I replaced the defrost timer because it was not working. If I advanced it manually to activate a defrost cycle, it would run long enough to complete the defrost cycle and then the timer motor would stop. New defrost timer does the same thing. It appears that the neutral side of the timer motor (red wire) does not have a complete circuit to neutral. 110v side is good and switches from fan motor to defrost heater when advanced manually. Does this circuit go throught he defrost thermostat? I bypassed it to test and the condition did not change. What else might be in that circuit?