worcester 9.24 c/h problems

[mmalone]

Guys, got a worcester 9.24 (47-311-07) with the old relay and 1 circuit board, not the one with 2 boards !!

The problem im advised is intermitting, the boiler will not always fire on demand for central heating, but if the customer runs the hot water this activates the boiler and the c/h stays on after tap is run, went to this today and it worked ok, at first it didnt and had to do as customer did but only done this once and couldnt find any faults ??

anyone else had this or can advise ?? initial thoughts were pcb or the relay but more swaying to the pcb, possibly a stickingrelay in the main pcb ??

did notice also that the molex connector to the c/h selector knob was disconnected but customer has advised this fault only started recently and no one has been at boiler recently so discounted this also !

 

[mmalone]

anyone ?? looking for some quick help on this to advise customer ! thanks

 

[ollski]

Would be tempted to make sure the aps is switching as I get a lot of problems on these to slow and failing fans. Not alot you can do if the fault isn't there when you test though. How far into the sequence did it get when you had it failing?

 

[mmalone]

Would be tempted to make sure the aps is switching as I get a lot of problems on these to slow and failing fans. Not alot you can do if the fault isn't there when you test though. How far into the sequence did it get when you had it failing?

first time i attempted to fire just the c/h mate, pump started fan just stayed on slow speed for pilot, no futher sequence..

if you run the h/w it fires every time if c/h is on demand also it then stays on for the c/h

never had this fault before but thinking the c/h demand must go through another part of the pcb and possibly intermitting on this or a relay ??

this is the first 1 ive worked on with just 1 pcb and the large rellay so dont want to be spending bucks on something that may not be the problem !