Rear seat heater not working?

[DrMike]

I haven't used the rear seat heaters in my car yet, since my two kids have been in carseats since I've had the car. My daughter is finally tall enough to not need one, so I told her she would finally get to enjoy the heated seats. But it doesn't seem to come on. I turn it on on the max setting, and it doesn't heat up at all.

Is there a minimum weight limit to trigger it? Or do I need to schedule service?

Thanks!