Fitted a 1000 watt dimmer to control a customers ceiling lights, 550 watts in total of 50 watt 12v downlights. When the dimmer is turned down the microwave buzzes. The lighting circuit and kitchen ring have all been tested, all fine, excellent readings for Zs, ring continuity, insulation etc... The dimmer hardly buzzes at all..!!! I took the microwave and plugged it in to the old part of the house, which is fed from a different fuseboard in a different part of the house, and it still did it. This has been happening for about a month now, and today the customer phoned to say her microwave has packed up. Its a few years old, so is this just a coincidence, or has the dimmer somehow caused the microwave to blow...? Also, on the same point, the house is a TT system, and when i check for PFC, i get a reading of 4amps every time. Not had anything like that before... why the hell is it only 4 amps...?