OEM 37760-MB9-000 large nut head, twin sensor, thermal fan switch replaces the switch located behind the radiator of all 1975 to 1987 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.