Every once in a while the fan in my air handler trips the breaker on start up. I've replaced the breaker and capacitor. Its an old fan motor I suspect is getting hot. Thoughts?

Bated breath.

Fan motor going out? How old is old?

I would guess the capacitor, I would replace that first then if it keeps doing it then get a new fan motor.

A capacitor is really cheap

Already replaced.

15 years give or take. I can manage the replacement. Pretty straight forward.

It’s struggling on start up, meaning lack of electrical power or starting a mass from a dead stop, and there’s too much mass(dirty as heck) OR the bearings are seizing up a little. It doesn’t take much friction to keep them from getting going. Find out if there’s a hole for the lube and put some in IF they’re not sealed bearings

Single shaft or double?

Or if it’s a multi speed fan, and it’s on . . . Say medium, switch it to high. Could be the start windings have a bad spot, if the motor stops just in the right spot, trips the breaker.

Single shaft single speed.

OR. . . . . . it could be a breaker getting weak but not likely. What evap do you have?

It uses the same speed for heat as the AC?

I changed the breaker. This is a Goodman 2 ton unit.

I installed a hard start on the unit at my old house.

I highly doubt it's a weak breaker. As motors age they are not as efficient. I'd install the hard start if I was you.

Electric or gas heat?

It’s his inside unit.

You are officially in the weeds now

Electric.

Difference in a 240 or 120V motor.

Do you like apples?

touche

Bearings or bushings shot or dried up? Hard to turn?

Bob, just to be clear.

We are talking about the indoor unit? It is one of the breakers in indoor unit? What size is the breaker?

correct. 35 amp.

I would expect the motor would smoke before a 35 amp breaker would trip.
I also expect that 35 would feed the control transformer, blower motor and a heating element.
Before I condem motor, check for a burned wire(s) shorted to cabinet. Or between each other causing a phase to phase short. Or heating elements shorted phase to phase.

Because trip is eratic, visual inspection will be best.

Murphy's law prevails. If you want to talk, pm me your number.

I was just thinking this too. I wonder if it’s the circuit board type or the mechanical relay type. Could be one of those components. You’re right Lazyjack. Look for signs of wires that have gotten hot.