Worcester Heatslave 15/19 no hot water light

10 Feb 2010
Reaction score
United Kingdom
Hi Guys,

I hope some one can hep me PLEASE, I have a Worcester Heatslave 15/19, yesterday the hot water light wouldn't switch on, if I set the programmer to hot water on, the red light next to the LCD screen doesn't illuminate, my cold water pressure is good, the water pressure from the hot tap is good, the central heating is working fine & I've had no problems with lock outs, in fact the boiler has been running great for the past couple of years, I left it over night so that the system is cooled down & it's still the same, I have plenty of oil, the water pressure is at 1 bar, there is no rumbling noises coming from the boiler, the water pump & diverter valve are about 2 years old.

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Presume you've pressed SELECT a few times and watched the black bar descend from off, twice, once and on and the small rectangular red lamp stays off.....? The 'on' position should override any timer influence.
Sounds like a programmer fault to me I think but lets hear what the others say!
John :)
Hi John,

Thanks for replying so quickly.

Yes I've scrolled through it many times, there is no click as I scroll through no sound what so ever, might it be the flow check valve???, the 2amp fuse is good.

As you rightly say Kelvin, when you scroll down the scale, you should hear a click from a relay to make the boiler active and the small red light should come on. If it doesn't then the boiler remains asleep - but the other heating channel should work.
When you turn the hot tap on, you hear the flow switch click, which turns the burner on.....but it will only do this if the red lamp is lit (I think you still hear the click though).
One compensation if it is the programmer - it only has the one block connection into the pcb so replacement isn't difficult.
New programmers are quite expensive, unfortunately!
John :)
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Hi John,

My son has just come home, I've had him to turn on the hot water tap & I can hear a clicking sound as the hot water tap is turned on, would that indicate the flow switch is OK, if that's the case might it be the PCB is there any way of testing it before I go out & buy one.


remove the wire plug attatched to other end of flow switch & test with a test meter when you run a tap , check the flow switch using the audible beep test for continuity when the taps run (meter beeps) & stops when taps off
Hi John,

Yes I get a audible beep when the hot water tap runs & nothing with no water running, does this means it's likely to be the PCB.

I still think that red light has to be on before anything happens......I've found the PCB to be pretty robust on these but its maybe worth checking it for burning, and that the 3.15 amp slow blow fuse is intact.
I have found the buttons on the programmer get a bit huffy, but if the black bar is descending then that bit is ok. There are relays inside the programmer and I suspect one of those.
Mind you, I'm not an installer or boiler engineer - but I do have a 12/15 Heatslave in my holiday place......that needed a new programmer.
John :)
Hi Guys,

A quick update, I changed timer programmer PCB, & the problem was sorted so again thanks to this brilliant forum I had some great help & advice my boiler lives for another day.

:D :D :D


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