pump not working (grundfosnselectric )

[falloverpete]

Hello,
My central heating was workong fine the yesterday but today, when i turned it on ( apollo boiler with thermostat 400 ) the pump wasn/t turning, normally when water and heating is selected, the pump turns and the boiler fires, however this time there was nothing. The timer still ticks away and the pilot light is lit. Would anyone be kind enough to provide an idea to what has gone wrong, possibly and any fault finding measures i could take? I did have an engineer round recently to replace the gas valve and i can't afford another £££ til next month.
ANy suggestions greatly appreciated
Fp

 

[falloverpete]

Latley, i have noticed a 'medicinal 'smell in the airing cupboard. I took the programmer off and it has 5 pins that connect to the wall mounted plastic frame. The frame is marked N L 1 2 3 4 for the wire conections. connection 3 has melted, the burnt plastic woudd account for the smell. I dont really understand why, although there has been some history with this boiler when the TV supressor had a power surge and blew up. I will replace the switchmaster unit, it was a 400 series, is there any problem with using a 300 series? The 400 series has two switches , ( timed, off , constant) and (water, heating and water ). However it's not cheap, and I wouldn't want it to suffer the same, quick, uninsured fate.
If anyone see's an error here, with what i'm doing, please let me know.
Thanks
FP