything I can before tackling a project.

Cottontail said:

That is the first time I have heard that. Every piece of research I have done indicates that only freon lubricates the compressor which is why you need to add an in-line oiler before using it for OBA.

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As I understand it, In most refrigeration systems some oil circulates with the refrigerant, so if you run the compressor as an open-ended system it will gradually pump out its oil. I've seen a few writeups on this and it is possible to re-rig the Sanden and its ilk to run as an open compressor, but I think you may need some kind of separator on the output to catch the oil if you're using it for inflation.

Matthew Currie said:

As I understand it, In most refrigeration systems some oil circulates with the refrigerant, so if you run the compressor as an open-ended system it will gradually pump out its oil. I've seen a few writeups on this and it is possible to re-rig the Sanden and its ilk to run as an open compressor, but I think you may need some kind of separator on the output to catch the oil if you're using it for inflation.

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I was thinking about the oil in the tires issue as well, but forgot to mention it. Air compressors do not use in line oilers, they self lubricate internally, just like a gas or diesel engine. I think the refrigerated systems circulate the oil because the oil is soluble in the refrigerants, and so they add extra oil, and let it circulate. I would not oil mixed with the air going into my tires.

I recall now, that the rock climbers, lower tire pressure for climbing, then need air pressure to raise the pressure for the trip home.

Ecomike said:

I was thinking about the oil in the tires issue as well, but forgot to mention it. Air compressors do not use in line oilers, they self lubricate internally, just like a gas or diesel engine. I think the refrigerated systems circulate the oil because the oil is soluble in the refrigerants, and so they add extra oil, and let it circulate. I would not oil mixed with the air going into my tires.

I recall now, that the rock climbers, lower tire pressure for climbing, then need air pressure to raise the pressure for the trip home.

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From what I've read it isn't much oil, and can be separated, but it's something you'd need to address. The old vertical piston York compressors were apparently much easier to set up. I had a three of those (ex old Mercedes) and took them once years ago to a NAC barbecue at Eagle's place in Connecticut and they were snapped up like chum in a shark pool.

OK, new to this forum so before stating my big problem with AC, I first would like to say HI to everyone. I have taken my jeep (2000 Cherokee, 6 cyl, automatic) to the AC mechanic who has drawn a vacuum and filled with the OEM amount of freon. Unit works fine with 40 degree air for about 3 to 4 weeks then no freon. Have check with electronic sensor and found no leaks. This has happen twice since I owned the Jeep. Anyone have any ideas where the freon is going? By the way, it looks as if the previous owner replaced the compressor.

UV dye

bngthmpsn said:

OK, new to this forum so before stating my big problem with AC, I first would like to say HI to everyone. I have taken my jeep (2000 Cherokee, 6 cyl, automatic) to the AC mechanic who has drawn a vacuum and filled with the OEM amount of freon. Unit works fine with 40 degree air for about 3 to 4 weeks then no freon. Have check with electronic sensor and found no leaks. This has happen twice since I owned the Jeep. Anyone have any ideas where the freon is going? By the way, it looks as if the previous owner replaced the compressor.

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When they draw a vacuum, usually you shut off the pump and wait 30 minutes to see if the system holds. Your mech can put in a small charge with Dye, then if the pressure drops again he can use UV goggles or light to find the Dye and thus the leak. I suggest having some dye put in this time round.

Very slow leaks are very hard to find, especially a slow front shaft seal leak, or hard to reach and see places. UV die has it limits. My last leak was near impossible to locate, I had been doing AC work for 30 years. I took it to a friend and learned something new. He fired it up, put in a little refrigerant, enough to get the system up to normal pressure, then turned it all off, and waited a few minutes (A/C and engine all off), then he put the electronic leak detector on max sensitivity, like 1 oz per year rate, and he found the two leaks right away. One was the front shaft seal, but UV never showed up there (rotating clutch hid it), the other was the bottom o'ring seals on the expansion valve. With the AC running and fans going it is very hard to find tiny leaks due to the cooling fan running.....