Hot Rads upstairs OR downstairs but not both together. Help

I also noticed that the temperature on the boiler is registering 80c + when supplying hot water. Despite it only being set to around 50. Not sure if this is related.

Not likely to be connected to radiators not heating fully ,but needs attention.

terryplumb said:

I have not read all the old posts , is the pump freely spinning and is it full of water ?

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Hi, as you've been so helpful previously I hope you don't mind me reaching out again.

With the colder weather coming I thought I better get on and fix this. Undid the front of the grundfos pump just now and when I place a screwdriver in the inner nut it is turning fine and water is coming out of it as expected.

I'm struggling to think what else it could be apart from the pump though. I'm debating to change it regardless and upgrade to the UPS3 or stick with the UPS.

Actually, I put the heating on tonight and the majority of the rads are cold both upstairs and downstairs. The ones that are first are on the run are getting hot but nothing else is. I'll order a replacement pump head tonight.