ATL
Ambient Temperature Limited
This code typically points to
- Outdoor ambient outside allowable range for the current operating mode
- Thermostat/reversing-valve programming issue
- Power present on B wire outside during a cooling call
Next checks to confirm
- Confirm ambient reading on board display against actual outdoor ambient after 5 minutes idle
- If code is latched, remove Y wire and cycle disconnect to view outdoor temperature on display
- Replace T4 sensor if displayed ambient is not within 10 degrees F of actual
- Confirm ambient is within Bosch published operating thresholds
- Verify thermostat/reversing-valve logic for the current mode
Escalation
Operating limitation — no normal operation until ambient or control condition is corrected
Reset behavior
Clears when ambient/control condition is corrected and system is power-cycled or resumes normal operating conditions.
Service Soon
Schedule repair