Temperature sensor
Common error-code part. Confirm resistance and connector style.
Heatcraft ZER/ZR Series Alarms — Quick Reference
Heatcraft ZER and ZR unit coolers use electronic defrost and temperature control packages in walk-ins, prep coolers, and refrigerated storage rooms. Alarm messages usually come from the controller mounted near the evaporator or in the condensing unit panel.
| Alarm | Meaning | Quick Fix |
|---|---|---|
| P1 | Room sensor fault | Check room probe and wiring |
| P2 | Coil sensor fault | Check evaporator probe and placement |
| HA | High room temperature alarm | Check refrigeration performance and door usage |
| LA | Low room temperature alarm | Check control setpoint and sensor calibration |
| dF | Defrost active / stuck in defrost | Check defrost heater, timer, and termination sensor |
| Fan Alarm | Evaporator fan issue | Check fan motor and blade obstruction |
| Door Alarm | Door open input active | Check door switch and door seal |
Most Common Alarms
P1 — Room Sensor Fault
The controller lost the room temperature sensor. Check the sensor plug first. Then inspect the probe wire where it passes through the case or ceiling. Probe cables often get pinched. Replace the sensor if resistance is open or shorted.
P2 — Coil Sensor Fault
The evaporator coil probe controls defrost termination. If it fails, the unit may stay in defrost too long or fail to defrost. Make sure the probe is firmly attached to the coil and insulated from ambient air.
HA — High Temperature Alarm
A high box temperature alarm usually points to airflow or refrigeration problems. Check for iced coil, failed fan motor, dirty condenser, or a door left open. If the room was recently loaded with warm product, the alarm may clear after pull-down.
Defrost Troubleshooting
- Force a defrost cycle from the controller.
- Confirm the defrost heaters energize.
- Watch the coil sensor temperature rise.
- Verify the unit exits defrost on temperature or time.
- Confirm fans restart after drip delay.
Parts Often Needed
| Part | Notes |
|---|---|
| Room temperature probe | Replace on P1 alarms |
| Coil defrost probe | Replace on P2 alarms |
| Defrost heater | Check continuity if ice builds heavily |
| Evaporator fan motor | Replace on fan alarms or no airflow |
Related Resources
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- Beverage-Air Refrigerator Error Code E2 — Evaporator Sensor …
Need Replacement Parts?
Before ordering, match the machine-control part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
Jump to Fix
- P1 → Check probe connection → Measure resistance → Replace sensor
- P2 → Check coil probe location → Measure resistance → Replace sensor
- HA → Check fans → Check coil icing → Check condensing unit
When to Call a Pro
If the unit cooler keeps alarming after probe replacement, the problem may be in the condensing unit, TXV, or defrost circuit. A refrigeration technician should check pressures and superheat.