Pentair Max-E-Therm ERR AFS Error
The ERR AFS error on a Pentair Max-E-Therm indicates the air flow switch is open. This means the blower is not running or airflow through it is restricted.
If adequate airflow is established within 60 seconds, the heater will resume normal operation. Otherwise, press HEATER OFF to clear.
What Causes ERR AFS?
The air flow switch verifies that the blower is moving enough air for proper combustion and venting.
Common Causes
- Blower not running: Motor failure or electrical issue
- Blocked exhaust: Debris in vent termination
- Restricted intake: Blocked air intake
- Condensate blockage: Water blocking airflow
- Failed air flow switch: Switch stuck open
- Loose connections: Wiring to blower or switch
Troubleshooting Steps
Step 1: Check Blower Operation
- Listen for blower motor running when heater calls for heat
- Blower should start before ignition
- If no blower sound, check motor and connections
Step 2: Inspect Exhaust Vent
- Go to vent termination outside
- Remove any debris (leaves, bird nests, etc.)
- Ensure vent is not blocked by snow or ice
- Check that termination cap is intact
Step 3: Check Air Intake
- Verify intake vents are clear
- Remove any debris around heater
- Ensure nothing is blocking combustion air
Step 4: Check for Condensate Issues
- Inspect condensate drain for blockage
- Verify condensate is draining properly
- Clear any blockages in drain line
Step 5: Test Air Flow Switch
- Turn off power to heater
- Locate air flow switch
- With blower running, switch should be closed
- If switch doesn't close with good airflow, replace it
Blower Motor Check
If blower isn't running:
- Check electrical connections to blower
- Verify control board is sending signal
- Test blower capacitor if applicable
- Test blower motor windings
When to Call for Service
- Blower motor needs replacement
- Internal vent inspection needed
- Air flow switch needs replacement
- Control board diagnosis required