Impossible electrical conundrum!

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Jan 19, 2010 | 05:32 PM

Sycostang67

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From: Kuna ID

Impossible electrical conundrum!

I bought a bully brand fire strip to mount on the back of my tool box. When I plug it in on my bumper connection it works fine. My truck used to have a 5th wheel setup so there was trailer wiring in the bed already. I put a flat 4 plug and connect it to the fire strip and only 4 LEDS on it will work, the rest are very very dim. The funny thing is, the plug is already powering the amber marker lights on my tool box without issue. I check everything with a test light and everything is as it should be, got power on both sides of the plug all the way up to the fire strip. I cant find anything wrong, but for some stupid reason this fire strip wont work on the bed plug but will work on the bumper plug. I already have marker lights under my tailgate so I cant put the fire strip there.

Jan 19, 2010 | 07:22 PM

Sycostang67

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From: Kuna ID

I figured it out, something is wrong with the ground in the front plug. I added a ground wire from the plug to the tool box and the lights worked, but when shut off, they would make a clicking noise and my brake controller would flash an error code. I then removed the trucks ground wire from the setup and cut the wire from the fire strip plug and grounded it straight to the tool box and now everything works as it should.

Jan 19, 2010 | 07:27 PM

RV_Tech

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From: Bristol, TN.

Quote:

Originally Posted by Sycostang67

This is just a shot in the dark, but I never work with a test light as I can't get a voltage reading with one. I know they are fast and easy, but they just don't give me enough information in many situations. It sounds like you have a voltage drop somewhere. Most of the time when I get into things that seem strange I have a poor connection or a weak ground.

Steve

Jan 19, 2010 | 07:38 PM

Sycostang67

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From: Kuna ID

I used a voltmeter as well, I was getting just shy of 12 volts from each receptacle with the truck not running.

Jan 19, 2010 | 07:50 PM

RV_Tech

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From: Bristol, TN.

Quote:

Originally Posted by Sycostang67

I used a voltmeter as well, I was getting just shy of 12 volts from each receptacle with the truck not running.

Okay, let me make sure I am on the same page you are. Basically you have added a set of lights and everything now works on one power source, but will not work on another source? If I understand the situation, there has to be something different between the sources, as your lights are not changing. With the same voltage supply, there must be an increase in resistance somewhere in your feed. When you rule out what you know works, that is all I can see you have left. Your voltage is constant, but I bet your resistance varies between sources to your lights.

Steve

Jan 20, 2010 | 03:18 PM

Sycostang67

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From: Kuna ID

The lights that were already on the tool box are self grounding. The lights I added were grounded through the plug which is a flat 4 type trailer plug. When the plug was connected I tapped into the white wire and ran it to ground. What was weird is that it sparked when it touched ground, making me think it's hot. I cut the wire white fron the light side of the plug and ran it to ground to get it to work, leaving the truck side of the plug disconnected.

Jan 20, 2010 | 05:43 PM

81-F-150-Explorer

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From: Northern California

The ground will be "hot" so to speak, and can create sparks.

Here is why...

12 volts come from plus side of the battery, through the wires, enter the lamp through the power wire, lights the lamp, then 12 volts exit the lamp through the ground wire, through the body, back to the negative side of the battery. This completes the circut.

This is also why if you hook lamps up in series, if one goes out, they all go out. The first lamps ground connection is hooked to the second lamps plus connection, etc..., etc...

http://en.wikipedia.org/wiki/Series_...allel_circuits

Hope this explains that.