Thermistor
Common temperature-sensing fault part. Confirm resistance range and connector.
Honeywell TrueZONE Error Codes — Quick Reference
Honeywell TrueZONE zone control panels (HZ311, HZ322, HZ432) display fault codes on a built-in LCD or via LED flash sequences. The panel manages multiple HVAC zones by controlling dampers and communicating with zone thermostats. Faults typically appear when a zone damper fails, a thermostat loses communication, or equipment wiring is incorrect.
| Code / Display | Meaning | Quick Fix |
|---|---|---|
| ZONE FAULT | Zone thermostat communication lost | Check thermostat wiring; replace thermostat |
| DAMPER FAULT | Damper motor not responding | Check damper motor wiring; test motor manually |
| BYPASS FAULT | Bypass damper failed to respond | Inspect bypass damper actuator |
| LOW VOLTAGE | 24VAC supply below threshold | Check transformer; verify 40VA minimum |
| COMM ERROR | Internal communication failure | Power-cycle panel; check board connections |
| ERR 1 | Zone 1 sensor/thermostat fault | Verify zone 1 thermostat wiring |
| ERR 2 | Zone 2 sensor/thermostat fault | Verify zone 2 thermostat wiring |
| ERR 3 | Zone 3 sensor/thermostat fault | Verify zone 3 thermostat wiring |
| ERR 4 | Zone 4 sensor/thermostat fault | Verify zone 4 thermostat wiring |
| EQUIP FAULT | Equipment output fault detected | Check output wiring to furnace/air handler |
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Most Common Faults
ZONE FAULT — Thermostat Communication Lost
The TrueZONE panel lost contact with one or more zone thermostats. This is the most common fault. Check the low-voltage wiring between the thermostat and panel — specifically the C (common) wire. On battery-powered thermostats, replace the batteries. If the fault is specific to one zone, swap that thermostat temporarily to rule out a wiring issue vs. a failed thermostat.
DAMPER FAULT — Zone Damper Not Responding
The damper actuator on a zone did not move to the commanded position within the timeout window. Causes include a failed damper motor, disconnected actuator wires, a mechanically stuck damper blade, or a failed 24VAC supply to that damper. Access the damper in the duct and manually verify the blade moves freely. Most TrueZONE-compatible dampers use a 24VAC spring-return actuator — apply 24VAC directly to the actuator terminals to test it.
LOW VOLTAGE — Transformer Undersized or Failing
TrueZONE panels require a minimum 40VA transformer (some multi-zone configurations need 75VA). If the transformer is undersized or failing, voltage can sag when multiple dampers activate simultaneously. Measure 24VAC at the panel terminals under load — it should remain above 20VAC. Replace the transformer if voltage drops below this.
BYPASS FAULT — Bypass Damper Issue
The bypass (pressure relief) damper is a critical component in zoning systems. If only one zone calls for heating or cooling, excess air pressure must be relieved. A bypass fault means the bypass damper actuator is not responding. This damper is often located in a main trunk near the air handler. Verify the bypass damper wiring and actuator operation.
COMM ERROR — Internal Panel Fault
A general communication error inside the TrueZONE panel. Power-cycle the panel by removing 24VAC for 30 seconds. If the fault persists after reboot, inspect the ribbon cables and board connectors inside the panel enclosure. A persistent COMM ERROR with no wiring explanation usually indicates a failed control board.
TrueZONE Model Notes
- HZ311 — 3-zone panel, supports up to 3 dampers and 3 thermostats
- HZ322 — 3-zone panel with remote sensors and enhanced bypass control
- HZ432 — 4-zone panel, requires 75VA transformer for full load
- All models use the same 24VAC wiring convention; R, C, and G/Y/W outputs per zone
When to Call a Pro
If a damper fault persists after wiring checks, the ducts may need to be physically accessed to inspect the damper blade and actuator. Call an HVAC technician if you are not comfortable working in ductwork or if the transformer sizing needs to be recalculated for your system.