I have uploaded the service manual for your unit.
Please click here for the download.
There are schematics at the end of the manual.
Please let me know if you require more information.
No each systerm operates independantly from the others. The first thing I would check is the heating element. Check it for an open ohms reading (no continuity).
If you would like to confirm that it does operate on the other systems simply hook a set of jumper cables to your car and then to the units 12volt system.