DIY Doctor

Honeywell Servie Reminder Key Sequence

Postby cliffevans » Mon Dec 08, 2008 11:06 am

Hi - I have not long had my boiler serviced but the Honeywell control unit is now saying it needs a service and will only run for one hour at a time. Apparently this can be reset with a key sequence but annoyingly Honeywell don't supply this with the manual! Does anyone know the reset key sequence for a Honeywell ST6400S??

Many thanks.
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Simply Build It

Postby plumbbob » Tue Dec 09, 2008 12:29 am

I see the Honeywell website does a whole range of installer manuals online.

The manual for the ST9400S gives info on how to reset and turn off the Service Timer Function. Whether this works for yours or not.....

Go to "" and visit their downloads section for the manual.

Can't find a mention of the ST6400
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