Fuel economy

[Urnie-Medie]

Hi David
Probably a dumb question - how do I determine if it is running all the time and how could I correct it?

[davidbrady]

Urnie,

At fast idle, disconnect the packard connectors at the Fan Drive Control Assembly (FDCA). This is the contraption that converts the Detroit Diesel pulse width modulation electrical signal into a proportional hydraulic pilot signal. The hydraulic pilot signal connects to the flow control valve at the fan motor and tells the fan to speed up or slow down. If you disconnect the packard connector signals from the FDCA, the fan should default to high speed. High speed may only be noticeable at fast idle or above. If the fan speed doesn't change then it's probably always on high speed. High speed is usually unmistakable because of the roar the fan makes, but if you're not familiar with it you may not be able to tell by sound.