The tests shown confirmed that my pump still works without the Capacitor .The Original Bosch Capacitor is rated as follows: 3uF ( microfarad) +/- 10% b
320V ~DB -25/85 degree C . It measures Length 60 mm x Diameter 25 mm .
I wonder which is the correct Maplin or other Capacitor to replace the original. The model shown in my local Maplin shop in Dublin was too large and I also was unsure about the rating. Any further advice would be appreciated.

Brian, December 2013

Thanks for that Toptrish, at least I have central heating by starting the pump motor manually, curiously Maplin's online catalogue does not give the dimensions , whereas the paper catalogue in the shop did, but the capacitor offered was too long, I'll await an email reply from Maplin and try to get the correct size, failing that I will attach it as you say or find a second hand version.

Brian, December 2013

It is often difficult to get the correct components for replacement unless you deal with the pump manufacturers the maplin capacitor RG63T will work but if it does not fit you could always fasten it outside the terminal box just put some sleeving on the wires to protect them or if you know any plumbers they might have an old pump to obtain capacitor

toptrish, December 2013