Thermo fan switch that replaces Honda OEM 37760-MT2-003 for GL1500, Valkyrie and several Honda models.
Your thermostat fan switch (or thermostatic switch according to Honda) that is threaded into the rear of your radiator may be dead or shorted out.
DO NOT TEST A NEW THERMO FAN SWITCH IN A HOT WATER OR OIL BATH PRIOR TO INSTALLATION OR YOU MAY COMPLETELY DISABLE THE COMPONENTS OF THE SWITCH. Years ago, a customer claimed our thermo fan switch was bad and demanded a replacement. Afterwards we learned he tested it "per the Honda Service Manual" and "heated/cooled it in hot oil on the stove" hoping to turn the fan off at 197 F. This customer had confused the THERMOSTAT with the THERMOSTATIC SWITCH in Honda's manual.
Fan operation failure is due to only two things:
1) faulty thermostatic or thermo fan switch 2) faulty fan motor.
There is a simple procedure to determine which one is faulty. Simply remove the fan motor and hook it up to a 12 V battery to energize the motor. If the motor operates freely and steady, your thermo fan switch is the culprit.