Double problem - Baxi 105

[brook877]

Hi all, I'm hoping someone can help me understand a problem, actually two problems I'm having with my boiler.

The boiler is an older Baxi 105, its had it's share of problems, some of which I've been able to repair, (PCB, diaphragm, fan etc) some I've had to get someone to action the repair for me.

But I've always been able to understand the issue..

But I'm stumped on this occasion.

Problem 1-
No hot water when in water only setting, the diaphragm moves and the micro switch is flicked, bit I get "fault on pump" fault light.

Problem 2-
Following a reset I can get the boiler to work in central heating mode, and this gives me hot water, but the system pressure keeps rising and within an hour the gauge is into the red..

I'm grateful for any thoughts or advice.

 

[Madrab]

Problem 2 will probably be the expansion vessel (EV), needs the internal EV checked to see if it just needs a re-charge or if the inner membrane has split and needs replaced or an external vessel fitted.

problem one could be several things - needs an onsite diagnosis.

Get someone in to service to fix the EV and fault find at the same time.

 

[brook877]

I'm confused by the 2 faults appearing at the same time, I can't come up with a fault that would cause both issues, but having 2 unconnected faults appear at the same time seems unlikely.

Is there any component that could be effected by having a faulty EV that would cause my second issue?

 

[DP]

Check pump capacitor value is within tolerance.

Pump differential in CH mode is good so the flow spindle pushes up to operate the microswitch.

Put the boiler in ch mode, while watching the spindle, get someone to run a hot tap. Spindle should stay in place and boiler deliver hot water unless the differential pressure is really poor

I would strip the flow manifold, fit new ( genuine) diaphragm, clean and lub the spindle, ensure the orifice is clear

Cracking boiler that responds well to proper service. Not many boilers that are this reliable