Pahlen
Stuck Fan Relay or Control Logic Fault
Heater fan (combustion blower) runs continuously even when there is no call for heat.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Stuck relay on Pahlen control board, Shorted fan wiring, Incorrect external control signal holding heater in purge mode, Faulty air pressure switch feedback
How to Fix / Troubleshooting
Safety first: Turn off power before accessing the control compartment.
Step-by-step checks:
- Verify call for heat: Ensure that the thermostat or pool automation is not continuously calling for heat. Lower the setpoint or disconnect the external control signal to test.
- Inspect fan wiring: Check the blower motor wiring for shorts or miswiring that could be feeding constant power.
- Observe control board: With the cover removed (and using caution around live parts), observe whether the fan relay on the Pahlen board is stuck closed. A technician can test this with a meter.
- Check pressure switch: A stuck-closed air pressure switch can confuse the controller. Test it for proper operation as the fan starts and stops.
When to stop: If the fan relay is welded closed or the board logic is faulty, the control board must be replaced by a professional.
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Repair Difficulty
Hard
4/5
Required Part
Pahlen control board (fan relay circuit)
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