Baxi Solo 3 Pump Continuously Running (Tried 2 Replacement PCB's)

[spacedmonkeys]

I have lived in this house with this boiler for 12 years now and have learned (after the first two times it happened) that a regular fault with the Baxi Solo 3 is the pcb going bad and the pump running constantly and the whirring annoying me at night.
Bought a spare (ebay) pcb 2 years ago and kept it in a cupboard, boxed, until needed. Ebay yes but to be fair the pcb looked unused. Well I got round to fitting it last weekend and within 5 minutes of fitting it I heard a clicking and the pump went off.
However the next day I noticed the pump was running again... Same issue... running constantly. So looks like the pcb may have already been on it's way out.... maybe?!
So took a chance and got a dirt cheap one off ebay again, "taken from a working boiler", so .. just fitted it... waited 10..20..30 minutes... pump still running
I guess I could just be unlucky with the 3 pcb's going bad... but I don't really want to spend £120 on a brand new PCB if there is another possible cause of the pump running constantly?
Pump itself has 3 positions. I've moved the switch between all three and the power seems to increase or decrease. So pump seems ok?
There is also an actuator, above the pump, which was replaced a year ago (no hot water was being generated).
One other cheap option I have is replacing the C16 Capacitor on the pcb. I heard this was the actual component that causes the pump issue.

However, aside from pcb, any suggestions as to what else could be causing this would be much appreciated.

 

[ianmcd]

your boiler needs a system by-pass are you sure that you have one ?

 

[Lower]

Maybe cheap ebay pcb's aren't the way forward....

I had the same boiler in our last house and had the same fault when the boiler was approx 8 years old. A brand new pcb fixed the fault and it didn't reoccur.

 

[picasso]

Is the pump connected to the boiler pcb or controlled by the zone valves ?

 

[CWHEATING]

Flow and return sensor problems maybe? Possibly, unsure? These types of situations I’d call up Baxi directly.

 

[spacedmonkeys]

your boiler needs a system by-pass are you sure that you have one ?

No idea, but replacing the pcb fixed the issue previously.

 

[spacedmonkeys]

Is the pump connected to the boiler pcb or controlled by the zone valves ?

100% controlled by the pcb

 

[spacedmonkeys]

There are some pcb "brand new" on ebay for a more sensible price than £120+ so I might just have to go that way

 

[Gasguru]

100% controlled by the pcb

Have you got a couple of zone valves and is a bypass fitted AND correctly set?

 

[spacedmonkeys]

Have you got a couple of zone valves and is a bypass fitted AND correctly set?

Don’t know I’m afraid, my skills go as far as changing the pcb

 

[Gasguru]

There's no point in swapping out pcbs until you know the boilers plumbed in properly...look at the manual and Google. The cast iron heat exchanger holds a significant amount of heat energy when the boiler shuts down and relies on the pump to dissipate that energy...if you've got 2 port valves without a bypass (or an incorrectly set one) the pump will run for a considerable time since the heats going no where.

 

[flameport]

So took a chance and got a dirt cheap one off ebay again, "taken from a working boiler"

The PCBs on ebay are taken from broken boilers. They will all have at least one fault, probably the most common one.
If you want a new one, get it from the manufacturer or a reputable supplier that does not sell on ebay.

Ebay is a place used almost exclusively to dispose of items that are used, defective, customer returns, factory rejects, counterfeit or all of the above.
The sort of stuff which previously would have gone straight in the bin.

 

[spacedmonkeys]

There's no point in swapping out pcbs until you know the boilers plumbed in properly...look at the manual and Google. The cast iron heat exchanger holds a significant amount of heat energy when the boiler shuts down and relies on the pump to dissipate that energy...if you've got 2 port valves without a bypass (or an incorrectly set one) the pump will run for a considerable time since the heats going no where.

Ok but if it’s been working ok for the 12 years I’ve been here and the only fault has been pcb two or three times and a gas valve once, it must be plumbed in ok?

 

[spacedmonkeys]

But as it is a known fault with the pcb I am hesitant to spend the money on a brand new one if the fault is still inherent in newer version pcb... hence buying 2nd hand in the past.

 

[ollski]

As above a sticking zone valve could cause it, check your zone valve wiring voltages when the pump is running of its own accord, shouldn't have power on either orange wire.