Aircon regas only on high pressure side??

[Pistonpants]

Had my air con regassed at a garage today and they only connected their machine to the high pressure connector. The low pressure connector is in the wheel arch and more fiddly to get to.

When I questioned this they said it was fine and you don't need to connect the low pressure side.

Can't help but think if that was the case their machine (and my car) wouldn't have a low pressure connector.

Would this have done the job properly? If there was a leak in the low pressure system I can't see it would have detected it. Also would it have sucked out all the oil?

Air con had virtually no refrigerant when they tested it and now it is definitely cooler, but not really icy cold.

Was this a bodge job or is it ok to connect the high pressure side only?

Edited by Pistonpants on Thursday 19th April 18:00

[GreenV8S]

I don't know what is normal practice. There is basically a single loop so I don't see any problem filling from the high pressure side only, as long as you fill it to the correct static pressure with the system off. (Filling from the low pressure side might be problematic.)

If you were trying to diagnose problems other than low refrigerant, you'd want to compare pressures on the high and low sides while it was running. It may be good practice to do this as a check after filling too, but I don't know about that.

[Elliot2000]

As above, no issue filling the system just from the high side. High and low is in the same circuit so will still fill the low side

[E-bmw]

It is one loop, basically 2 heat exchangers connected by a compressor, condenser & some pipe, fill it where you like the end result is the same.

[Pistonpants]

Just been for a drive and now blowing warm air so I guess all the gas must have leaked out within a day.

The machine did a vacuum pressure test which it passed, but I assume if the leak is on the low pressure side then it would have missed this.

They said no charge if it spots a leak as they wouldn't waste any freon, but I guess I should get my money back as they didn't connect the low pressure hose which would have most likely failed the pressure test.

[finlo]

Low and high side are not separate, just before and after the compressor.

[Pistonpants]

finlo said:

Low and high side are not separate, just before and after the compressor.

Agreed, but the high pressure side is connected to the low pressure side via a small oriface plate, so when the tester creates a vacuum on the high pressure side I would think the vacuum would not be as strong on the low pressure side so less likely to identify a leak in the 30seconds or so it holds the vacuum for the test.

[GreenV8S]

Pistonpants said:

Agreed, but the high pressure side is connected to the low pressure side via a small oriface plate, so when the tester creates a vacuum on the high pressure side I would think the vacuum would not be as strong on the low pressure side so less likely to identify a leak in the 30seconds or so it holds the vacuum for the test.

I don't agree with your reasoning. The evaporator orifice forms a significant restriction to the refrigerant in its liquid state, but gaseous refrigerant or air will go through it with no trouble.

[Pistonpants]

GreenV8S said:

I don't agree with your reasoning. The evaporator orifice forms a significant restriction to the refrigerant in its liquid state, but gaseous refrigerant or air will go through it with no trouble.

I know very little about this, however would I be correct when the A/C is off the pressure equalises between the low and high pressure side and the refrigerant is in a gaseous state on both sides? If that is the case then when the compressor starts it is able to pressurise the gas against the oriface plate into a liquid and there is a very high pressure differential between both sides. If the gas was able to pass through the oriface plate with no problem/ minimal resistance as you suggest then it would never get pressurised to a liquid state and the pressure would remain roughly equal in both sides.

Edited by Pistonpants on Thursday 19th April 21:27

Edited by Pistonpants on Thursday 19th April 21:28

[Polome]

When the ac compressor is running ( and it needs to be to fully charge system) the HP line i.e. Discharge is at approx 120-150 psi...can't imagine the gas in a stored bottle to recharge system willl be at high enough pressure to get into system....if your ac not cold enough it could be that it has insufficient gas/ oil content. I would speak to an AC specialist and get advice....good luck. Ian

[Pistonpants]

Polome said:

When the ac compressor is running ( and it needs to be to fully charge system) the HP line i.e. Discharge is at approx 120-150 psi...can't imagine the gas in a stored bottle to recharge system willl be at high enough pressure to get into system....if your ac not cold enough it could be that it has insufficient gas/ oil content. I would speak to an AC specialist and get advice....good luck. Ian

The machine they used had an electric pump so should be able to force the gas in, the only thing I'm unsure of is how long it takes for the pressure to equalise between the high and low pressure side. If it's a few seconds then probably it would have filled ok, but if it takes longer the machine would filled to the correct pressure on the high pressure side but then the gas would move to the low pressure side and the pressure would drop resulting in underfilling

[Polome]

From a completely empty system most cars have a listed fill capacity and I suppose the connection done on your car could have had the correct amount injected. The best way to see a systems performance is with an ac rig connected to both hp & lp sides , with compressor readings can be taken to help diagnosis. Good luck