Question about Honeywell International Honeywell Universal Electronic Fan Timer St9120u1003

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I can get the timer to start the boiler but it will not turn off its a hunnywell 20 years old with no serial number

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Hi there, first of all you can try a simple test which will determine if the thermostat is faulty or not. With the boiler turn on or off simply turn the thermostat clock wise then anti-clockwise can you hear a click sound when you do this? if yes then, the thermostat is probably okay and the problem maybe a stuck relay which would require you to open the control panel on the boiler, keep in mind that the power must be shut off before you do this to prevent any chance of an electric shock , if the thermostat does not make any sound at all , then chances are that the contact points are welded shut in the on position and would require you to open the thermostat and release them (power off of corse) do not attempt to do this with the power on, if you feel that you are unsure of trying this then please contact a tradesperson in your area, if not then this how to do it.
With the power off take the cover off the thermostat, inside you will see a bi-metal strip with two contact points , try turning the knob an watch this contact point and see if is in fact opening the circuit, if you see that it is stuck , find a small flat blade screw driver and gently pry them apart, once this is done , inspect the contact point and lightly file it using a nail file , try to keep it square to the points so as to create a fresh contact point , do this to both or all points you can see, gently blow away the filing dust and replace the cover, turn it all back on and try it again, if it still does the same thing then replacement is imminent in which case you may either buy the part yourself (now that you know how to open it or contact a trades person in your area.
I hope this information helps you , but if it is not what you wanted or would like to chat live , give me a shout I'm on as often as possible so maybe i can help you even more ..

Posted on May 12, 2009


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