Baxi solo 2 50 pf not starting

[Smasher67]

Here's one for the Baxi experts:

I've got a Baxi solo 2 pf 50 that will not start. It was running fine until last week when it caused the electricity to trip. When the electric was turned back on the pump was on constantly and the boiler would not start.

When the boiler is turned on the 'boiler on' light comes on. There's no other lights lit. There's no fan, no pilot ticking nothing runs except the pump.

Assuming it was the programmer, which was very long in the tooth and needed replacement anyway, I replaced this with a new one, carefully following the wiring from the old one. No change.

After stripping down the boiler I saw one of the relays (the one behind the control pot', which looks like it controls the fan) had blown and bust the track on the board, . I replaced this and repaired the track but same problem. Next assumption - the PCB. I ordered a new PCB, carefully wired it in and same problem again except that the pump turns off now after about 8 mins so getting closer.

I've checked the pilot solenoid - 1.5k ohms and the gas valve. The fan read 59 ohms. The wiring has been checked to the fan, fan pressure switch, thermostat, etc. Are there any other tests I can perform to diagnose this?

I'm running out of ideas, can anyone help please or will I have to call a corgi?

Thanks

 

[Agile]

Is there an overheat stat which has tripped?

Did you check the continuity of the leads to the fan?

It seems odd that the track on the PCB blew without any sign of the real overcurrent cause.

I think you should check the periferals very carefully before the new pcb blows.

Tony

 

[Smasher67]

Thanks for your reply Tony. The boiler has never overheated. I checked the leads to the fan for continuity and these were good as were the ones to the pressure switch.

I will check the overheat stat next, the one on my boiler appears different to the schematic on partsarena as it connects directly to the boiler rather than clipped to the the pipe. Should this stat be open circuit if the boiler is not overheating?

There was a noise previously to the failure which was like a contstant ticker-ticker-ticker but I'm not sure if the was the old mechanical programmer or a relay on the board.

I'll check everything again later and record voltages out to the fan, pilot solenoid etc.

Thanks again.

 

[Agile]

The overheat stat is normally closed.

Tony

 

[baxpoti]

Check the voltage on the switched live

 

[Smasher67]

Thanks for all your suggestions. Here are my findings:

Overheat stat - continuity checked ok, tried removing wire and the boiler registered an overheat. Reconnected then powered it down and back up again. no change.

Readings taken when trying to start:
switched live is reading 240VAC.
solenoids 0V, 5k gas valve, 1.5k pilot.
Motor 0V, 50 ohms.
Thermostat open circuit. Tried bridging two wire but no change.

All wiring checked for continuity, connections cleaned up to fan/pressure switch connector.

Very strange. Has anyone got anything I can try? Its getting colder

 

[Smasher67]

I'm at a complete loss with this. Does anyone have anything I could try or any further tests that I could carry out?

 

[baxpoti]

Please confirm the following, there is something very obvious being missed!

Boiler on neon is the only light lit?

There is a permanent AND switched live feed to the boiler?

Pump is running and controlled by the PCB?

Fan is not running and has no feed to it?
(test at the terminal block above the fan on the incoming side)

Orange and yellow wires are on the correct PCB connections?
(yellow wires to back corner)

Have you tested the potentiometer as per the installation instructions?

 

[Smasher67]

It's a bloody tough one isn't it?

Boiler neon is the only light lit.
There is permanent and switched live to the boiler.
The pump is running and it is being controlled by the PCB. It continues to run for 5 or 10 mins when programmer goes off, which it should.
The fan is not running and there is no voltage to it. I've checked the voltage on terminal block and buzzed through to board when powered off to check wiring.
Orange and yellow wires are located correctly.

The potentiometer was already on the new board. I checked the connections were the same as on the old pcb. I will check this next with a meter as per the installation manual fault finding section just to eliminate this.

 

[gas4you]

Never assume a new part is working correctly. I would take the pcb back and get a replacement under warranty.

 

[baxpoti]

It was running fine until last week when it caused the electricity to trip

Did you find out the cause of this initial problem?

 

[Smasher67]

the black relay directly behind the pot had blown on the pcb, which I assume caused the power to trip on the comsumer unit. The relay problem is quite a common fault on these boilers I understand.

 

[Smasher67]

all done and dusted thanks for your help.

it was the thermostat sensor

 

[Jezzy]

I know this was 3 years ago, but at the end you said it was the relay on the board behind the pot, and then you put that it was the thermostat sensor, which is clipped to one of the pipes at the RHS. Which was it? Was it the board or the T/Stat sensor?
I have the exact same problem on one for a customer. It is making a ticking noise when the boiler is reset. I changed the sensor today. It was reading 1.5kohms before i put it on the boiler. The one i took off was not giving any reading, so i thought i had got it, but it still won't start the fan running and is still ticking.
Is it the PCB? and could that have taken out the new T/stat sensor too?
Any help would be appreciated.

 

[Smasher67]

Hi, it turned out to be the board AND the stat. I'm pretty sure that the board fault affected the stat.

I hope this helps.

Cheers[/b]