Grant Vortex Combi 26 no Central Heating

28 Aug 2011
Reaction score
United Kingdom
Evening all, my external oil Grant vortex combi 26 boiler (from 2010) is giving no central heating, hot water ok, flow switch LED goes on/off with hot water, water pressure ok, about 1.5bar, Central Heat Pump and demand LED shows when thermostat turns on so looks like it's getting thermostat commands and telling the pump to start, might it be the motor or the control PCB?

It's regularly serviced and has parts replaced on a semi regular basis as it's so unreliable (2 flow switches, 2 expansion vessels, 2 on-off switches)

I'm good with electronics so happy to try diagnos and replace a PCB or something that won't cause explosions , any thoughts / checks I can try?

Many thanks for any help.
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Check the relay contacts, they often go intermittent on the pump contacts. The CH and DHW control PCBs often seem to fail too. Check out the installer manual it has all the wiring diagrams in.
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Update - it worked this morning all on its own! typical - So off with the lid and I found that wiggling the cable where it goes into the CH pump made the pump stop/start so prised off the black cover on top of motor and found the rotary switch (speed1,2,3) had some dark pitted marks suggesting it was arcing and a little piece of plastic had come off the dial. I tensioned the metal contact and cleaned all contacts and now it seems to work all the time. I can't see this item seperately available so guess I need a new motor if the control switch finally packs up for good.

Oh and for good measure the mains switch failed for the third or fourth time, they get stuck on the ON position due to heat, luckily I found a supply of genuine cheap replacements from CPC Farnell for £3 each and they're from the same maker as if you buy from Grant at £8 to £11

Thanks for all assistance guys.

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