The Clyde tester monitors two of the signals that are sent between the load sensor and the temperature controller (ATC). You should test to make sure power is getting to both units. For the load sensor, verify that there's 120 volts AC between the purple wire and the white wire. For the ATC, 120 volts between its white-red and white wires. Note, though, that the load sensor provides the 120V on the white-red, so if the ATC is not getting it, it could be the load sensor's fault. And, while you're measuring, make sure there's 120V on the load sensor between the pink wire and the white one. This is a key line that provides the power for both wash and rinse water flows. All of these measurements are best made with the timer switch at the beginning of a wash cycle and turned on. Disclaimer: You are working with a live electrical device. Electricity does not have to rare back to hit you -- it's already rared back. Do not attempt these measurements unless you are fully aware of what you are doing, the proper precautions to take, and how to use the measuring equipment. (Sorry, I had to do that.) [edit: I did some testing with the Clyde port and found that, while both lines are 'hot' during parts of the cycle and 'not' during other parts, no diagnostic value was immediately obvious. I intend to pursue this issue and will post more if I find out something.]