With only continuous fan enabled the ECM blower starts to rev up, after about 3 seconds it stops with a clunk then it immediately try's to rev up again. The rev up and stop continues to cycle until I disable the fan. The fan RPM never gets above about 75 RPM. The system is a tranquility 22 (TZV 048) which has been running fine for two and a half years. Is it common to have ECM motor failures like this ?? Motor assembly with controller is p/n 14B0037N05. Will I have to replace the assembly or can I get the the ECM controller separately?