Baxi 80e Combi - no central heating

[diy_darren]

Had a go at changing a radiator and installing a TRV and now I can't get the central heating to work

Drained the system as I had to alter the pipework. Fitted radiator, refilled system, bled radiators and refilled system up to 1 bar pressure (as indicated by dial on boiler).

- The boiler fires up and heats the hot water (from a tap) fine.
- Power is connected, the green on light is lit and no warning lights.
- Central heating temperature dial is about half way and the boiler is in central heating and hot water mode (dial on far left).

To start the central heating I've been lifting the switch fully up inside the built in timer dial on the right hand side of the boiler. The boiler doesn't fire up and I can't hear the pump working.

Any ideas what could be wrong?

 

[baxpoti]

Room stat/external controls calling for heat?

 

[diy_darren]

Room stat/external controls calling for heat?

There aren't any external controls, only the timer built into the boiler. How would I tell if that was calling for heat? I own a voltmeter, but don't claim to have much idea how to use it properly

 

[baxpoti]

Where the mains connects to the boiler is there a yellow wire linking terminals 1 and 2?

 

[diy_darren]

I've not checked terminals 1 and 2 yet as the boiler is in another house - hoping for some more advice before I go back to establish the problem.

I still have the original installation instructions in which I found a page detailing the timer setup (see picture).



Now I can see terminal 1 & 2 are wired to the timer and that is the circuit I need to test! I can see two options;

1) Disconnect the current timer and wire in a 230v switch to test if the current timer is faulty.

2) Use a voltmeter to see if the old switch is calling for heat.

I'm comfortable I could test a new switch, but I'd like to learn how to use a voltmeter as it seems the easiest and quickest test. Should I set the dial to 200 (about 11 o'clock on pic below)? Then where abouts should I touch the red/black probes of the voltmeter?

Thanks in advance!

 

[diy_darren]

I'll leave my previous reply to show the progression of the thread.

I've not checked terminals 1 and 2 yet as the boiler is in another house.

Checked the wiring and between terminals 1 & 2 is said yellow wire mentioned earlier. That kind of ruins my plans to test the switch by using a piece of wire between terminals 1 & 2 to bypass it

How does the boiler know it is using an integral timer and not an external one? Is it just because there is an integral one plugged in? Now I'm at a loss for a way to test the integral timer ...

I could undo the integral timer and see if I can just unplug it. Assuming that would bring the piece of yellow wire into play and call for heat constantly. Sound like a sensible way to carry on?

 

[baxpoti]

To bypass integral timer link the two black wires. 230v caution req'd.

 

[namsag]

To link wires remove clock and do it there if it still don`t work it may be the selector switch.

 

[baxpoti]

Have you got 230v on the yellow wire to earth and/or neutral?

 

[diy_darren]

OK, got access to the timer and pulled one black wire crimp connector free. Turned power back on to the boiler (timer began ticking again), touched the free crimp connector against the other black connector (still attached one) and nothing.

Tried removing the timer push connector from the PCB, turned power on to the boiler and nothing. Am not sure if the CH should have started in this case, but I thought it was worth a try without a timer connected.

In the above cases the left hand dial was set to CH and HW.

if it still don`t work it may be the selector switch.

Is there any way to test the switch or is it a process of elimination?

Have you got 230v on the yellow wire to earth and/or neutral?

Which wire/s should I be checking? I have brown, blue, yellow/green and the yellow wire connecting terminals 1 & 2. You want me to check blue and yellow with an electrical screwdriver or a voltmeter?

Thanks for sticking with this, although I'm getting out of my depth

 

[diy_darren]

Had to give up on the DIY efforts here and get a plumber in to look. He tested all the same bits as were suggested (and some more!) and thinks it may be the board. The advantage of him coming to that conclusion and not me is that if the new board isn't the solution he can return it with no charge.

 

[baxpoti]

PCB does sound favourite,
I'm suprised he can return it, if it proves to be something else!

 

[diy_darren]

I'm suprised he can return it, if it proves to be something else!

I was surprised when he told me that too. I assume it's because he knows the supplier well and they trust him not to damage the board when he fits/removes it.

If that wasn't the case I'd fit it myself and then cursed at the waste of £95 if it doesn't solve the problem

 

[diy_darren]

Picked up the new PCB from a local supplier today and the plumber said he didn't mind if I fitted it (probably because he doesn't do callout and was coming to me after his day of work as I only live a mile away from him).

New PCB was a bit different to the old one, but easy enough to fit. It's making it all fit under the casing again that's a pain! It fixed the problem anyway.

Really impressed with how helpful the plumber was. Will even give him a tip - surely a first

Thanks baxpoti and namsag for the advice. If nothing else I learnt how to use a continuity check to test a switch.

Final question - are there any companies out there that would recondition the old PCB or shall I just bin it?

 

[Agile]

Sounds like someone working on the side!

Be aware that anyone who does that is unlikely to be CORGi registered or insured.

The spare part was probably returned to his employer!!!

Tony