What you are hearing is the compressor coming off of the mounts and slamming back down on them. Or the compressor jumping, swinging, or in general not being properly restrained by the rubber mounts.
This can be easily checked and repaired. Just watch the compressor as it stops (unplug it when it is running).
If the compressor is restrained and there is still a loud clunk then something inside the compressor is coming loose and the whole unit must be replaced. This is not very likely as this would cause the compressor to fail in short time.
If this answer satisfies your question please click on the accept button. If it does not, please tell me so. You are not expected to accept any answer that you are not happy with. I do expect you to let me know if you are not satisfied, and what I can do to put a smile on your face.
Thank you for using Just Answer. Please tell someone about us.Best regards; The Home SmithyAfter you have accepted it is important that you leave positive feedback.