ST699 c/h programmer not working-help

A

angelf

My ST699 honeywell programmer just went last night. Replaced 3 amp fuse, & secured brown earth wire inside programmer which was loose-it started then blew again. Got a replacement ST699 today as circuit board was brown at bottom right hand corner of old programmer as u take it of the wall & turn it round to look at it. Again it started then same thing occurred. Any ideas on what is causing the fuse to blow? Any ideas on how to fix it? Boiler does start up each time. Am recently Corgi registered & would like to see if I could fix this problem myself. System is a basic gravity hot water/pumped c/h system with no room thermostats in house.
Any help would be appreciated. M
 
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Sounds like the pump. Disconnect the live in the pump and turn on the clock to prove. It may be leaking onto the contacts and shorting, blowing the fuse.
 
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My thoughts would lie with the pump or boiler fan (if it is fanned flue) but being a simple system like that the basic electrical checked done from the clock will pick up the problem im sure.
 
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A

angelf

have secured brown wire & put in another fuse clock now working & boiler is firing when on hot water only but blows again if c/h put on. Will look at pump now & let you know if it has been sorted.
Out of interest why would the live to the pump cause this problem?
M
 
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The fuse connected to the CH fused spur will blow because the the live from the pump has shorted to earth, basic electrics :(
 
A

angelf

THANKS FOR ALL YOUR HELP-the programmer was being used as a wiring centre & yes some wires were earthing out others. Thank you.

Mary :D
 

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