How can I check the viscous fan coupling or the fluid coupling as called in the FSM is functioning properly. From what I understand its only method of failing is seizing, is this correct? The reason I'm asking is because the place that's rebuilding my air con compressor has told my garage that the viscous coupling failing could cause the aircon to fail. They way I see it is that if the VC fails it will over cool the condenser making it more efficient, so I cant see how it will affect the reliability of the compressor. Anyway need to check if the fan VC is working properly.