Comfortmaker
No Power / Control Circuit Failure
The Comfortmaker system will not start at all; there is no indoor or outdoor operation.
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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
Tripped main breaker, blown low-voltage fuse on the indoor control board, broken thermostat cable, faulty thermostat, open transformer.
How to Fix / Troubleshooting
Safety: Use caution when working around live circuits. Turn off breakers before removing panels.
Steps:
- Check breakers: Verify both air handler and condenser breakers are ON. Reset once if tripped.
- Inspect low-voltage fuse: On Comfortmaker boards, look for a 3–5A automotive-style fuse. Replace if blown, but investigate shorts in the thermostat wiring.
- Test thermostat: Ensure the display is on and set to COOL. Replace batteries if applicable.
- Bypass thermostat (advanced): With power off, temporarily jumper R to Y and G at the air handler to see if the system starts when power is restored. If it does, the thermostat or cable is suspect.
- Check transformer: Measure 24VAC output from the transformer. Replace if no output.
Call a technician: If fuses keep blowing or no 24V is present, professional diagnosis is needed.
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Repair Difficulty
Medium
3/5
Required Part
24V Transformer and Control Board Fuse
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