Booster pump won't start up...what to check?

[JimK]

My main pump did that this year. It means the bearings have probably seized up over the winter and the safeties in the pump switched it off to keep it from burning out. You'll need to find a way to break the main shaft loose so it can turn, but it may be noisy. You may need to replace the bearings.

Update 2:

It's alive!

While trying to unscrew the impeller, I got it freed up and it seemed to turn smoothly in both directions. Put everything back together and it started up fine this time. It's not running any noisier than normal, so hopefully that means its OK. I'll keep an eye on it and see how it does.

Thanks for the quick response, Carl.