Measurement:
NOT CURRENTLY USED
Given a normal flow rate through the boiler the voltage from the flow sensor will switch between 5V and 0V
so fast that it tricks the multimeter into showing 2.5V (or just a slight fluctuation).
Because you are able to see it switching between 0V and 5V
this would indicate a low flow rate through the boiler.
This could be correct and may not be the cause of FD fault
but generally indicates a problem in the system.
Please select appropriate option:
If you are in doubt select option 1 as this is the most common reason.
1. POOR FLOW RATE THROUGH BOILER - SYSTEM RESTRICTED OR BLOCKED
Further investigation will be needed and possible causes will depend on system the appliance is fitted to.
2. FLOW RATE SATISFACTORY - FAULTY FLOW SENSOR
You have already investigated and are confident flow rate through the boiler is ok, sensor is not registering flow rate correctly.
3. LOW FLOW RATE CORRECT - BOILER INCORRECTLY SHOWING FD FAULT CODE
Low flow rate could be correct on an extremely small system or with a pump that will modulate to very low rates.
