System Overview
The engine cooling fan system is composed of one cooling fan, 2-relays, the enginecontrol module (ECM), and the associated wiring. The cooling fan assembly includes1-resistor mounted in the cooling fan shroud. The cooling fan resistor may be a standalone component, or a part of the cooling fan motor and harness assembly. This combinationof components enables the ECM to operate the cooling fan at 2-speeds usingtwo fan control circuits. The ECM will operate the cooling fan at either Low or Highspeed based on the cooling requirements.
Low Speed Operation
The ECM applies ground at the FAN-1 control circuit for the coil side of the low speedcooling fan relay. The energized low speed relay switch closes to supply B+ throughthe cooling fan resistor, to the engine cooling fan motor. The result is cooling fanoperation at a reduced speed.
High Speed Operation
The ECM applies ground at the FAN-2 control circuit for the coil side of the coolingfan high speed relay. The energized high speed relay switch closes to supply B+ directlyto the engine cooling fan motor, by-passing the cooling fan resistor. The result iscooling fan operation at full speed.
Electrical System Overload
The vehicle has fuses and circuit
breakers to protect against an
electrical system overload.
When the electrical load current is
too heavy, the circuit breaker opens
and closes, protecting the circuit
until the current load returns to
normal or the problem is fixed. This
greatly reduces th ...