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It sounds like you have Taco zone valves. If so that's where the voltage comes from. When the zone valves close they also close an end switch which calls in the pump and the burner. If you jump T & TV and the boiler finctions normally then the problem is not with the L8148.
Your not looking at this the right way. I'll help you diagnose this issue if you're willing to follow my advice. I have 40+ years experience installing and servicing hot water heating systems.