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Air conditioning woes

For some time now my air conditioning has been warmer than it should be. So yesterday I bought a bottle of STP refill and the trigger gauge thingy. So I checked the pressure as per the instructions and it said it was a little low. So I refilled the system, again as per the instructions and all was well for half an hour or so, lovely and cold. But then all coldness ceased and when I checked the pressure (on the low side as that is all I can check) The pressure was so high it'd gone off the gauge! Also, I let a little vent (not much as I know it is a greenhouse gas) to see if I could reduce the pressure expecting what came out to be icy cold but there was no coldness at all, just warm air mixed with what I guess is the leek fluid additive in the refrigerant. All a bit weird really, not at all what I was expecting!
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I'm not sure if this is anything that may sound familiar to you, but when I bought my Alfa, whilst doing some of the general fixes I wanted to do I noticed a rubber aircon pipe had been cut. I got a replacement pipe and fitted it myself. I took it for a regas where they tested the vacuum pressure and all was airtight so they regassed the system. When running the system and checking their work the air was not that cold and my gas pressure went round their gauge and they blew another rubber pipe. They told me it was a compressor fault in their ignorance!!

Taking the car to an air-con specialist I told them the tale and left them to check the system. It turned out to be the filter on the side of the condenser (all bolted to the front of the radiator). If there's a leak and this filter comes into contact with 'normal air' the filter stuff becomes solid blocking the gas flow round the system (causing pressure increase). Having a read around the active part of the filter only needs to be in contact with 'normal air for 6 hours max and it's gone solid.

So, could you have had a leak at some point? if so it could be the condenser filter that's blocked. If so it's a new condenser I'm afraid (they got a new one for 100) and a fit (160) and a regas (40). But the aircon is spot on, nice and cold!!
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I'm going to do a proper aircon thread soon. I've fixed the GTA (here: Alfa GTA Sportwagon - Page 1 - Readers' Cars - PistonHeads).

I would be very careful of using those cans in a partially filled system. Reading pressure is a bit of a wild goose chase - it will vary wildly with temperature, and the real metric is weight, the system takes 550g of gas, if you shove more in, then you may be overfilling. That said, when presented with an empty system that passes a vacuum test, I'd have no hesitation in throwing a can in, they're almost exactly the right size.

Bonkers pressure in the low side suggests the compressor is not engaging. There are a number of reasons for this. It could be electrical, as mine was - the system was saying "all good, start the compressor" - but the clutch was not engaging. Thus all the gas sits on the low side. The compressor is also protected by a pressure sensor. If the pressure is too low, it doesn't run. If the pressure is too high (on the output from the compressor) it doesn't run. The hose blowing example above should not happen - the compressor should lock out. Though previous owners may have bypassed the switch.....

My commuting 156 V6 has had no aircon for about 4 years. Time to fix it. I've pressurised the system with Nitrogen, and found one leak so far. New hose and condenser on order - the condenser is knacked anyway and on the V6 & GTA, the condenser is the same thing as the drier - I want to change the drier, so I have to change the condenser. I'll stick some photos up with a how-to once we get into it. Bank holiday w/e task....
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I'm going to do a proper aircon thread soon. I've fixed the GTA (here: Alfa GTA Sportwagon - Page 1 - Readers' Cars - PistonHeads).

I would be very careful of using those cans in a partially filled system. Reading pressure is a bit of a wild goose chase - it will vary wildly with temperature, and the real metric is weight, the system takes 550g of gas, if you shove more in, then you may be overfilling. That said, when presented with an empty system that passes a vacuum test, I'd have no hesitation in throwing a can in, they're almost exactly the right size.

Bonkers pressure in the low side suggests the compressor is not engaging. There are a number of reasons for this. It could be electrical, as mine was - the system was saying "all good, start the compressor" - but the clutch was not engaging. Thus all the gas sits on the low side. The compressor is also protected by a pressure sensor. If the pressure is too low, it doesn't run. If the pressure is too high (on the output from the compressor) it doesn't run. The hose blowing example above should not happen - the compressor should lock out. Though previous owners may have bypassed the switch.....

My commuting 156 V6 has had no aircon for about 4 years. Time to fix it. I've pressurised the system with Nitrogen, and found one leak so far. New hose and condenser on order - the condenser is knacked anyway and on the V6 & GTA, the condenser is the same thing as the drier - I want to change the drier, so I have to change the condenser. I'll stick some photos up with a how-to once we get into it. Bank holiday w/e task....
Thanks for that. My compressor is engaging, I could see it spinning and hear it click in. From what I've read since posting this it seems that it could be one of three things: Over full, compressor failure or expansion valve failure. And I'm not entirely sure the compressor sounds too healthy when it's engaged so.......

So if I have to replace the compressor then it's as well to do the condenser and dryer at the same time by which point the price is probably more than I'm willing to spend just for a bit of cold air!!
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If you have lost refrigerant it is possible that some moisture may have entered the system, this will eventually saturate the desiccant in the filter/drier rendering it fairly useless but it will also freeze at the expansion orifice effectively blocking the system and causing it to trip out on the pressure switch (This will then defrost and cycle over again to confuse the unwary)

If the system is basically sound a proper evacuation and recharge with some decent scales is the best way to sort things out, obviously a replacement filter/drier would help but I've restored the A/C on 3 of my Alfas now by simply recharging properly...nice cool air afterwards and cycling around 40 Psig on the LP switch.

Sprint - 33 - Sprint - 33 - 155 - GTV - GTV - 156 - GT ...gone German for now though.
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Thanks for that. My compressor is engaging, I could see it spinning and hear it click in. From what I've read since posting this it seems that it could be one of three things: Over full, compressor failure or expansion valve failure. And I'm not entirely sure the compressor sounds too healthy when it's engaged so.......

So if I have to replace the compressor then it's as well to do the condenser and dryer at the same time by which point the price is probably more than I'm willing to spend just for a bit of cold air!!
Condenser/dryer is about 80 - not much compared to a compressor! ECP have them. Bumper off job to replace though.

Compressor engaging is a good sign (means that the electronics are working), you need to have a look at the high side to see what is going on. If compressor engages, high side remains low and low side remains high, suggests compressor is knackered. If high side goes high, then you are probably looking for expansion / evaporator problems. The other trick is that occasionally the fan ducting pushes hot air into the air con duct. So the air con and the heater fight each other, you get warm-ish air! (does it make any difference if the engine is stone cold?)
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Condenser/dryer is about 80 - not much compared to a compressor! ECP have them. Bumper off job to replace though.

Compressor engaging is a good sign (means that the electronics are working), you need to have a look at the high side to see what is going on. If compressor engages, high side remains low and low side remains high, suggests compressor is knackered. If high side goes high, then you are probably looking for expansion / evaporator problems. The other trick is that occasionally the fan ducting pushes hot air into the air con duct. So the air con and the heater fight each other, you get warm-ish air! (does it make any difference if the engine is stone cold?)
No still the same if engine is cold.

Sounds like next step would be to get a proper evacuation and recharge and see what happens. I'll give it some thought. I have a mate with the equipment who might be willing to help or I might buy the equipment........decisions decisions. Thank you for your advice guys.
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I thought the compressor wouldn't engage unless the system pressure was within range, +1 on the Dryer, they are supposed to be changed every second re-charge even on a sealed system.
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If you have lost refrigerant it is possible that some moisture may have entered the system, this will eventually saturate the desiccant in the filter/drier rendering it fairly useless but it will also freeze at the expansion orifice effectively blocking the system and causing it to trip out on the pressure switch (This will then defrost and cycle over again to confuse the unwary)

If the system is basically sound a proper evacuation and recharge with some decent scales is the best way to sort things out, obviously a replacement filter/drier would help but I've restored the A/C on 3 of my Alfas now by simply recharging properly...nice cool air afterwards and cycling around 40 Psig on the LP switch.
Did you add any lubrication to the system?
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Did you add any lubrication to the system?
I did add a small amount of PAG-46, though I have to confess to guesstimating the amount based on previous experience (I used to be a commercial refrigeration engineer and used to get asked to do the odd car here and there, originally blowing R12 into old Jags etc )
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I did add a small amount of PAG-46, though I have to confess to guesstimating the amount based on previous experience (I used to be a commercial refrigeration engineer and used to get asked to do the odd car here and there, originally blowing R12 into old Jags etc )
How are you meant to measure the oil? I think it is 25 ml from empty .... but how are you meant to work out what is in there already? The gas is easy - there is none in there when the system is under vacuum, so you put the right amount in. The oil seems to be a bit of voodoo!
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I'm not sure whether this will be any help, but in my 156 I had to change a bulb in the fuel guage. While I had the centre dash apart I noticed that the fan on the interior temperature sensor was covered in fluff, so I cleaned it up. Result was aircon blowing much colder than before at no cost. I've had the car for 7 years and not regassed the aircon, so I was happy with that.
Just a thought, it might be a sensor fault if the compressor is kicking in but there's not much noticeable change in cold air.
It could also be a failure in the motorised flaps that control hot/cold airflow. You can hear them move if you change the settings before starting the car or disconnect and reconnect the battery.
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How are you meant to measure the oil? I think it is 25 ml from empty .... but how are you meant to work out what is in there already? The gas is easy - there is none in there when the system is under vacuum, so you put the right amount in. The oil seems to be a bit of voodoo!
Voodoo sounds about right! I had replaced a couple of blown hoses on my 156 and had blown the system through with nitrogen while open which blew a fair bit of oil out of the open ends under the radiator, I reasoned that the oil charge is not quite as critical as the refrigerant and simply added the recommended full dose...worked fine while I had the car thereafter.

The current GT needed recharging but all hoses were fine when inspected, so I assumed some gas may have been lost through the compressor shaft seal as the previous owner confessed to not liking A/C and rarely used it...I never added any oil in this case as there was no theoretical loss, that was last September and its still blowing icy cold now (I can't quite believe it myself, a 12 y/o Alfa with fully functioning climate control!)
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So, apropos this thread, an interesting development. 12.5 kilos of R134a delivered to my door, for, er, not a lot more than the price of one of those cans from Halfords. All quite legit and above board. That will keep my fleet sorted for about 20 years! I'll need a set of scales now.

For those who are interested, this stuff is perfectly legal to buy as long as you are an end user, and you are going to use it solely on mobile air con systems.
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So, apropos this thread, an interesting development. 12.5 kilos of R134a delivered to my door, for, er, not a lot more than the price of one of those cans from Halfords. All quite legit and above board. That will keep my fleet sorted for about 20 years! I'll need a set of scales now.

For those who are interested, this stuff is perfectly legal to buy as long as you are an end user, and you are going to use it solely on mobile air con systems.
I was quite surprised at this as the F-Gas regulations normally forbid the selling of refrigerant to non-qualified people via wholesalers these days. The F-Gas course is usually a 3 day theory/practical affair costing around 750 or so per individual. When I was selling refrigerant this was strictly enforced, the computer basically would not issue a sale without formal proof of qualification and the good old days of cash sales through the back door have dried up as rogue/non trackable cylinders have become scarcer in recent times.
We were regularly audited by BOC and every cylinder accounted for via barcodes, not a bad thing I suppose but the one man band firms and occasional casual buyers using low volumes of gas didn't think much of it.

It appears that DEFRA have allowed a loophole allowing virtually anyone to purchase R134a if the stated purpose is for use in various types of vehicle (18 classified types) thus allowing garages etc to operate their "one button" A/C diagnostic/recovery/charge machines without conforming to the draconian legislation the rest of the AC&R industry now face...this seems to have caused some upset and is now being investigated so best buy your R134a soon?

How times have changed, when I started it was normally a straight choice of R12, R22 or R502...we used to use R11 for cleaning our tools or the floor (brilliant solvent that boils at about 24 degrees C....tricky stuff if burnt though as it breaks down to form phosgene gas which can be lethal aside from giving you a headache)
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I suppose for once someone sensible drafted the legislation.

If someone is going to be slapdash about it, they will, and all the training in the world won't stop them. Some people will dump this stuff to atmosphere and not give a monkeys. Not many people will buy big cylinders - they're, well, big, and the kit required to connect them is more expensive that getting the job done at a garage.

The 39 cans in Halfords are more of a worry - they seem to be designed for people to shoot into systems with no tools and no ability to find leaks. Some of them will work, but I'd guess a significant number are just vented immediately.
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Today I got the nice guy who services our works air-conditioning to check my car out. Sadly, it seems my compressor has given up the fight. So it seems I maybe able to get a new one on eBay for 150 unless any of you lovely people know anywhere cheaper? Long shot I know as this seems quite a good price.
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