Hi all, quick question! I am trying to refill my AC system on my 2008 Citroen Berlingo (M59) but it's going extremely slowly after the initial burst of refrigerant entered. It takes about 30-40s for 1 gram of refrigerant to enter... I need 575 grams of r134a(!). Is it normal for it to take so long? Compressor is building up pressure, then the engine cooling fan engages and the pressure drops. Could it be the fan? I read it's supposed to run at low speed constantly.
I replaced the compressor, condenser, expansion valve and all the tubes/pipes. All leak checked with nitrogen then pulled a vacuum for 2 hours (1 hour vacuum check then vacuuming again for almost 1 hour).
Really slow AC system refill
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ozvtr
- Posts: 821
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Re: Really slow AC system refill
What equipment are you using? Are you using a set of service gauges?
At about 25-30'C recharge bottle should be about 90-100psi(g). System will be at less than 0psi(g) from a vacuum. When you have about 1/2 charge, the system should be close to 80psi(g) or higher. This should happen in about 30-40 seconds. All of this is without the compressor running. Close the valves and cut the bottle from the A/C system. Start the engine and start the A/C. The "low" side should go from about 70-100'C (depends on the temp of the day) down to about 30-40psi(g). Crack the low side valve and SLOWLY add refrigerant until you have completed the correct amount of refrigerant.
You should easily be able to add 25% of a charge to an evacuated system. That should be enough to kick the A/C on.
You need a pressure differential between the system and the refrigerant bottle to get the refrigerant out. If the refrigerant wont come out either the system and the bottle are at the same pressure or there is a blockage. If the bottle and the system are at the same pressure you need to find out why. Either the refrigerant bottle is exhausted or you are filling from the "high" side with the compressor running...don't do that!
The low side pressure (in a serviceable system) will go down to between 30-40psi(g) while the compressor is running. The high side may range between 150-250 psi(g) depending on the day (hotter=higher pressure).
When the compressor stops running, both pressures will head to between 70-100psi(g), again depending on the day.
At about 25-30'C recharge bottle should be about 90-100psi(g). System will be at less than 0psi(g) from a vacuum. When you have about 1/2 charge, the system should be close to 80psi(g) or higher. This should happen in about 30-40 seconds. All of this is without the compressor running. Close the valves and cut the bottle from the A/C system. Start the engine and start the A/C. The "low" side should go from about 70-100'C (depends on the temp of the day) down to about 30-40psi(g). Crack the low side valve and SLOWLY add refrigerant until you have completed the correct amount of refrigerant.
You should easily be able to add 25% of a charge to an evacuated system. That should be enough to kick the A/C on.
You need a pressure differential between the system and the refrigerant bottle to get the refrigerant out. If the refrigerant wont come out either the system and the bottle are at the same pressure or there is a blockage. If the bottle and the system are at the same pressure you need to find out why. Either the refrigerant bottle is exhausted or you are filling from the "high" side with the compressor running...don't do that!
The low side pressure (in a serviceable system) will go down to between 30-40psi(g) while the compressor is running. The high side may range between 150-250 psi(g) depending on the day (hotter=higher pressure).
When the compressor stops running, both pressures will head to between 70-100psi(g), again depending on the day.
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Ian_99
- Posts: 20
- Joined: 11 Jul 2025, 20:24
- x 2
Re: Really slow AC system refill
Thanks for the reply!ozvtr wrote: 18 Aug 2025, 09:33 What equipment are you using? Are you using a set of service gauges?
At about 25-30'C recharge bottle should be about 90-100psi(g). System will be at less than 0psi(g) from a vacuum. When you have about 1/2 charge, the system should be close to 80psi(g) or higher. This should happen in about 30-40 seconds. All of this is without the compressor running. Close the valves and cut the bottle from the A/C system. Start the engine and start the A/C. The "low" side should go from about 70-100'C (depends on the temp of the day) down to about 30-40psi(g). Crack the low side valve and SLOWLY add refrigerant until you have completed the correct amount of refrigerant.
You should easily be able to add 25% of a charge to an evacuated system. That should be enough to kick the A/C on.
You need a pressure differential between the system and the refrigerant bottle to get the refrigerant out. If the refrigerant wont come out either the system and the bottle are at the same pressure or there is a blockage. If the bottle and the system are at the same pressure you need to find out why. Either the refrigerant bottle is exhausted or you are filling from the "high" side with the compressor running...don't do that!
The low side pressure (in a serviceable system) will go down to between 30-40psi(g) while the compressor is running. The high side may range between 150-250 psi(g) depending on the day (hotter=higher pressure).
When the compressor stops running, both pressures will head to between 70-100psi(g), again depending on the day.
The refrigerant bottle being low on pressure might make sense it's been used once but it's a 900g bottle so there should be plenty in still... Would warming it up a little bit to up the pressure be okay?
What I found very interesting is that the high side pressure reaches around 15 bar (~220psig) then the engine fan kicks on high and the pressure drops to about 8 bar (~120 psig) and the fan kicks off again. I hooked up my Lexia tool and dug around a bit and found out the fan does not want to spin at low speed, only high. I checked the fan control box and it seems to give out the correct voltages (6.6V on low and 11-12 on high setting), but with the fan hooked up to the control box it drops to 0V on low setting... I'll try hooking up a 6V power supply manually and see what that gives.
Edit: Just tested the fan and it works fine. However the low speed voltage coming from the control box drops straight to 0V when I connect the fan, without the fan connected it's about 10V. Am I safe to assume the control box is (semi) dead?
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Ian_99
- Posts: 20
- Joined: 11 Jul 2025, 20:24
- x 2
Re: Really slow AC system refill
Alright so an important update to this thread.
It seems patience was the answer, the pressure in the r134a bottle was not high enough, as it also had to push up quite high to the manifold. After putting a space heater nearby to blow towards the bottle (that was still showing lots of condensation!) it somewhat helped, but what helped most was to take some breaks in between, let the refrigerant 'settle' in the system and warm the bottle up to give more pressure. Then it went a whole lot faster into the system!
Once finished the pressures were perfectly within range according to the workshop manual and the vent temp at 7.5°C while driving with 21°C ambient.
However should I be worried about some air that could have gotten in? I pulled a vacuum on everything (manifold, hoses, fittings) using a T splitter, but forgot to purge the tiny amount of air between the valve depressor and the valve of the bottle. If it were the whole hose it would become an issue but from what I read this very tiny amount should be negligible?
All in all glad the AC is working for the first time I got this car
It seems patience was the answer, the pressure in the r134a bottle was not high enough, as it also had to push up quite high to the manifold. After putting a space heater nearby to blow towards the bottle (that was still showing lots of condensation!) it somewhat helped, but what helped most was to take some breaks in between, let the refrigerant 'settle' in the system and warm the bottle up to give more pressure. Then it went a whole lot faster into the system!
Once finished the pressures were perfectly within range according to the workshop manual and the vent temp at 7.5°C while driving with 21°C ambient.
However should I be worried about some air that could have gotten in? I pulled a vacuum on everything (manifold, hoses, fittings) using a T splitter, but forgot to purge the tiny amount of air between the valve depressor and the valve of the bottle. If it were the whole hose it would become an issue but from what I read this very tiny amount should be negligible?
All in all glad the AC is working for the first time I got this car
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ozvtr
- Posts: 821
- Joined: 13 Oct 2020, 01:11
- x 230
Re: Really slow AC system refill
You put the A/C on when its 21'C? Ha Ha, I put the heater on! 21'C is a bit too chilly for me to be looking at A/C systems. LOL! That explains why the high side pressures dropped so quickly when the fan cut in.
Look up "vapor pressure" charts for R134a if you want to know what pressure the refrigerant should be at for any particular temperature and vice versa. Its particularly handy if you are filling from a small container. Small containers do not have the thermal mass so the temperature (and consequently the pressure) drops very quickly as you drain it. As I said, you need that pressure differential to get the refrigerant out of the bottle and into the system. If the bottle is getting condensation with an ambient temp of 21'C the bottle is going to be getting very cold and the pressure will be very low. So, as you found out, you will need to warm the bottle.
Hopefully the descant in the receiver dryer will absorb the moisture in that small amount of air. If the ambient air is dry that small amount should be handled by the descant.
Look up "vapor pressure" charts for R134a if you want to know what pressure the refrigerant should be at for any particular temperature and vice versa. Its particularly handy if you are filling from a small container. Small containers do not have the thermal mass so the temperature (and consequently the pressure) drops very quickly as you drain it. As I said, you need that pressure differential to get the refrigerant out of the bottle and into the system. If the bottle is getting condensation with an ambient temp of 21'C the bottle is going to be getting very cold and the pressure will be very low. So, as you found out, you will need to warm the bottle.
Hopefully the descant in the receiver dryer will absorb the moisture in that small amount of air. If the ambient air is dry that small amount should be handled by the descant.