Paul;

I just finished wiring up my 4D Toplite Senso Multi and checking it out. Earlier just used it as a battery powered taillight due to inertia on my part. With the switch in the S position it acts as follows.

Any substantial movement of the bike turns it on, running on battery. If the bike is not moved further the light goes off after about 4 minutes.

Spinning the front wheel causes it to run on the generator. If done gently enough to not operate the motion sensor in the taillight then the battery operated standlight function did not come on when the front wheel stopped rotating. Apparently generator and battery operation work in conjunction with one another, influenced by the motion sensor electronics and presumably the ambient light sensor.

It sounds to me like you received a defective unit that does not have the motion sensor and time out electronics working. It could be defective electronics or a defective switch. No way to tell without schematics.

I hope that this is some help to you in determining where your problem lies.