Aircon re-gas

[SirHiss]

I have just been to a garage to get my aircon re-gassed. It ran cold just fine but I've had the car just over 2 years and I have no idea when it was last done so figured it was a good time to get it changed as I had just done full service.

I waited an hour and the tech comes up to me and says it was working before but now it's not. I give him a look of 'well what the fuck do you expect me to say'... He shrugs at me then goes back to my car and talks to another mechanic. He comes back and asks me if it's a single or dual system. Me knowing jack about air conditioning I said I didn't know. He explains that some large BMW's have dual aircon systems for the front and rear and the sticker in my engine bay had capacities for both and they assumed the larger one. So they filled my car with 900 (ml?) of refrigerant instead of 450. I was immediately concerned because that sounds like they doubled the pressure in my system. Couldn't that cause a leak?? While waiting I had a quick google and kept coming up with 450 as the aircon capacity and when I got home I checked the sticker in the engine bay and couldn't find any reference of 900. It only said 440 + 10 with some German written around it that I don't understand.

I was not charged for the procedure as he said he initially took 450 out and has put 450 back in. I asked if he meant new refrigerant and he said "some of it will be mixed with new, yeah". Isn't the whole point of an aircon re-gas to replace the old refrigerant with new? I didn't argue as he didn't charge me and I had to leave anyway as it had been an hour and a half at that point.

Was he a muppet? Is there likely any damage? Should I take it to a different place to have it done again?

[80stech]

There is no such thing as re-gassing, the refridgerant(gas) does not wear or get old. They should not have re-charged the A/C if it was working fine and had no leak. I think rear air is about 700g not 900g. and yes, they could have done serious damage by overcharging it. For sure take it somewhere else that is qualified.

[killcrap]

Originally Posted by 80stech

There is no such thing as re-gassing, the refridgerant(gas) does not wear or get old. They should not have re-charged the A/C if it was working fine and had no leak. I think rear air is about 700g not 900g. and yes, they could have done serious damage by overcharging it. For sure take it somewhere else that is qualified.

re-gassing? maybe not a familiar term your used to but i think you could have an idea of what was done.

you are correct that the gas does not wear or get old, but you are forgetting that the gas does escape very slowly over time through the rubber seals in which case a "re-gassing" will be needed.

over charging should not damage the system. The system has a relief valve and if overcharged enough will blow open and release the gas to atmosphere. if the system was overcharged, the system will not work correctly, but it sounds like they corrected the charge amount.

if the system is blowing cold, the performance should still be checked with a set of gauges by monitoring the low side and high side pressures and with a proper working aux cooling fan.

if re-gassing or recharging is needed;

the procedure at a shop that has a recover machine will be to recover the gas and measure the amount removed. The machine should have a multi-pass filtering system to recycle the gas and store it in its internal storage vessel. The ISV will have new refrigerant in it as well.

if the system was empty, then the system should be placed under a deep vacuum to boil off and remove moisture from the system and check for an immediate rise in pressure(a sign of a leak)

If the system still had a small charge in it, it is unlikely any moisture entered the system and a 10 minute vacuum time can be done instead.

If the system is holding the vacuum correctly, you then add oil dye, typically 0.3oz to the system and then recharge(re-gas) the system to the specified amount and then another performance test performed using the gauges and a temperature probe at the vents to compare the saturated temp at the evaporator to the observed temperature at the vent. a 5-15 degree difference is acceptable.

[SirHiss]

Originally Posted by killcrap

re-gassing? maybe not a familiar term your used to but i think you could have an idea of what was done.

you are correct that the gas does not wear or get old, but you are forgetting that the gas does escape very slowly over time through the rubber seals in which case a "re-gassing" will be needed.

over charging should not damage the system. The system has a relief valve and if overcharged enough will blow open and release the gas to atmosphere. if the system was overcharged, the system will not work correctly, but it sounds like they corrected the charge amount.

if the system is blowing cold, the performance should still be checked with a set of gauges by monitoring the low side and high side pressures and with a proper working aux cooling fan.

if re-gassing or recharging is needed;

the procedure at a shop that has a recover machine will be to recover the gas and measure the amount removed. The machine should have a multi-pass filtering system to recycle the gas and store it in its internal storage vessel. The ISV will have new refrigerant in it as well.

if the system was empty, then the system should be placed under a deep vacuum to boil off and remove moisture from the system and check for an immediate rise in pressure(a sign of a leak)

If the system still had a small charge in it, it is unlikely any moisture entered the system and a 10 minute vacuum time can be done instead.

If the system is holding the vacuum correctly, you then add oil dye, typically 0.3oz to the system and then recharge(re-gas) the system to the specified amount and then another performance test performed using the gauges and a temperature probe at the vents to compare the saturated temp at the evaporator to the observed temperature at the vent. a 5-15 degree difference is acceptable.

Thank you for all your technical insight! I Feel better about it now.

[nick325xit 5spd]

Yeah, these system have a high pressure cutoff switch. The AC stopped working because the high side pressure reached the limit and the system cut off. I wouldn't be worried about damage from the overcharging.

And generally, if the AC is performing fine, I wouldn't be bothering with evacuating / recharging it. It's not necessary. While the systems do nominally lose some gas over time, it's a minuscule amount unless something is wrong.