Danfoss · VLT HVAC Drive FC 102
The control card voltage from terminal 50 has dropped below 10 V. This is typically caused by an overloaded 10 V supply (exceeding 15 mA or below 590 Ω minimum resistance) or a short circuit in a connected potentiometer or its wiring. If left unresolved, this can lead to unstable control card operation or system shutdown.
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Measure the voltage between terminal 50 and terminal 55 on the control board; it must be greater than 10.0 VDC.
Disconnect all external devices from terminal 50; if voltage returns to 10 V, incrementally reconnect devices, measuring current draw with a multimeter to identify the overloading device.
Measure the resistance (in Ohms) of each connected device between its supply input and common; identify if any device resistance is below 590 Ω.
Visually inspect the control card and terminal 50 for signs of physical damage, burnt components, or short circuits.