What Does Trane RTU Error Code 45 Mean?
On many Trane rooftop units, Error Code 45 indicates a supply fan proving switch fault or airflow verification failure. The controller is not receiving confirmation that the supply fan is operating as expected.
When this fault occurs, the unit may:
- Prevent compressor operation
- Disable heating or cooling stages
- Enter lockout mode
Common Causes of Error Code 45
Typical causes include:
- Failed airflow proving switch
- Broken or loose tubing to pressure switch
- Dirty filters
- Failed supply fan motor
- Blower belt failure (belt-driven units)
- Faulty fan contactor
- Control board input issue
Airflow restrictions are among the most common causes.
How to Troubleshoot
1. Verify Fan Operation
Confirm the supply fan motor is running when commanded.
Check:
- Motor amperage
- Belt condition
- Shaft rotation
2. Inspect Airflow Proving Switch
Check:
- Tubing for cracks or blockage
- Proper pressure differential
- Electrical continuity
Replace the switch if it does not close under proper airflow.
3. Inspect Filters and Coil
Restricted airflow can prevent the proving switch from closing.
Replace dirty filters and clean coils as needed.
When to Replace Components
Replace the airflow switch if:
- It fails continuity under proper airflow
- Tubing is intact but no signal is present
Only suspect control board failure after verifying mechanical components.
FAQ
Will the unit cool with this fault active?
Usually no. The unit prevents operation without verified airflow.
Is this a serious fault?
It protects the equipment from operating without airflow.