Worcester Greenstar Heatslave 18/25 oil boiler

12 Dec 2015
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United Kingdom
Hi all, I have a Worcester Greenstar Heatslave 18/25 oil boiler that is faulty. Basically, the heating won't work when called for and the hot water only works when the boiler is given a tap/bang on the top. That said, once the boiler comes to life, with the heating selected and the hot water de-selected, the boiler is running but not heating the radiators. The boiler then stops and then restarts itself. Once this has happened the radiators start to heat up and the boiler seems to run fine. We had the boiler serviced in the spring but not used the central heating much since then I don't think. Any suggestion what the problem might be?
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Possible poor connection on timer or PCB. Isolate the boiler electrically and remake all connections to see if it is any better. Once it starts, it will serve heatstore first, then switch to heating. The pause is the motorised valve moving over.
Thanks for the reply oilhead. I will give that a try on my next day off.
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Thanks for the info Oilhead and confirmation Oilboffin. I took the cover off(after turning the supply off) and disconnected and remade all the connections but it still didn't sort the problem out. I bypassed the timer by connecting terminals 1 & 3(I think off the top of my head) and the heating came on. I did notice that on the back of the timer there are 2 black casings covering 2 solenoid type switches. If I tap these, depending on which I tap(1 does hot water and 1 does the heating) the heating and hot water will both work. Once these switches have both been activated the hot water will cut in and out when required and the heating can be controlled by the room thermostat. The timer needs to be set at On for this to work. If I have it on timed once or twice, when the timer tells it to cut out it will not restart again unless I go through the same routine. I take it the timer/programmer is faulty?
I have changed several of these timers. They are not the most reliable. The oil timer is 4 -5 times more expensive than the gas timer, which looks the same, but does not have the relays (the black boxes you have been tapping). If you replace with a remote programmer, look for onethat has a higher switching capacity than the usual 3 amps.
Thanks again for the reply. Yes I have noticed how more expensive the oil timers are. Which programmer would you recommend? Is it worth buying something like a hive or nest system(assuming they are compatible ).

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