# x5 e70 x6 e71 ac pressure switch replacement question



## chenkel (21 d ago)

Hhello team,
i want to replace the ac pressure switch on my 2013 X6 35xi E71.
I know the ac system is basically the same as the X5 E70.
What i dont know is if the pressure switch on e70/e71 cars can be replaced without losing all the freon charge.
I would think the port it threads onto has a schrader valve that opens after the pressure switch threads in so far and closes as the switch is unscrewed for removal.
Can any one confirm this for me.
Most vehicles are like this now but i want to make sure before i change my pressure switch out and it vents all my freon.
Reason: my ac compressor magnetic clutch is not powering up when requested and engagimg the clutch. One of three likely cluprits is the switch and i have a good spare and want to just eliminate that issue from the start.
it is freezing outside and it will be a quick and easy start to eliminating posibilities, as long as it doesnt dump the freon charge.
Thank you in advance.
christopher


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## Doug Huffman (Apr 25, 2015)

No, you cannot replace the Refrigerant Pressure Sensor B97 (not switch), and it is not likely the source of your problem.

A/C Compressor Control
The IHKA is the master for controlling the A/C compressor. Pressing the AC button on the air conditioning system operating unit switches the air conditioning system to the ready state.The IHKA transmits a speed increase request to the DME (ECM).
Depending on the temperature and the nominal-value setting, the IHKA sends a cooling power request to the DME (ECM) If the DME (ECM) is ready and in a position to provide a torque of > 20 Nm, the DME (ECM) issues a release for a load connection of up to 30 Nm. This release is also monitored by the junction box. The IHKA issues a command to the junction box to couple the connection. The junction box returns the coupling status to the DME (ECM)
The compressor output is controlled by the IHKA control unit by means of an infinitely variable control valve. The IHKA control command is converted into infinitely variable pro- portional powering of the control valve in the junction box.
The control is designed as "sliding evaporator control".
The evaporator temperature is controlled to a value of between 2°C and 8°C depending on the cooling power request. The temperature sensor signal in the evaporator is used as a feedback signal to the IHKA control unit. The coolant request is limited by the potential evaporating power of the evaporator.
The evaporator is prevented from icing up by controlling the compressor output (appro- priate reduction).
In order to reduce CO2 emission, avoid unstable conditions when the engine is idling and for full load acceleration the DME can activate a compressor shut-off via the junction box. If appropriate parameters are present, the solenoid coupling of the compressor is opened.

Pressure Sensor via Junction Box
The refrigerant pressure input signal is a direct junction box input signal and is relayed to the IHKA via the K-CAN. The IHKA requests actuation of the auxiliary blower by the DME (ECM) depending on the refrigerant pressure.
The IHKA determines the relevant A/C compressor load torque on the basis of the input signals from the pressure sensor and the compressor speed. The DME (ECM) control units are notified of the load torques by the IHKA and used by the DME (ECM) as input variables for actuating the electric fan.
Refrigerant Circuit Pressure Sensor


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## chenkel (21 d ago)

So…about I got from that hi level factory engineering citation was “ no, if you remove the pressure sensor it will evacuate all your freon.” Thank you for that..
I comprehended most if the info about how the signals and modules monitoring and controling the system.
Thanks. 
Not sure what help it is. I understand and troubleshoot basic ac system issues.
I know this one is more complex.
Is it still not true that if the pressure sensor is not operating properly, the ac “brains” may see no or too low system pressure and determine it is not ok to engauge the compressor / clutch? i mean I am sure it monitors the pressure and provides an analog or digital signal indication pressure. This would give the system a go or no go inout. The system is for sure looking for iit to be at least 35-45 psi on the low side right. I am sure it also monitors the evap temp, outside air temp, and even the BMW AUS sensor for ac operation. Wouldn’t some or all these sensors with a false or improbable signal tell the ac system it is not ok to engage the compressor?

I was mainly posting to find out if the freon would vent.
My goal is to see that the sensors are all working correctly and the basicas are good before I drive this car an hour to the nearest dealer for them to tell me its a 50 to $100 sensor and here is your $1000 bill for our service.
Everything else on the car is fine and the car drives great.
It is 2 degrees F outside now. I thought I would start gathering some info for troubleshooting the sensors.
However, here is what I am seeing if you are any good at hi level diagnosis.

i have a bi directional scanner / programmer. it is telling me their is an issue with the clutch not engaging. 
I can connect with inpa and a laptop but havent yet. project car is in the heated garage and again it is single digits outside.
Here is what a quick fault code scan gives .

00A72F magnetic clutch air compressor
00E704 K-CAN bus erorr
00E2C4 Bus low line fault

all three come up in ac system issues.

Thank you


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