When circulator pump is hooked up to system the pump won't work. When hooked up to external electric power it works.

Track down the power leeds that supply the pump and they should go to a relay or other control. Then test that control to find your problem.

Track down the power leeds that supply the pump and they should go to a relay or other control. Then test that control to find your problem.

Thanks for the info, ended up replacing the relay and all is working fine, thanks again for you time and knowledge.

You got it fixed! Good deal.