Glow-Worm 24ci combi boiler FAN problem

[unfinishedsweet]

Hi there again, I have an issue with mentioned boiler. Actually fan doesn't work. The displayed fault code is F02 what according to the service manual says that is "Air flow, Fan, Air Pressure Switch".

I have checked the vent, it's clear and shouldn't cause a problems, therefore I've checked out the APS, seems to be alright.

Tho the fan doesn't spin I forced APS to start ignition and that's fine, the rest works but the fan still doesn't spin.

Thus I checked the direct current (DC) values on the fan's supply cable and there's nothing, sometimes just low voltage but for no longer than 0.5 second.

All symptoms tells me that the PCB is faulty. Of course I've checked all the wiring and also tried to connect fan to 9V battery (it caused some movement, but the DC from the battery is to low for this fan IMO).

The part is quite expensive so I'd like to confirm my opinion with you fellas before I buy it. Thank's in advance.

 

[sonray ltd]

did you check for power for the fan at the pcb or the fan ?
check h3 terminal on the pcb fan connections.

 

[unfinishedsweet]

I've checked the power both at H3 and at the FAN to ensure there's no problem with the wire. Same situation

 

[sonray ltd]

pointing to a pcb fault.

 

[unfinishedsweet]

are any other possible reasons? it's a 200 quid item, so I'd like to be sure

 

[sonray ltd]

continuity on harness - ok
no power to fan
no power on h3 to fan harness
pcb faulty.

 

[unfinishedsweet]

ok, I'm going to fit new PCP, once I finished I'll write the report here. Thank you for help

Fortunately new PCB solved the fan problem, unfortunately another problem has been discovered.

Maybe this is not very important, better if mention that the PCB I bought is slightly different to the old one. It's just newer version of a part signed as 7.0 while the old is 1.0. That caused some confusing with the power supply connection of particular equipment like fan or pump, but this has been solved.

When the boiler got to work I realized that analog programmer doesn't work at all. Therefore I looked inside to check some things.

Firstly I check with voltage meter mere programmer to ensure weather it does any work or not. I found out that power supply pair of cables (not sure if it were r+gr or y+w) has constant voltage DC 1.5V. In the OFF position DC 7.5V runs through second pair. In the ON pos. no power there.
Clock behaves exactly the same. Conclusions are that programmer works fine and the power signal has to be delivered to Controls Interface PCB that passes it to main PCB as a switch off signal. Only doubt was the difference of voltage on both pairs of wires. Tho ignored it cause the Contr. Interf. works digitally so that's possible IMO.

Secondly I removed by-pass from voltage free heating controls connection terminal (the one for external thermostat) and boiler was still running though. That was very strange for me as should switch itself off, shouldn't it?

The third test I have done was completely disconnecting the Controls Interface Board from Main PCB, this did not stop the boiler.

All points that the CI PCB has burnt out together with main PCB. The mains supply voltage on the CI is correct (AC ~230V). There are many sensible transistors on the CI that could be easily damaged by incorrect voltage.

My question is: does the Controls Interface Board switch the boiler by sending power to Main PCB or by disconnecting some circuit? If by sending I'm sure the CI is gone, unless problem lies somewhere else.

Also I'd like to add that wires on J15 connector are going upside while on J13 downside according to previous, original connection. I think it is possible to connect them on reverse way. I did not try it

Customer asserts that the analog programmer used to work before boiler gone for winter holiday rest. I cannot be 100% sure what he asserts.

What you guys think about it?