How did you "bypass the thermostat"? Is there electricity being supplied to the fan? There's not enough information here to provide any assistance.

Ok, Kurto,

Yes, there is a live wire connceted to a thermostst, which runs from thermostat to the unit. Sp I disconnceted the wire to the thermostat,, and unconnceted the wires from the unit to the thermosts; and I would gather, the unit should come on with a constant power source? It doesnt; so I think that tells me, the thermoststa isnt bad, but the fan.

Am I incorrect?

Most attic fans with a motor problem can probably be fixed without ripping into the roof. You should ask yourself if you need the fan anyway. They are usually not a good idea.

Well, per your description, you "disconnceted the wire to the thermostat" (doesn't say which wire), and "unconnceted the wires from the unit to the thermostats", which I'm guessing means that nothing is connected to anything. I agree that if you somehow connected a 120VAC power source that the fan should run.

If not, it's probably time to replace the fan, or as ionized suggests, patch the hole in the roof.

I had my fan motor freeze up. I bought a new motor and installed it. No roof patching required.

To bypass the thermostat you remove the wires from the thermostat and then wire nut them together. Now you have a continuous wire without a thermostat.