Brand: bryant
Category: Furnace
Manual Type:
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Manual for RESIDENTIAL FAN COIL UNITS - Troubleshooting and error codes + PDF Download
Uploaded: April 7, 2025, 8:11 p.m.
Manual Publish Date: 1999-06-01
Warranty Summary
No warranty information is present in this service manual.
Continuous Fan Mode: Thermostat closes circuit R to G, signal sent to ICM2.
Cooling Mode - Single/2-Speed High: Thermostat closes R to Y/Y2 and R to O (heat pump), R to Y1 for 2-speed high, Y/Y2 signal to ICM2.
Cooling Mode - Two-Speed Low: Thermostat closes R to Y1 and R to O (heat pump), Y1 signal to ICM2.
Electric Heat Heating Mode: Thermostat closes R to W2, W3, or E. Jumpers JW1 & JW2 for staging.
Heat Pump Heating Mode - Single/2-Speed High: Thermostat closes R to Y/Y2 for single speed, R to Y1 for 2-speed high, Y/Y2 signal to ICM2.
Heat Pump Heating Mode - Two-Speed Low: Thermostat closes R to Y1, Y1 signal to ICM2.
Heat Pump Heating With Auxiliary Electric Heat: Thermostat closes R to Y/Y2/Y1 with R to W2/W3/E (R to O for defrost).
Troubleshooting and error codes
| PROBLEM | CAUSE |
|---|---|
| If Fan Will Not Turn On from Thermostat (No High Voltage to Transformer) | Check plug/receptacle connection, sequencer/relay & plug wiring, field power leads L1 and L2. |
| If Fan Will Not Turn On from Thermostat (PCB Has High Voltage) | Check low-voltage transformer leads, output voltage, low-voltage fuse, primary side transformer connections. |
| If Electric Heat Stages Will Not Turn On But Fan Will Turn On (No High Voltage to Transformer) | Check plug connection between heaters and board, sequencer/relay & plug wiring, incoming high-voltage power leads. |
| If Electric Heat Stages Will Not Turn On But Fan Will Turn On (Transformer Has High Voltage) | Check low-voltage transformer leads, output voltage. |
| If Traces Are Overheated on Back of PCB | Ensure PCB is wired correctly before applying power. |
| If Transformer Fuse Keeps Blowing | Check wiring of sequencers/relays, VA draw on transformer. |
| If Fan Runs Continuously | Check blue and black fan leads, fan relay. |
Troubleshooting and error codes
| PROBLEM | CAUSE |
|---|---|
| If Fan Will Not Turn On from Thermostat (No High Voltage to Transformer) | Check plug/receptacle connection, sequencer/relay & plug wiring, field power leads L1 and L2. |
| If Fan Will Not Turn On from Thermostat (PCB Has High Voltage) | Check low-voltage transformer leads, output voltage, low-voltage fuse, primary side transformer connections. |
| If Electric Heat Stages Will Not Turn On But Fan Will Turn On (No High Voltage to Transformer) | Check plug connection between heaters and board, sequencer/relay & plug wiring, incoming high-voltage power leads. |
| If Electric Heat Stages Will Not Turn On But Fan Will Turn On (Transformer Has High Voltage) | Check low-voltage transformer leads, output voltage. |
| If Traces Are Overheated on Back of PCB | Ensure PCB is wired correctly before applying power. |
| If Transformer Fuse Keeps Blowing | Check wiring of sequencers/relays, VA draw on transformer. |
| If Fan Runs Continuously | Check blue and black fan leads, fan relay. |