Myson Midas SI Boiler Fault

[legionmort]

Hi Everyone,

I have a Myson Midas SI boiler which has a continuously running hot water pump (when hot water is selected in any form).

Have tried swapping the hot water inlet sensor with another (old) sensor, but it is no better - sensors read about 28k ohms, is this correct?

Have tried swapping main control board with another (old) board, but still the same.

LED 5 is on all the time as if hot water is being demanded.

Any ideas anyone?

Thanks (hopefully.)

 

[legionmort]

Ok Guys,

it looks like the air flow sensor is at fault.

Do any of you out there happen to have a spare one they would be willing to part with?

Thanks.

 

[gas_man_gaz]

bite the bullet n get a new boiler

 

[legionmort]

Hi gas_man_gaz,

would love to get a new boiler (have been looking at Worcester 30 cdi) but those plumber blokes appear to be wanting to take my eyes out. Especially annoying as I work on electrical gear (mv upto 11kv) and also gases and liquids (pipework and measurement etc.)

Might have to give in in the end though, but would prefer to repair it myself.

 

[mysteryman]

Look at the domestic flowswitch.

 

[Agile]

You can work on the DHW demand switch which is the likely cause.

You should not be touching the air switch though.

Watch out for PCBs in OCBs or PFCs.

If you are well qualified at what you do then you should be earning enough to pay for a gas registered person to fit you with a new boiler.

It must be nearly five years since I saw one of those still working.

Tony

 

[legionmort]

Thanks for the replies guys.

By DHW switch do you mean sensor?

The reason I ended up at the airflow switch was because, playing with it (connections etc.) intermittently switched the fan LEDs off and on and allowed the burner to fire.

Blew/sucked into airflow switch and airflow pipe and boiler now working (for the moment, but not sure for how long!)

Thanks again.

 

[Agile]

We cannot give you any advice on the air flow switch because it should only be touched by a competent boilerengineer.

You original complaint was the DHW pump staying on. That would often be caused by the DHW demand switch being stuck on.

The sensor is only to control the temperature.

Tony