Early 210's use a very similar regulator (same electronics, different wiring harness) and this is a very common problem.

It usually first presents itself as a blower that works fine up to half-speed, then will blow no harder.

Apply full power to your fan motor by disconnecting the regulator and grounding the motor lead that went there. The other lead is battery voltage. If the motor runs at full speed, it is fine and the fault is almost certainly in your regulator.

There is a slight chance that the fault is in your pushbutton control module, but that chance is very, very slight.