Losing voltage after accessory harness

[4everRS]

Hello all. I'm new here, so please let me know if I'm not following proper protocol.

I have a 2005 Harris Flotebote super sunliner 240. Last summer I started having intermittent electrical accessory problems. At random, many the accessories wouldn't work including lights, horn, and radio.

Earlier today I got under the dash with a voltmeter. On the main accessory harness coming up from under the deck, there is a power supply. When I have that harness unplugged, there is 12 volts at that incoming power supply. After I plug it in, it drops down to 3.8 volts. Also, every power supply has only 3.8 volts. The radio, switches, even the breakers. Only 3.8 volts.

Please give me your ideas. Thanks in advance.

 

[Grub54891]

Is the plug in good shape? If there is any corrosion, it would do that, or it's got a bad ground and you are reading a backfeed. You could run a temporary ground and see if it changes. Then repair from there. If it's in the power supply wire, you could run a temporary hot and see if it changes also. Check all connections including grounds at the battery, and motor to assure they are clean and shiney, I put a dab of dielectric grease on the connections to avoid corrosion.

 

[4everRS]

Thanks Grub. That plug looks good. There are about 7 wires going into, and out of it. I assume the ground is always black correct?

It seems as if all the switches (radio, lights, horn, acc) are wired in series. Is it possible that I have a bad switch? And is there a way to test that with my voltmeter?

Thanks again

 

[Silvertip]

Accessories are NOT wired in series. Each accessory should have a separate feed from the incoming 12 volt power supply. That power supply then branches through separate fuses and switches then on to the various accessories. The ground from each accessory goes back to the ground buss, wherever that may be. From there a large ground wire goes back to the battery.

 

[4everRS]

Thank you for the replies.

I've got it fixed. At the battery, there is an positive wire on the post that powers all the switches. It has an in line fuse. That fuse had quite a bit of corrosion on it. Once cleaned and ensured the connection was solid, everything works great. I used dielectric grease as well.

It fooled me pretty good as the switches were still showing voltage. However, as soon as any amperage was put in those lines(using the switches) voltage dropped to zero.

Thanks again for the replies.