Okay, since the clutch IS trying to kick in, it very well could be related to the rotational switch. That does not mean that it is the rotational switch or its associated circuit.

The purpose of the rotational switch is to detect a locked up compressor and prevent it from strewing bits all through the system(I think.) A slipping belt can cause what you are seeing. Is the belt tensioned properly, in good shape and not oily?

Good luck,