Boyertown Furnace RSM 500 Installation, Operation And Maintenance Manual page 31

Nidec ECM Troubleshooting
General Troubleshooting
1. Check unit for power.
2. Disconnect or turn off power to the furnace, air handler, or system being serviced and wait 2
minutes. This allows the capacitors in the control unit to fully discharge.
3. Check control unit connectors. Inspect for shorts, detached wiring and or loose connections.
4. Check power cord and communication cable connections. Make sure both are securely connected
to control unit connectors.
5. Check blower motor to ensure that spins freely manually without effort. If binding occurs check
that blower wheel is not binding in the housing.
Electrical Checkout Motor
1. Disconnect or turn off power to the furnace, air handler, or system being serviced and wait 2
minutes. This allows the capacitors in the control unit to fully discharge.
2. The HVAC system must be wired for 120 VAC power. Verify a jumper wire is installed between
positions 1 and 2 of the power cord connector.
3. Disconnect power cord from connector on the control unit. Inspect power cord for bent, damaged
or recessed wires and terminals.
4. Restore or turn on power to the furnace.
Electrical Checkout 16 x 4 Wire Box
1. With power applied to the furnace both the "RX" and "TX" lights should be flashing during
normal operation.
2. Disconnect or turn off power to the furnace, air handler, or system being serviced and wait 2
minutes. This allows the capacitors in the control unit to fully discharge.
3. Disconnect 4-wire communication cable from connector on control unit. Inspect cable for bent,
damaged or recessed wires and terminals
4. Restore or turn on power to the furnace.
5. Check the voltage between positions 1 and 4 of the communication cable connector. If the
measured voltage between positions 1 and 4 is NOT 30-35 VDC replace the 16 X 4 wire box. If
the measured voltage between positions 1 and 4 is 30-35 VDC, go to control unit verification.
4 Pin Communication Cable
31