Ariston MicroCombi - timer stops when should fire up

[Stevewatson]

Have an Ariston Microcombi boiler (47-116-16) that has recently had the PCB, thermistors, and water inlet replaced after the PCB blew. The boiler now works fine, have heating and hot water. The boiler fires up fine when the switch on the timer is set to manual.

The timer ticks along just fine and keeps time absolutely fine. The issue is if I set the heating to come on with the timer. I have it set to come on at 6am, but, when the time comes, the timer just "sticks", and the heating doesn't fire up. So when I check the boiler at, say, 7am, the clock has stuck at 6 and the heating hasn't fired up. If I set it to manual, it'll fire up, and if I then flick it back to the timer position, it'll turn off when it's set to turn off. When I flick the timer switches all to the "off" position, the timer will run for 24 hours without losing a minute.

It's really irritating, as I've had the plumber out twice now (once to replace the PCB and associated parts and once to look into this), and he says he's done everything he can. Seems weird, but it's almost like if the boiler is warm, then the timer works - the plumber checked the timer while he was here working on the hot water, and he set the timer a few times and it seemed to work - but then, the boiler had already been running for the hot water.

I think I'll likely have to replace the timer, but I really don't want to call the plumber out again!

Thoughts?

 

[DP]

I think you need a proper heating engineer to fix the boiler.

One of the utterly difficult fault to fix is one that is not there when one is standing in front of the boiler. Fortunately your boiler does not work when it is time to get it running off the timer. Why can your guy not fix this elementary defect. Does he not have a multimeter or does he lack basic skills?

 

[Stevewatson]

He's checked everything over with a multimeter, adjusted gas pressure, and called Ariston for advice. I don't really question his abilities.

Same thing happened this morning - boiler timer set to come on at 6, at 6 the timer "stuck" and the heating didn't fire up. It also stopped making the usual ticking noise. At 7, I flicked the switch to the manual position - heating fired up fine, and timer started ticking away like normal.

This must indicate a faulty timer, surely? If I don't use it, and manually flick the switch, the boiler has no issues.