When A/C was started for first time this year with furnace blower on automatic mode, we noticed the blower wasn't turning on along with the A/C.

After basic checks (power OK, fan motor turning freely, etc); I put the blower on continuous mode as a troubleshooting step to bypass any thermostat or controlled-related issues (and rule out a defective fan motor, which was replaced 2-3 years ago - furnace is 9 years old).

Now, even in continuous mode, the blower sometimes stops functioning after a few minutes - power to the attached electronic air filter is also cut when that happens. Other times the blower will stay on for hours until switched off.

Any advice on where to look or what to try next to troubleshoot the issue? Furnace model # is N9MP1075B12A

Try, before spending very much of your hard earned money, try replacing the capicitor with a new exact match, they are normally somewhere close to //or on the blower housing, cheapest thing to do on your own before calling out the expensive guys,called pro`s