How does a semi truck fan clutch work?
A Fan Clutch engages the fan and makes it turn when the valve opens; it pushes the PFD (Piston Friction Disc) against the friction material and also sends air pressure to overcome a spring. It disengages when the valve is closed, which allows the solenoid to exhaust air and let the spring return.
What activates a fan clutch?
Most fan clutches are filled with a silicone-based oil. The oil is held in an internal reservoir when the fan is disengaged. To engage the fan, internal valves open and allow the fluid to fill the working area of the clutch. This creates friction between the drive plate and the housing, causing the fan to spin.
How can you tell if a fan clutch is bad?
To confirm the diagnosis, start with this simple test: Spin the fan as hard as you can on an engine that has not been started that day. If the fan rotates more than five times, you can bet the clutch is bad. You should feel some resistance and the fan may spin up to three times, depending on the ambient temperature.
How does a fan clutch failure?
Engine overheating at low speed or when stopped is the most-common fan clutch failure symptom. When cruising, the vehicle moving through the air pushes air through the radiator, cooling the engine. Silicone fluid leaking from the fan clutch would cause this problem.
What sensor controls the fan clutch?
Fan speed sensors are used in vehicles for two purposes. Vehicles with a fan clutch use the fan speed sensor to make sure the fan is running. Vehicles with an electric fan use the fan speed sensor to ensure the fan speed coincides with the fan speed that the Powertrain Control Module (PCM) requires.
At what temperature should a fan clutch kick in?
Your radiator fan should kick in at about 200 degrees Fahrenheit. If you notice your vehicle is overheating or at the very least running hotter than it normally does, listen for the fan to see if you can hear it.
How tell if fan clutch is bad?
How does a non thermal fan clutch work?
Non-thermal clutches operate solely based on the shaft speed of the water pump. At low and idling speeds, the clutch allows the fan blade to turn at almost a 1:1 ratio.
What happens to the fan clutch at high speeds?
At high speeds, the silicone fluid within in the clutch will lose its ability to transfer the energy from the shaft to the fan clutch body (and therefore, the fan) and the fan is then allowed to almost free-wheel, removing its load from the engine.
What does a Horton fan clutch do on a truck?
A Horton fan clutch’s prime function is to engage and disengage the engine fan with a clutch controlled by an air-actuated solenoid valve. On modern vehicles the solenoid receives signals to turn on and off from the engine’s ECU. On older trucks, the signals are sent from the temperature sensor.
What makes the fan turn on a truck?
On older trucks, the signals are sent from the temperature sensor. The clutch engages and makes the fan turn when the valve opens, sending air pressure to overcome a spring and push the Piston Friction Disc (PFD) against the friction material.