Hi, my outside air conditioning units fan runs then stops then runs again; is this normal? The house seems to be cooling fine.. I never noticed this before..

Does the fan motor have lubrication ports?

Some units will do this, as they have temp, pressure sensers that kick the fan on and off as necessary to cool the condenser. Im not familiar with trane products, so I can't say for sure if this is the case. I believe your best bet would be to contact a traine dealer in you area and ask them about your concerns. If this is not normal for your unit, you really should have a tech out to look into the problem. It could be a number of things, and only a trained professional can trouble shoot and cure the problem in short order. If you do find that this is not normal for your unit, and feel comfortable trouble shooting this yourself, I will do my best to help.

Most likely causes.

Unit designed this way.
Bad motor capacitor.
Bad motor.
Condenser coil extremely plugged. (not allowing enough airflow, in turn causing the blower motor to go out on overload from overheating.)