Replacing pool pump: wiring from breaker box through timer to pump acting strange.

[Calot Carter]

New member, DIY homeowner here.
I bought a new in-ground 1HP 120v Harris pool pump (online) and had it installed by my pool maintenance company. A few weeks later it appears blown -- it hums when the power goes on -- but I removed the back and the shaft turns easily so I suspect wiring issues.
There is an outside breaker that has 2 breakers, both supplied by 120v lines, both of which appear to go to the line terminals on the mechanical timer. One of the load sides of the timer goes to the pump terminal point, the other is not hooked up.
Testing the load side of the breakers, one was loose and the reading on my multimeter flicked in and out, so I swapped another double breaker and tested output.
The thing I don't understand:
When I installed the new breaker, before I attached the load lines, I flipped the house breaker back on to test the outside breaker output. As expected, I got 120 volts between each output and neutral. Testing between the breaker outputs I got 240 volts.
BUT -- when I attached the load lines -- without the pump wired yet -- and tested the output, I still get 120 volts between each breaker load side and neutral, but I no longer get 240 between the loads -- the meter reads zero.
When I test at the terminal point where the pump would be installed -- one black wire and one white wire -- I get 120 volts...BUT if I flip EITHER of the two breakers off, I still get 120 at the terminal.
Can this be right?
Thanks in advance.

 

[Megawatt]

New member, DIY homeowner here.
I bought a new in-ground 1HP 120v Harris pool pump (online) and had it installed by my pool maintenance company. A few weeks later it appears blown -- it hums when the power goes on -- but I removed the back and the shaft turns easily so I suspect wiring issues.
There is an outside breaker that has 2 breakers, both supplied by 120v lines, both of which appear to go to the line terminals on the mechanical timer. One of the load sides of the timer goes to the pump terminal point, the other is not hooked up.
Testing the load side of the breakers, one was loose and the reading on my multimeter flicked in and out, so I swapped another double breaker and tested output.
The thing I don't understand:
When I installed the new breaker, before I attached the load lines, I flipped the house breaker back on to test the outside breaker output. As expected, I got 120 volts between each output and neutral. Testing between the breaker outputs I got 240 volts.
BUT -- when I attached the load lines -- without the pump wired yet -- and tested the output, I still get 120 volts between each breaker load side and neutral, but I no longer get 240 between the loads -- the meter reads zero.
When I test at the terminal point where the pump would be installed -- one black wire and one white wire -- I get 120 volts...BUT if I flip EITHER of the two breakers off, I still get 120 at the terminal.
Can this be right?
Thanks in advance.

Carter you have me a little confused. If a motor ever hums you are looseing a phase and the motor is single phasing. When you say you have just 120vac are you reading both wires to neutral or ground or are you reading phase to phase which should give you 240vac