You should get a low resistance between pins 9 and 11. So yes either the sensor is open or you have a broken wire somewhere.

Now since we are finding car based differences, you have to make sure that your compressor has a speed sensor and that the wires of the sensor arrive at the pins 9 and 11. To double check, verify connectivity between sensor connections at the compressor and pins 9 and 11.

This finding fits very well with your symptoms. And if you do find that the compressor speed sensor is broken, I am not sure what you can do about it. You have to call the dealer and see if they can just replace the sensor for you, it is a serviceable part but may be so old that it is not available anymore. Otherwise, will need a new compressor.

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Saumil S. Patel