I used your troubling shooting guide and bought a defrost heating element. I checked it out with my volt meter and sure enough it was broke. I had also bought a thermistor but after about a week of no noise I sent it back to you guys. Thank you very much for your return policy. Two weeks later the Whirlpool started making the noise again and I order a thermistor from you again and installed it. So far so good. The job did not take long and the longest part was defrosting the ice to replace the parts.