Thanks for your help thus far. I now need to test the motor load, repeatedly opening and closing a door, for hours, then days… How can I set up a circuit to cause the motor to reverse direction, automatically? I have many (momentary) N.O. / N.C. snap and push button switches. I do not currently have any latching/toggle switches, but could get them. I also have many automotive type relays available as well. I can acquire additional supplies as needed.

 

You need a timer that has programmable on time and off time.

What supply voltage do you have? If you have AC line voltage, many EBay timers would fit the bill. Use the timer to control a SPDT AC-line powered relay to replace the center off switch in your diagram, above. Effectively, the timer will be throwing the center-off switch.

The alternative is build a timer yourself, using a 555 astable oscillator or similar. If your DC supply is 24Vdc, then you will need to drop the voltage to <16V to operate a 555 timer.

 

You may have to keep the cycle time down, if continuously reversing for hours/days, you might see overheating of the motor, especially with no sophisticated motor controller, just relay on/off.
I would think that less time would be required to prove out the system, after this component failure can occur anyway.
Max.

 

Your timer needs to allow the motor to come to a stop before it switches to reverse direction, otherwise you risk damaging the motor.

 

Even then I see a lot of heating occurring due to across line starting if done too frequently. Hours/days.
Max.