The AC regulator could definitely be the problem. Its also has a semi smart smoke unit. Both solutions looking for a problem. Looks like you will need to pull the shell, then do some checking with a multimeter. First check the resistor. It should read 8 ohms. If you are lucky it reads infinity. Problem found. If it reads 8 ohms you have to power up the engine and see if there is voltage across the resistor.
If you are comfortable doing this OK, if not it may be time to send it out.
Pete