Totally agree, it's a sealed system, if you're loosing gas it has a leak.
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Aircon Discussion
- Thread starter mrdelmonti
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Totally agree, it's a sealed system, if you're loosing gas it has a leak.
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If only it were true. In fact going back pre ozone layer stuff to the days of old refrigerants, you would be closer to the truth. The fact is, unlike a home refrigerator which is sealed, auto air con has a spinning shaft that enters the compressor via a shaft seal.
Since refrigerant R12 (which had a large molecule) was banned, it has been replaced with R134A which has a small molecule, which seeps past the shaft seal in even the newest system free of leaks elsewhere. It is therefore recommended to run your AC for at least 15 minutes a week to keep everything circulating around and the shaft seal lubricated with fridge oil to give it the best chance of holding gas.
If you add to this that the joints are routinely shaken and they have 20 plus year old O rings in them then leaks do appear and often show as slight oilyness around the joints.
The only other areas to service would be checking the condenser adjacent to the radiator is not blocked by debris, and cleaning out the algae and slime from the evaporator coil (cold radiator) in the dash. This is the bit that smells musty when you switch your AC on after a long break. Other service would be checking drains were free of debris and seals intact on any panels removed for inspection.
If only it were true. In fact going back pre ozone layer stuff to the days of old refrigerants, you would be closer to the truth. The fact is, unlike a home refrigerator which is sealed, auto air con has a spinning shaft that enters the compressor via a shaft seal.
Since refrigerant R12 (which had a large molecule) was banned, it has been replaced with R134A which has a small molecule, which seeps past the shaft seal in even the newest system free of leaks elsewhere. It is therefore recommended to run your AC for at least 15 minutes a week to keep everything circulating around and the shaft seal lubricated with fridge oil to give it the best chance of holding gas.
If you add to this that the joints are routinely shaken and they have 20 plus year old O rings in them then leaks do appear and often show as slight oilyness around the joints.
The only other areas to service would be checking the condenser adjacent to the radiator is not blocked by debris, and cleaning out the algae and slime from the evaporator coil (cold radiator) in the dash. This is the bit that smells musty when you switch your AC on after a long break. Other service would be checking drains were free of debris and seals intact on any panels removed for inspection.
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I've had UV dye in my 80 system for 7 years now and no dye has come past the shaft seal so I doubt whether any gas has either. Whenever I've had a drop in pressure I have found a leak which one would not class as a service item. I have a pressure gauge which I pop on the system. I even make sure the air temperature is the same and the car has stood overnight. My 100 has had no drop in pressure in 6 years so I doubt it will start losing pressure without a fault. I've had to regass my 80 3 times but have always found a leak. For what it's worth "Westlands Toyota" Stourbridge have told me they do not service the aircon on the 80.
When my 80 system failed after about 13 years from new I put in UV dye and found 4 leaks. All other joints had no dye. I doubt whether gas can get out without the dye coming out too. These leaks could not have been prevented by any type of service other than stripping and rebuilding.
I agree the system should be used to prevent the shaft seal running dry but if it failed for not running it would not be a service issue. Some cars when started automatically start with the aircon "ON" so that owner negligence in this area is negated.
I'm just rebuilding a pump for my 80 as a spare. The pump makers do not sell seals, not even to pump specialists. They are obliged to sell to the car makers, if required, so I've managed to get genuine shaft seals from Toyota.
When my 80 system failed after about 13 years from new I put in UV dye and found 4 leaks. All other joints had no dye. I doubt whether gas can get out without the dye coming out too. These leaks could not have been prevented by any type of service other than stripping and rebuilding.
I agree the system should be used to prevent the shaft seal running dry but if it failed for not running it would not be a service issue. Some cars when started automatically start with the aircon "ON" so that owner negligence in this area is negated.
I'm just rebuilding a pump for my 80 as a spare. The pump makers do not sell seals, not even to pump specialists. They are obliged to sell to the car makers, if required, so I've managed to get genuine shaft seals from Toyota.
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P.S. Apparently the gas is dissolved in the oil. If you relieve the pressure in the system until no gas comes out, then seal it back up, the system regains quite a lot of pressure from gas still in the oil. It takes a long time for the gas to boil out of the oil completely.
Alas my compressor siezed on the way back from the Adventure Overland Show so looks like I'm going to need to change mine. [emoji22][emoji22][emoji22] the joys of a 21 yr old vehicle.
I'm not sure what size molecule the dye is but it's a fair assumption that it should be the same as the refrigerant.
As you say, no leaks would be fixed as a service item, but there are things that can be done to help any refrigeration system stay healthy.
I'm not sure what size molecule the dye is but it's a fair assumption that it should be the same as the refrigerant.
As you say, no leaks would be fixed as a service item, but there are things that can be done to help any refrigeration system stay healthy.
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No one listens to me on this, but dont forget to put pag oil in your new compressor. Dont let the aircon dude tell you " theres oil in it mate". To the op, welcome to the modern day world of shonk. Where its style over subtance, bs over brains and presentation over practicality. Where after going on a weeks course of multiple answer questions you can become a "tech" or a "engineer" or a "specialist" in whatever youve paid your 800 quid to become..
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Fear not CG. I worked for a refrigeration company for three years and have a rock solid refrigeration engineer that I work with now. I had recently asked him to put more gas and oil in but it beat him to it. There will be an amount of oil the system needs as well as a weight of refrigerant. There's no way the system will be run by me without either.
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I have seen seized compressors before but don't understand how they seize as there is a cut off switch for low gas pressure. Is it that gas was put in but no oil ? Is it your clutch that is seized on to the compressor nose. I've seen that happen giving the impression that the compressor is seized but to test you can still turn the compressor spindle itself. Really bad luck anyway.
Poor Service From Main Dealer
You can get it through hydraulic lock. This would be rare on a vehicle but can occur through poor pipe work design when a slug of oil forms in a low point then gets swept along back to the compressor. Too much oil could cause it or a major leak letting all the oil out. Still, you are right there is an LP (low pressure) cut out switch that works both to cycle the system on temperature (remembering that temperature and pressure are related) and to prevent it running when it's short of gas.
Mine seized as I was driving and I haven't looked at it yet. It went solid and made the clutch slip for the few seconds it took me to turn off the AC. Nasty, smelly!! I will need to check exactly what has gone.
It may be that a leak has lost the oil as it's very difficult to know how much oil is in a small system. Usually a top up is gas only as too much oil can cause a seizure. DIY top up kits contain a small amount of oil so can actually over fill a system with oil.
Not sure what's done mine in but if I find out I'll post it up here.
You can get it through hydraulic lock. This would be rare on a vehicle but can occur through poor pipe work design when a slug of oil forms in a low point then gets swept along back to the compressor. Too much oil could cause it or a major leak letting all the oil out. Still, you are right there is an LP (low pressure) cut out switch that works both to cycle the system on temperature (remembering that temperature and pressure are related) and to prevent it running when it's short of gas.
Mine seized as I was driving and I haven't looked at it yet. It went solid and made the clutch slip for the few seconds it took me to turn off the AC. Nasty, smelly!! I will need to check exactly what has gone.
It may be that a leak has lost the oil as it's very difficult to know how much oil is in a small system. Usually a top up is gas only as too much oil can cause a seizure. DIY top up kits contain a small amount of oil so can actually over fill a system with oil.
Not sure what's done mine in but if I find out I'll post it up here.
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"I have seen seized compressors before but don't understand how they seize as there is a cut off switch for low gas pressure. Is it that gas was put in but no oil ?"
This is what i keep harping on about. The compressor, the dryer, the condensor, should as a rough guide contain 2floz oil each. I replaced most of my system and on getting it regassed i told the fella that id put pag in the components. He replyed they dont bother because the machine does it. " look, it puts 8 grammes in"......
This is what i keep harping on about. The compressor, the dryer, the condensor, should as a rough guide contain 2floz oil each. I replaced most of my system and on getting it regassed i told the fella that id put pag in the components. He replyed they dont bother because the machine does it. " look, it puts 8 grammes in"......
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CG what I don't understand is how to ensure that there is the correct amount of oil in the system. My local air con specialist has a fully automatic machine that evacuates the system then adds the "correct" amount of oil. The question that I cannot find the answer to is " does the evacuation remove all the oil otherwise the machine cannot judge how much to add ? "
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Just talked to the trainer at Motorclimate UK. The machine has to assume that the car has the correct/original amount of oil in. It evacuates the system and removes all the gas and a small amount of oil comes out. This amount of oil is added back during the regass and the status quo is maintained. Unfortunately with old cars which have had a/c parts removed and have been incorrectly gassed there is no way of knowing how much oil is in the system. Therefore when you change your a/c condenser for example you should drain the oil out of the old one and add it back to the system otherwise when you have a regass there will not be enough oil in. When they are in doubt they flush the whole system to remove all the oil then add the correct amount for that car before regassing. There must be room for error because I've changed parts 3 times on mine and must have lost a lot of oil but have not had a seized pump yet.
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it took me a hell of a lot of research to get the same information you got in a 5 min conversation frank!
as you say, the machine doesnt remove the oil on a re-gas, it introduces a very small amount. new components need to be filled with pag 46 to the amount stated in the fsm. 2 floz is a good general rule of thumb for any system. i have said this a number of times when people have fitted new condensers, dryers etc and it has fallen on def ears. maybe because when they go for a re-gas they are told the machine does it automatically. (as i was) it doesnt, 8g was added in my case which is no where near enough, im presuming the operator, tech, engineer, operative, etc etc is taking this as there is enough oil being added to the system.
as you say, the machine doesnt remove the oil on a re-gas, it introduces a very small amount. new components need to be filled with pag 46 to the amount stated in the fsm. 2 floz is a good general rule of thumb for any system. i have said this a number of times when people have fitted new condensers, dryers etc and it has fallen on def ears. maybe because when they go for a re-gas they are told the machine does it automatically. (as i was) it doesnt, 8g was added in my case which is no where near enough, im presuming the operator, tech, engineer, operative, etc etc is taking this as there is enough oil being added to the system.
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CG it took me a hell of a lot of years to get that 5 min conversation with someone who knows the answers 
. I'll be adding oil next time I have a problem to make up for all the oil I've lost. You are right that some people think the machine did it automatically, I did, but when I questioned the last tech' he said it was automatic but could not really answer my questions.
. I'll be adding oil next time I have a problem to make up for all the oil I've lost. You are right that some people think the machine did it automatically, I did, but when I questioned the last tech' he said it was automatic but could not really answer my questions.
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like you say, i also found it difficult getting answers i was satisfied with hence the research.
i never really got to the bottom of how oil sitting in the bottom of the condenser or dryer serves any lubricating duties.
you can add extra oil to the compressor if you want more oil in the system. make sure the compressor wheel is turned by hand a dozen times to avoid it hydrolocking. again how this levels itself out through the system i dont know.
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I think it's quite windy in there and the oil just gets blasted round by the wind.. You can see the oil rushing past the inspection glass window in the pipework. It circulates through the system so when expelled from the compressor more is sucked in by the compressor.
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What you see in the sight glass isn't oil. If you see anything rushing through there it will be gas bubbles in the liquid. It should be full of liquid and appear clear. The only trouble is that clear can mean all gas or all liquid so you need a bit more info to really tell. If you see stuff rushing through, your system is short of gas.
The oil in other parts does nothing, it's simply on its journey around the system and can be added at any point ideally while the system is running and in small amounts. Straight into the compressor suction has to be done carefully to avoid hydraulic lock. I can remember pumping oil into a system against pressure manually which wasn't fun. I'll report back when mine is done.
What you see in the sight glass isn't oil. If you see anything rushing through there it will be gas bubbles in the liquid. It should be full of liquid and appear clear. The only trouble is that clear can mean all gas or all liquid so you need a bit more info to really tell. If you see stuff rushing through, your system is short of gas.
The oil in other parts does nothing, it's simply on its journey around the system and can be added at any point ideally while the system is running and in small amounts. Straight into the compressor suction has to be done carefully to avoid hydraulic lock. I can remember pumping oil into a system against pressure manually which wasn't fun. I'll report back when mine is done.
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Bit confused SC. The only liquid in the system is oil and mine is green with dye. As you say it circulates and I have always been able to see this circulation in the site glass. As in green oil rushing over the sight glass as you describe. There is only gas and silicone oil in a car a/c system. In a new system the oil is clear. I'm full up to gas pressure. I check it regularly.
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Refrigerant exists at low pressure as a gas, compressed and hot as a vapour and condensed as a liquid until it is atomised by the Thermostatic Expansion Valve into the evaporator (like an aerosol) where it cools rapidly to allow it to take in heat where it becomes a gas. Your sight glass is in the liquid line after the condenser and the receiver/filter/drier where it should be fully fed with liquid from the receiver if your system has enough refrigerant in it.
Your gas pressure doesn't indicate the level of refrigerant in the system.
The way to tell if your system is full is to see (in your case) a fully green sight glass with no bubbles. In a system without dye that is very low on refrigerant you would only have gas going through the sight glass which would look empty. A full sight glass without dye also looks clear.
Refrigerant exists at low pressure as a gas, compressed and hot as a vapour and condensed as a liquid until it is atomised by the Thermostatic Expansion Valve into the evaporator (like an aerosol) where it cools rapidly to allow it to take in heat where it becomes a gas. Your sight glass is in the liquid line after the condenser and the receiver/filter/drier where it should be fully fed with liquid from the receiver if your system has enough refrigerant in it.
Your gas pressure doesn't indicate the level of refrigerant in the system.
The way to tell if your system is full is to see (in your case) a fully green sight glass with no bubbles. In a system without dye that is very low on refrigerant you would only have gas going through the sight glass which would look empty. A full sight glass without dye also looks clear.
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