2003 TrailBlazer Fan Clutch Problems

The fan clutch in your 2003 Chevy TrailBlazer is mounted between the fan and the fan belt pulley on the water pump. The fan clutch is what controls the turning of the fan which is activated by a thermostat. Problems with the fan clutch can cause your engine to overheat, run on the hot side or not heat up properly.

Electrical Problems

  • The fan clutch on a 2003 TrailBlazer is electronically controlled. If the thermostatic switch that controls it goes bad, the clutch can either lock up, causing it to spin at engine RPM, which keeps the engine from heating up properly, or it can free spin, causing the engine to run overly cold. If the element inside the clutch goes bad, these same problems can occur. The electric switch is also engaged when the air conditioner is turned on, which causes the fan blade to spin almost as fast as the engine itself. If this switch goes out, the fan won't spin fast enough, causing the engine to possibly overheat.

Internal Valve Problems

  • The electronic clutch on the 2003 TrailBlazer is controlled by a valve and a spring. As the engine heats up, a spring expands, causing a valve to open and allowing a viscous silicone fluid to flow through the valve. The fluid engages the clutch and speeds up the fan. If this valve leaks, either internally or externally, the fan can either spin too fast or too slow, causing the engine to either take too long to heat up or to heat up too quickly and possibly overheat.

Internal Clutch Spring Problems

  • If the thermostatic spring in the fan clutch breaks, the valve won't be able to open or close. If the valve was open when the spring broke, the fan will run at almost engine speed, not allowing the engine to heat up properly. If the spring broke when the valve was closed, the fan won't be able to spin fast enough when the engine is at operating temperature, which can cause the engine to overheat.


  • The type of fan clutch on the 2003 TrailBlazer is quite different from other fan clutches since it's electronically-controlled and it threads onto the snout of the water pump, instead of being bolted to it. In order to change this type of clutch, you will need a 36 mm wrench to turn the center shaft. You will also need a ½-inch socket to remove the plastic fan blades from the clutch.