A/C System Refill Issues
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jimmy57
- Posts: 6696
- Joined: 12 Nov 2010, 09:25
- Year and Model: 2004 V70R GT, et al
- Location: Ponder Texas
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First: NO A/C CHARGING WITH ENGINE IDLING!!!!! engine speed is too low for compressor to be at 100% capacity. High side will be lower than normal and low side will be higher.
Second: Set system to the standard settings as prescribed by all manufacturers. Fan at next to high speed. Recirculated inside air. Windows closed. Engine at 1200 to 1500 RPM. Let it go for 5 minutes to get stabilized and then worry about pressure readings. If it is definitely low don't wait as the time is not going to change pressure or cool the inside of car if it is no doubt low on charge.
For single evaporator (not an XC90) systems the low side should get to mid 20's after it has cooled the interior down to 75F or lower. Once it gets to mid 20's the evaporator will get cold enough that the thermistor signal will have CCM shut down compressor via signal over CAN to ECM on P2 or on P1 and P80 the pressure cycling switch will interrupt signal to shut off compressor until pressure (and thus temp) rise back to higher level (low 40's). If you have not overfilled the system then turning fan down to lowest speed once the car has cooled down some will make the system cycle compressor quickly but not every 10 seconds. Also, with the car still hot inside the low side line back to compressor will not be so cold. don't be too quick to add more charge if it is not close to freezing cold initially. The heat in car is completely evaporating the refrigerant inside and the chilling effect on that line will not be much. After the car is 75F or lower inside that line should be very chilled then.
The low side pressure will get lower with cooler interior temps as will the high side pressure.
If you are working on any P3 or an XC90(P2) with 3.2 or V8 then you have variable displacement compressor and the elevated engine speed for testing and partial charge still applies but the variable compressor will give you fits with pressures once the car cools down. If a VD compressor car has poor A/C performance the first step is to monitor the VD solenoid signal to see that is is 70% or higher duty cycle. If it is not with a hot car then the evap temp probe or other issues exist. If the signal is high and the low side is not chilling with below normal pressures low and high sides then add a bit of refrigerant to see if it drives pressure towards normal to determine if low charge was the cause. It is ill advised to try partial charge on the VD compressor systems. Only an evacuate and weight based charge is any surety of correct fill level.
If you find the VD solenoid signal duty cycle is high and low side and high side differ by only a few psi (95 low side, 105 high side) then the compressor is at low displacement and the very likely cause is a stuck VD solenoid. This is a common ailment on all electrically controlled VD compressors and can be serviced with a new solenoid. This requires evacuation of refrigerant and vacuum and charge after the valve is replaced.
Second: Set system to the standard settings as prescribed by all manufacturers. Fan at next to high speed. Recirculated inside air. Windows closed. Engine at 1200 to 1500 RPM. Let it go for 5 minutes to get stabilized and then worry about pressure readings. If it is definitely low don't wait as the time is not going to change pressure or cool the inside of car if it is no doubt low on charge.
For single evaporator (not an XC90) systems the low side should get to mid 20's after it has cooled the interior down to 75F or lower. Once it gets to mid 20's the evaporator will get cold enough that the thermistor signal will have CCM shut down compressor via signal over CAN to ECM on P2 or on P1 and P80 the pressure cycling switch will interrupt signal to shut off compressor until pressure (and thus temp) rise back to higher level (low 40's). If you have not overfilled the system then turning fan down to lowest speed once the car has cooled down some will make the system cycle compressor quickly but not every 10 seconds. Also, with the car still hot inside the low side line back to compressor will not be so cold. don't be too quick to add more charge if it is not close to freezing cold initially. The heat in car is completely evaporating the refrigerant inside and the chilling effect on that line will not be much. After the car is 75F or lower inside that line should be very chilled then.
The low side pressure will get lower with cooler interior temps as will the high side pressure.
If you are working on any P3 or an XC90(P2) with 3.2 or V8 then you have variable displacement compressor and the elevated engine speed for testing and partial charge still applies but the variable compressor will give you fits with pressures once the car cools down. If a VD compressor car has poor A/C performance the first step is to monitor the VD solenoid signal to see that is is 70% or higher duty cycle. If it is not with a hot car then the evap temp probe or other issues exist. If the signal is high and the low side is not chilling with below normal pressures low and high sides then add a bit of refrigerant to see if it drives pressure towards normal to determine if low charge was the cause. It is ill advised to try partial charge on the VD compressor systems. Only an evacuate and weight based charge is any surety of correct fill level.
If you find the VD solenoid signal duty cycle is high and low side and high side differ by only a few psi (95 low side, 105 high side) then the compressor is at low displacement and the very likely cause is a stuck VD solenoid. This is a common ailment on all electrically controlled VD compressors and can be serviced with a new solenoid. This requires evacuation of refrigerant and vacuum and charge after the valve is replaced.
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