My '91 300TE 4matic decided the fan wasn't necessary anymore.

I'm trying to change its mind. Can anybody tell me an easy to get at access point to determine if the fan is getting voltage? I know the system well enough to know the problem could be in the fan motor, the speed controller mounted on the motor, or even the pushbutton unit in the dash. I removed the fan motor, replaced the brushes and relubed the bearings last year so I know how to get the motor out. I'm just trying to make sure I don't fix the part that isn't broke.

Thanks!!