F4
ATAG
Diverter Valve Position Fault
Furnace shows F4 and stops, often when switching between heating and hot water
Advertisements
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.
Advertisements
Possible Causes
Stuck diverter valve, Faulty diverter valve motor/actuator, Debris in hydraulic block preventing valve movement
How to Fix / Troubleshooting
Safety first: Isolate power and close the cold water and heating isolation valves before working on the hydraulic block.
- Locate the diverter valve assembly on the hydraulic block.
- Listen for the actuator motor when switching between heating and hot water demand; absence of sound may indicate motor failure.
- Check the electrical connector to the diverter motor and reseat it.
- Gently tap the diverter body with a non-metallic tool to free a sticking valve (temporary measure only).
- If the valve remains stuck or F4 persists, the diverter valve cartridge or motor should be replaced by a technician, followed by system refilling and bleeding.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
ATAG diverter valve assembly
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements