Electrical, new vent problem!

I am replacing my stock powered roof vent with an all-weather type (Max-Air) and when I had it all ready to go it did not work; checking my power wires I found only 5.2 volts dc at the leads????? I went to the breaker and the light for that fuse was lit so I took it out but it was still good and even was still powering the overhead light that was on. I replaced it with a new one anyway and the light remains lit!!!!!

I am even more puzzled now! BTW: a light on the same circuit is getting in excess of 12.0 vdc....

Can anyone offer suggestions, had this same issue?????

Thanks,

Ron

[Bill]

Ron -

According to the wiring diagram, the entire front roof (meaning the overhead fan and all the lights) are powered through a single 15-amp fuse, just as you suggested.

So now, try this. First, set things up so you can see the reduced voltage again, just as you described (5 or so volts). Now measure the voltage between the negative (ground) side of the fan connector, and the trailer frame. You may need an extension wire for your voltmeter probe, but that's not a big deal. You expect to see zero volts. If you see 7-odd volts, there is a bad ground in the lighting circuit. You'll have to follow the circuit along, checking each connection, until you find it. Since the other lights in the ceiling work OK (I think you said), the problem is most likely right there at the connection nest for the fan and its lights.

If the ground circuit looks good, it is time to check the 12-volt supply side of the circuit. Plug in shore power, turn off all the lights and the fan, and measure the voltage at the fan connector. It should be around 14 volts. Now turn each light on, one at a time. The voltage may drop a couple tenths, but not much. Finally, turn on the fan and again measure the voltage. Again, it might drop a couple tenths, but not much. Finally, turn on all the lights and the fan and measure.

If any one of these tests produces a drastically reduced voltage, then there is a bad connection somewhere in the supply side. If you find this, it is most likely in the connector right there at the fan location, so check this out first.

Let us know what you find.

By the way, when you say "the light remains lit !!!", you're not implying that you can't turn it off, are you? If that is the case, then the whole thing is miswired.

Bill