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Author Topic: Aircon regas Q  (Read 619 times)

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Doctor Gollum

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Aircon regas Q
« on: 07 March 2021, 22:46:44 »

The Barge needs its aircon regassing, and according to MB, it requires extra PAG 46 oil added for each component replaced...

20ml for the drier and 10ml for the expansion valve. It also suggests an amount for each line replaced. The lines haven't been replaced but the seals have. Which I suspect amounts to the same thing :-\

The question being, can the regas machine adjust the amount of oil added?

The low pressure return to the compressor has an easily accessible joint to add additional oil. I do have some as I bought a can for lubricating the fresh seals.
« Last Edit: 07 March 2021, 23:03:08 by Doctor Gollum »
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LC0112G

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Re: Aircon regas Q
« Reply #1 on: 08 March 2021, 09:38:26 »

The oil is there to lubricate the only moving part in the system - the compressor. It is miscible with the gas (R134a presumably) which kind of means it dissolves in the gas and then the gas carries it around the system so that there is a steady flow of oil through the compressor pistons. When the gas escapes the oil is left behind and even the vacuuming down of the system before refill will not remove much of it.

The calculations on how much oil to add to the various components when replacing them is based on their volume - the amount of oil that they would normally contain when the system is operating properly. What you must not do is add all the required oil to one point in the system. That would cause a slug of oil in one part which eventually might find it's way into the compressor in one 'lump' and damage it. If you've just replaced the condenser then it's fine to put the right amount into it. Similarly with the expansion valve and drier and the pipes. But if you've replaced several components, make sure you spread the oil around correctly, don't just pump it all in in one location.

The refilling machine can't know which components you have replaced or washed out, so can't add the oil automagically. Some machines do allow you to add extra oil, some don't. Personally I always add the oil myself rather than trust the monkey operating the 'dalek'.
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henryd

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Re: Aircon regas Q
« Reply #2 on: 08 March 2021, 11:54:42 »

Most aircon re-gas equipment can have the pag oil adjusted
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Doctor Gollum

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Re: Aircon regas Q
« Reply #3 on: 08 March 2021, 12:21:07 »

Most aircon re-gas equipment can have the pag oil adjusted
:y
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Re: Aircon regas Q
« Reply #4 on: 08 March 2021, 17:33:43 »

Miscible. Never too old to learn something new.  :y Excellent word added to my vocabulary. Only six more left to go!
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Re: Aircon regas Q
« Reply #5 on: 08 March 2021, 18:10:37 »

Well that went well. Not ;D

Too big a leak to pull a vacuum to do a leak test and add some dye to find the leak...  ::)

Next step would potentially be to re replace all the seals using genuine MB ones so that there's no discrepancy there (I used generic from a selection box matched as best as it possible) and replacing the compressor and condenser. That way, the only unchanged part would be the evaporator. Which would mean also the heater matrix as it's a dash out job...

Sooo... Ho diddly hum pom.
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henryd

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Re: Aircon regas Q
« Reply #6 on: 08 March 2021, 18:19:16 »

Well that went well. Not ;D

Too big a leak to pull a vacuum to do a leak test and add some dye to find the leak...  ::)

Next step would potentially be to re replace all the seals using genuine MB ones so that there's no discrepancy there (I used generic from a selection box matched as best as it possible) and replacing the compressor and condenser. That way, the only unchanged part would be the evaporator. Which would mean also the heater matrix as it's a dash out job...

Sooo... Ho diddly hum pom.

Try and adapt a tyre valve to add some air to system to find the hiss where it's leaking,my money is on the compressor as they are prone to seals failing if left ungassed for long periods

Edit,just seen that you replaced compressor,New part ?
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Re: Aircon regas Q
« Reply #7 on: 08 March 2021, 18:43:11 »

Not yet.

Replaced items so far: Drier, expansion valve and ALL the O rings.

Compressor clutch appears to be working correctly, as best as can be tested ign on/aircon switch on off... Certainly feel a difference when it's engaged, but still smooth with no binding or pulley issues. From what I can gather, the compressor is constantly engaged with a bypass valve regulated by the climate panel.

I did pull the condenser to check both sides, and no evidence of any previous leaks.

It's possible that the new seals, although looked the same as what came out, may be too small/large. I did dip them in Pag 46 before fitting, so it isn't as though they were fitted dry.

Also it's a possibility that the low pressure connection to the compressor and the allen bolts than hold the expansion valve to the evaporator connection aren't quite tight enough but the torque setting is pretty low on the entire system... There's only so much torque you can put through a 3mm allen bolt into aluminium ;)
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STEMO

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Re: Aircon regas Q
« Reply #8 on: 08 March 2021, 18:47:47 »

Good job you're on furlough, that car is a full time 40 hour a week job. ;D
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LC0112G

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Re: Aircon regas Q
« Reply #9 on: 08 March 2021, 19:49:39 »

The correct way to do it is to pressurise the system with dry Nitrogen - up to about 7 bar pressure. If the leak is big enough to prevent vac-down then you should hear it hissing. A proper Air-Con place would know this  ::)

I have also done it using normal compressed air. Trouble is there are reports that R134a + compressed air can be explosive. I don't know what combinations cause the explosive conditions, but I do believe the reports. So do ya feel lucky punk - do ya?  You might want to warn the other residents of Brackley first ;D

My money is on the condenser. It's always the condenser. Even when it's not the condenser, its the condenser.
« Last Edit: 08 March 2021, 19:53:29 by LC0112G »
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Re: Aircon regas Q
« Reply #10 on: 08 March 2021, 21:03:07 »

Nitrogen at 10-20psi,. Get a squirty bottle with a soapy solution in. Pressure the system, spray joints and condenser with solution,, hay presto bubbles= leak. Check check both ports first.
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Re: Aircon regas Q
« Reply #11 on: 08 March 2021, 21:16:30 »

Most aircon re-gas equipment can have the pag oil adjusted

So ... to use Rob's description  ::).... will the 'monkey' operating the machine know how much pag oil to add?
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Andy B

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Re: Aircon regas Q
« Reply #12 on: 08 March 2021, 21:17:57 »

and how do you calculate how much oil to add?  :-\

I ask as I think I'll be doing this on Mrs B's C3 some time soon  :y
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Re: Aircon regas Q
« Reply #13 on: 09 March 2021, 00:29:04 »

They treated it as a complete fill rather than a remove/replace, so oil and refrigerant would have been the original factory amounts :y
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Re: Aircon regas Q
« Reply #14 on: 09 March 2021, 00:36:51 »

Nitrogen at 10-20psi,. Get a squirty bottle with a soapy solution in. Pressure the system, spray joints and condenser with solution,, hay presto bubbles= leak. Check check both ports first.
Ports were both replaced with genuine new last year... because they leaked  ;)

Well that went well. Not ;D

Too big a leak to pull a vacuum to do a leak test and add some dye to find the leak...  ::)

Next step would potentially be to re replace all the seals using genuine MB ones so that there's no discrepancy there (I used generic from a selection box matched as best as it possible) and replacing the compressor and condenser. That way, the only unchanged part would be the evaporator. Which would mean also the heater matrix as it's a dash out job...

Sooo... Ho diddly hum pom.

Try and adapt a tyre valve to add some air to system to find the hiss where it's leaking,my money is on the compressor as they are prone to seals failing if left ungassed for long periods

Edit,just seen that you replaced compressor,New part ?
To further answer your point Henry, there were two oily accumulations, ie black/slimy/minging on the system... one was the condenser connection (where I found evidence of the dye) and tother the compressor itself... although I had dismissed this as residue from oil filter housing seals and rocker cover seals which have both been replaced. :-\
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