Control units control. They use inputs to make a decision. Typically overloaded circuits occur on the outputs. Outputs are these things: auxilary water pump, aux fan control, switchover valves, and clutch control. In the first three if the device is shorted the controller either protects itself (as the engine controllers will do) or will burn out. In the case of the clutch control; this is a ground circuit (to a separate relay)so a short would be (and I've seen it numerous times) where someone thinks they can hot wire the compressor control with battery voltage. The ground circuit in the controller is designed to pull down a transistor not a battery.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician