It could be an internal fuse, or that the transformer is malfunctioning.

Before any dis-assembly/internal inspection, be sure that the unit in unplugged.

Good luck...

Hi again, There are not a lot of parts available for this model, There are rectifiers, diodes and circuit breakers. I do not have a manual for that particular model. I am curious that when you put your ohm meter on the leads you read nothing. Don't do that with the unit on! It could be circuit breakers, they are the grey things that have a terminal on each side, they are labeled Buss ( like the fuses) the terminals may be labeled "bat" or "aux" They are more like a fuse than a circuit breaker. Check them with you ohm meter. You have to open the unit to get to them and since you will have it open if it is not the breakers, check the diodes, which are transformer safety for polarity reversal. last you can check the transformer, it is a multitap so the primary would probably not be suspect since you have power to the fan and guages. My bet is on the breaker! Let me know how this works out and thanks for sticking with it. Hope this Fixsya!