Honeywell ST6400C - keeps turning off immediately

[wingers]

Hi

I have an oil fired boiler with the honeywell st6400c controller

When I press the extra hour button to get just a hour of heat in evening it turns on then immediately off again, if I keep pressing it, eventually it will stay on

Any thoughts please?

 

[45yearsagasman]

Replace your faulty programmer.

 

[wingers]

Replace your faulty programmer.

didn't know the controller was the cause, hence me asking!

So I assume you think that is the cause? it is 2 channel and the hot water program works fine, so could just 1 of the channels fail like that?

Any tips on replacement would be handy

 

[nickpat]

I have the same problem in which the 6400C cannot switch on the heating but controls the hot water perfectly.

I am planning to replace it with an ST9400C. I understand the 9400 fits on to the same wiring backplate. Is there anything I should look out for in the replacement?

 

[wingers]

hi nickpat

I replaced mine with the st9400c too - and it works really well now - just remember to make note of any "engineers" settings on the old controller - so yout can set the new controller the same - things such as cycle rate etc

And yes it does fit onto same back plate, just two screws, clip old one off and put new one on - put screws back and it works