12 volt lighting system

i am experiencing problems with our 12 volt lighting system, the lights are cycling from bright to dim. I disconnected the battery to check it, the battery voltage appeared good (12 volts). the interior 12 volt lights were very dim while the battery was disconnected. Once the battery was reconnected the lighting resumed the cycling between bright and dim. Is my 12 volt power converter going out? :(
Re: 12 volt lighting system

When you disconnected your batteries and left the converter/charger powering your lights, you proved that the converter/charger was the problem.

The bright/dim cycle is the charger trying to charge your batteries, but having a problem doing it.


Senior Member
Re: 12 volt lighting system

Clearly there is a voltage variation, as that is what the lights are indicating. It would tell us more if we knew what the voltage was at in each case. Did you check it with a good quality digital meter? If so what does the voltage read when the lights are both bright and dim? Are you sure that the lights are not normal when dim and the voltage is going too high and so causing them to get brighter than normal?

The reaction of your converter with the battery disconnected would depend upon what type of converter you have. The Magnetec 6300, what was once most common does require a battery in the circuit to operate normally and to filter the power it puts out. To give a definite answer to your problem with only the knowledge that you post would be only a guess. Even so, I tend to agree with Tex that the most likely suspect is the converter.
RE: 12 volt lighting system

If you two sage hands are still looking: a new question...my generator kicks on fine but whatever switches that trip from 12 volt to 110 is not working., I can feel the generator "on" switch calling for the change but it still stays on 12v. Is the switch bad or is there another place to look on an '87 Allegro?

I'm new to this forum stuff so be gentle (my first time ya know?)

Re: 12 volt lighting system

my troubleshooting continues, today I disconnect the leads on the battery, the voltage showed 13.3, after reconnecting the battery I checked the voltage on the leads at the fuse box. The voltage shows 13.3. Something else when the cooling fan is on the converter it is showing 13.3 on the voltage, but the second it turns off the voltage drops to 10.7. Does the converter cycle on and off? If is does then the battery voltage is dropping when it is under load. The lights going bright to dim follows the voltage drop. This battery came with the fifth wheel. It is a 2006 Keystone challenger.


Senior Member
Re: 12 volt lighting system

Did ya check the fluid level in the battery? Maybe check each cell with the little ball floating tester. If ya got an extra battery try hooking it up. Just some thoughts.


Senior Member
Re: 12 volt lighting system

I just got my converter replaced today after we spent all day the other day in the shop and they could find nothing wrong my batteries went dead so we checked it again today and it was kicking on and off. Last week it was staying at 13 volts. I noticed over the past week since we had it checked that my voltage was slowly dropping by about 1 volt a day. But if I tapped the converter it would kick my battery up by a volt or two. Good luck to ya.