Hi all,
New here and also new owner of a 2009 Mini S that I picked up for a spare daily driver. My AC went out and I'm looking for the following assistance if its out there. Currently I have the following:
Compressor tests good at the compressor with voltage applied
Relays under hood test good (although there seems to be some question on what relay does what in this car...finding conflicting info)
Low side port reads way high
The fans don't appear to be operating (from my reading this would cause ac not to function and my reading indicates there are 2 fans to look at)
Cabin blower is fine, when I engage the ac ..buttton lights and I can feel / hear the engine react but no cold air
So...before I start diagnosing the electric start to finish, I'm hoping someone has been down this road before and might be able to point me in a direction to look first...ie...are there resistors or sensors in this circuit that would kill the ac if not functional? I appreciate the help in advance. Have a great day and Thanks!

 

The fans need to be working or the condenser will not work as intended. It is better to have the system working otherwise you will be running in circles. Get the electric sorted out and post the low/high side pressures along with ambient temp.

 

Thank you. I appreciate the help.

 

If you connect the gauge set when the engine is cold the static pressure should be around 4psi higher than the ambient temp. The low and high sides should be the same since they should have equalized.

 

Air conditioning systems are a sub-set all their own, and typically require specialized training and tools to diagnose and repair.


For example. Even though you have tested the compressor clutch for proper engagement (energizing it with 12 VDC), you have no idea if the compressor is functioning properly in relation to pressure and flow of the refrigerant. Gauges can help you out there, but you have to know how to read them. You also have no idea if the expansion valve is working properly. Again, gauges can help you determine this. You say the fans aren't working, but are they getting voltage? Depending on the age of the car, the fan motors may be shot. The fan motors are your "break point" (where the voltage stops and the mechanical (turning the fan) starts.



You said the low side reads "way high" What is "way high" in PSI? What was the ambient temp? Do you have an external fan blowing air through the condenser?


Yes, the typical AC system has a low-side pressure switch, and a high side pressure switch. Some systems have other sensors, relays, and switches. I'd have to look in the manual as I have not experienced any AC issues with our MINI yet (knock on wood), so I haven't read up on it yet.


So what's next? Connect both high pressure and low-pressure gauges; get an external fan and set it so it's blowing air through the condenser. Start the car, turn on the AC, and set engine RPM to 2000. Report what your low-side and high-side pressures and your ambient air temp. humidity is also a factor. Let us know your findings. This will be difficult over the internet, because we need to see the gauges as the system cycles. If the condenser fan is not turning; pull the connector (begin careful of the exhaust manifold), and check for 12VDC to the motor.

 

Kevin, to give you a comparison, here's what my MINI pressure readings look like at 80 Deg F, 2000 RPM, w/ a fan blowing air through the condenser. My car has 124K miles on it. Compressor is the original. Air is cold, but as you can see from the gauges, and the pressure chart, I'm low on refrigerant.



High Side

Low Side

Pressure Chart