Sime ecomfort. No hot water unless heating is on

[MK Heating]

From cold with no heating on, open hot water tap, plunger comes out of diverter valve, valve meets micro switch, switch makes, pump runs then... nothing. Doesn't go any further than that.

If the heating been on a while then warm water comes from the tap. Boiler doesn't fire though

The fact the pin is moving from the diverter freely suggests it's not that? Micro switch I've had out and tested to be sure. Coupled with the fact the pump runs I know that's ok.

Could it be the thermistor? That's where I've arrived at. Couldn't find the values anywhere to test it

Thank you in advance!

 

[AllyBongo]

You'll know roughly by testing thermistors without exact values. Is there a HW thermistor on this boiler? Sounds like ignition should be happening... Good luck, had a few Simes to work on! Parts cost a small fortune, if somethings big goes I usually look to replace the boiler

 

[jtsplumbing]

Does fan run ?

 

[MK Heating]

No fan no. Stops at pump running

 

[jtsplumbing]

According to fault chart its a faulty fan

 

[jtsplumbing]

Have you got voltage to fan ? if yes its the fan / If no check cable to fan does fan run for heating ??

 

[MK Heating]

Fan runs fine on the heating. The heating will run all day. It's just the hot water that it won't fire on.

Followed the fault finding chart to no avail. Is it a 2 sped fan?

 

[MK Heating]

Was thinking if it's a 2 speed fan then maybe the faster of the 2 has packed in. Booked to go and have a 2nd look at it tomorrow. More time spent but it's all experience isn't it

 

[jtsplumbing]

Probably better to speak to sime Tec wile your in front of unit so you can carry out checks and they can talk you through it could be a PCB fault

 

[MK Heating]

Update for anyone who searches this in the future.

Went back today and found when demand for heating or hot water is present and after the pump starts, the fan gets a few very short pulses of 240v, this continues with the duration of the pulses getting longer for about 5 mins before the fan eventually splutters to life. Once it's running it runs fine. The fan relay in the board however is roasting hot. New pcb is £302 from my supplier so recon ordered off eBay at customers request.

Will see how that goes when it arrives.