DIY Doctor UK DIY Forums

Any ideas why my Grundfos central heating pump doesn't operate? Boiler fires okay, then trips on boiler stat as the pump isn't operating. It is not airlocked just not working. Is it likely to be jammed or an electrical problem?

Could be either of those most probably stuck pump there is a slotted head screw on most (may be under a cover ) to free it (with power off)

if electrical then you need some method of confirming yes or no to the supply at the pump terminals

Thanks, took the bleed screw out completely and was able to rotate the impellor with a screwdriver as you said. I fully expected to have to replace the pump.