We have a ~10 yr old AG unit. Seven weeks ago, we noticed the outside unit was running, but the fan was not turning. Oil was added. That worked for several weeks. Last week, the fan stopped again. The tech replaced the fan motor this time. Now, 5 days later, the fan is not turning again. Could something else be wrong that is causing the fan motor to go out? I hate to keep calling the same tech if they are unclear on how to fix the issue.
Any ideas?

If your compressor is running but the fan isn't, call out the guy who charged you to replace it.

Most likely, it's the run capacitor that's bad. Some AC's have separate run capacitors and others, like mine, are a dual round run capacitor, which assists the condenser fan (12.5 mfd) and the compressor motor (40 mfd). Very easy to check and replace either of these. A Fluke 16 Multimeter will be invaluable for the serious do-it-yourselfer. If you have a separate condenser fan run capacitor, then you also have a separate compressor motor run capacitor. Since run capacitors get a greater workout than start capacitors, they usually wear out faster. If your start capacitor starts to leak, get it replaced right away. They can blow up like a firecracker.

Best advice... call back the people that reploaced the motor. And do this before you have anyone else to look at it. If you have someone else look at it and they say it is a bad motor (which can happen, a new motor just goes bad) the company that put it in can say that the other people did something to it and there fore the warranty is invalid.

If he put a new fan motor in and didn't replace the capacitor, he's not much of a Tech...