Protherm
No Power / Main Fuse or Power Supply Failure
Furnace does not start at all, no display, no lights
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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
Blown internal fuse on Protherm PCB, Tripped circuit breaker, Loose mains connector, Failed internal power supply on PCB
How to Fix / Troubleshooting
Safety first: Turn off the main breaker before opening the furnace. Only qualified persons should work on mains voltage.
- Step 1 – Check external power: Verify that the wall switch is on and the circuit breaker or fuse feeding the furnace has not tripped. Reset if necessary.
- Step 2 – Inspect power cord and switch: Ensure the furnace's main power switch is on and the cord or fixed wiring is intact.
- Step 3 – Internal fuse: With power off, remove the front cover and locate the PCB fuse. If blown, replace only with the same rating. If it blows again, a deeper fault exists.
- Step 4 – PCB power supply: If fuses and external power are good but there is still no display, the PCB's power supply is likely defective and the board must be replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Main Control PCB
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