I hear a click every 7 to 12 seconds as the AC compressor in my 03 E350 cycles on/off while driving, whereas at idle the compressor runs continually (at least when the ambient is 80 F+). Is it normal to cycle so frequently while moving? Had a new compressor in June 04 under warranty. However, the 7 to 12 second cycling has been there since we got the vehicle in May 03. Seems to cycle off when low pressure reached on low pressure side and kick in again as pressure reaches 45 psi or so. Would such frequent cycling be hard on the compressor and clutch etc?

 

At 80 degrees, the system isn't working too hard so if it's moving, the heat exchange will be quick. Sounds like it's working like it should.

 

I have researched those electromagnetic clutches very recently and found that they are designed to handle in excess of 100 cycles per minute with no trouble at all. Your pump sounds like it is cycling at 8.5 - 5 cycles per minute which is nowhere near the pumps upper capability.