HVACopediaGoodman · Air handler troubleshooting
Outdoor unit not communicating - ComfortBridge AVPTC/MBVC
What is going on
Communicating system where the outdoor unit does not run or the air handler shows a communication error (EC1). Uses the on-board red communications LED, green receive (Rx) LED and learn button.
Likely causes
- No power or blown fuse at the air handler
- Shorts or open wires in the 1, 2, R, C wiring
- Several wires forced into one connector terminal
- Indoor and outdoor 24 V commons at different ground potential
Check in this order
- Check the green Rx LED off means no power or no network traffic - check breakers and the 3 A fuse, look for low-voltage shorts.
- Rapid flashing green Rx LED is normal network traffic.
- Inspect terminal-block connections; use one wire per terminal and join extra wires with wire nuts.
- Use 18 AWG thermostat wire; keep each run (indoor to outdoor, indoor to thermostat) to 100 ft or less.
- If an outdoor transformer is used, tie the two 24 V commons together with a spare wire; with only two wires, ground the outdoor C to chassis.
- Hold the learn button about 2 seconds to reset the network, then watch the codes on the 7-segment display.
Applies to: ComfortBridge AVPTC**14 (B*) / MBVC air handlers with communicating ASXC/ASZC/DSXC/DSZC/GSXC/GSZC outdoor units
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Source: Goodman ComfortNet ASXC/GSXC/DSXC, ASZC/GSZC/DSZC, AVPTC/MBVC service manual, Communications Troubleshooting Chart p.19; network notes p.44. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.