Baxi Solo 2 starting problem

[Boilermeister]

I have a start problem with a Baxi solo 2 50PF, "boiler on" light is on and no others. Pump runs, fan doesn't checked voltage across fan and none present. Checked resistance across thermistor (o.k@1M Ohm), across pillot solenoid (o.k @1.5kOhms) continuity across overheat stat (o.k) Also checked potentiometer and o.k at 0 and full range. Replaced pot and thermister just in case, no result, suspected board (already replaced 18 months ago), bought a service exchange for £40 and swapped out, still no joy.Now beginning to suspect fan motor....any suggestions or anyone had a similar fault, I haven't checked the loom yet but will do next before I think about fan replacement.

 

[Agile]

If there is no supply voltage across the fan I dont think you could reasonably expect it to be turning ( unless you wound up that rubber band! )

If you are not CORGI registered you are not expected to be delving inside the combustion chamber.

Tony

 

[Boilermeister]

Thanks for the advice Tony, I am not altering or modifying any of the combustion characteristics or breaking into the gas line and understand the fan requires a voltage to run! my point is why is there no voltage at the fan. As I understand it after the pump runs the fan starts and pressurises the plenhiem to operate the air switch, which in turn operates the ignition /pilot solenoid/main gas valve...although I may be missing something?

 

[undercover]

Be careful when working with 'live' electrics

check to see if you have 240v at the fans plug on the pcb.

you say you have checked the stats, have you checked the thermostat sensor

OOps - just re read and see you got 1Meg Ohm...

 

[Agile]

Were both thermistors 1 Meg cold?

Have you started by checking that there is a 240v supply on the call for heat connection to the boiler?

Tony

 

[Boilermeister]

1 Meg cold at thermistors, replaced the temp sensor anyhow, for the sake of £11 thought it was worth a punt, the switched live has 240v, I am reasonably comfortable working with LV electrics and work on industrial steam raising boilers for a living which have the same principles as a domestic.......albeit on a much larger scale, so ya think i'd be able to sort this !!!!!!

 

[undercover]

have you got voltage going to the fan from the pcb.

if yes then check continuity of fan wires

Could have a 2nd dud pcb

 

[Boilermeister]

No voltage at the fan, PCB replaced today with recon from CET, so although not entirely unfeasable, highly unlikely the PCB is a dud..unless a peripheral has caused the initial fault and blitzed the new board also...unlikely???

 

[undercover]

No voltage at the fan, PCB replaced today with recon from CET, so although not entirely unfeasable, highly unlikely the PCB is a dud..unless a peripheral has caused the initial fault and blitzed the new board also...unlikely???

to my earlier post. Have you got voltage at the fan connection AT THE pcb.

also have you tried to run the fan with a flying lead

In this job expect the unexpected

 

[Boilermeister]

No voltage at the PCB, checked continuity of harness, checked fan continuity, flying lead or test rig may be next option, is there another operation before the voltage to the fan that I may be overlooking, i.e does the board look at the pilot solenoid to ensure closed before applying voltage to the fan?

 

[gas4you]

Personally I would never trust or entertain buying a recon pcb of any sort.

 

[Mr Smyth]

Not 100% with this boiler....

Does the power for fan com via the air pressure switch.

Never quite sure about normally open (NO) and normally closed (NC). Doesn't 240 come from the PCB to common on the APS to start the fan via NC then the fan running correctly moves the APS to NO position and gives power to the gas valve. Or is it the other way round

Recently helped out a mate in distress who had changed 2 PCB's on a Performa still getting nowhere. Simply because his toooo quick diagnosis was no power to fan????? must be PCB

 

[undercover]

Not 100% with this boiler....

Does the power for fan com via the air pressure switch.

NO

Never quite sure about normally open (NO) and normally closed (NC). Doesn't 240 come from the PCB to common on the APS to start the fan via NC then the fan running correctly moves the APS to NO position and gives power to the gas valve. Or is it the other way round

Recently helped out a mate in distress who had changed 2 PCB's on a Performa still getting nowhere. Simply because his toooo quick diagnosis was no power to fan????? must be PCB

You need another pcb. you have power to the boiler and s/l. Stats check ok, fan checks ok, aps checks ok, pilot solenoid and gas valve checks ok.
no power on the pcb at fan terminals. Recon board is a dud.

 

[Boilermeister]

Thanks for the replies, take on board (no pun intended!)your comments regarding the PCB being a dud, however what are the chances of two boards, 1 only 14 months old and the other a recon both displaying the same fault modes, I measured the resistance again across the pilot solenoid and it returned 1.38kOhms should be 1.5kOhm, is this discrepancy enough to prevent the solenoid opening/closing thus preventing voltage to the fan from the board by not pulling in the fan relay??......starting to run out of ideas now, but may try the pilot sol next, any further advice welcomed

 

[Agile]

You are over thinking but under testing!

These are very simple PCBs.

Demand for heat
run pump
compare set temp with measured temp if apropriate initiate firing sequence
start fan STOP in your case!

Only after fan starts and is proved by APS is the first stage gas valve opened.

If fan not starting then there is a fault at an earlier stage.

I dont have time to look up the MI but its obviously something very simple!

Tony