I have a 92 CTD that is having a problem. The intake preheater all at once quit coming on and at the same time, the alternator isn't charging enough or something is draining a lot of current. It is only putting out 12.1 Volts since this occurred.

Has anyone had the same problem? If so, what was wrong and how was it fixed? I have a feeling that a relay might have gone out, but not sure. Any suggestions would be greatly appreciated!!! Thanks in advance!!!!