Baxi Solo 3 PF has intermittent fault in that it starts and runs for a short period but will shut down and then immediatly start up again.
When running the "boiler on" "fan on" "pilot on" "burner on" indicators show.
When it shuts down the "boiler on" and "fan on" lights stay on. It sits like this for a few seconds and then the "pilot" and "burner" lights come on and the boiler runs again
Any help or indication of the problem greatly appreciated.
In message , lightning writes
Hmm, interesting one this
If the pilot and main light are both going out, it would indicate that the pcb thinks the air pressure switch has fallen back.
Possible causes
bad joints on the pcb bad contacts on the common to normally open contacts on the air pressure switch the wires that go into the fan windings are held in with pretty crude blades - potential for poor contact there
How often does this happen?
Geoff,
Thanks for your advice.
PCB changed so I think that should eliminate any faults within the board.
When the fault occurs the fan on light stays on and can hear the fan running so I guess no fault with the supply to the fan.
I had assumed the "fan on" light was activated through the pressure switch and with the light on assumed (possibly incorrectly) that the pressure switch was working OK.
The period between the fault showing varies. Sometimes it will show every 4 or
5 minutes other times boiler will run about 20 minutes and then the fault will show 2 or three times in quick succession. But timing is very random.In message , lightning writes
The fan neon is powered from the circuit that drives the fan relay coil
To test the APS, you need to get a meter and make sure you are getting low ohmic contacts between the common and normally open contacts
You can test this by (gently) sucking or blowing on one of the tubes attached to the APS several times and checking the resistance. Touch the meter probes together first so you can zero out the probe resistance
Problem finally identifies and resolved.
It turned out to be a split diaphragm in the air pressure switch.
It was the older style APS with external microswitch so it could be taken apart and inspected.
The new replacement is a moulded assembly.
Interestingly, the diaphragm is a cellophane type material and backed up with a steel washer.
The diaphragm had stuck to the washer adjacent to where the P1 connection was made to the switch. It looked like moisture had been introduced via the P1 pipe, caused the diaphragm to stick to the washer and every time it flexed the diaphragm was fatigued against the edge of the washer and finally split.
Thanks Geoff for your input
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