Fuse block killing current

[Black Snow Slide]

I bought a fuse block from West Marine.

http://www.westmarine.com/webapp/wc...=true&storeNum=5002&subdeptNum=9&classNum=295

I checked the wire going to the block and it is a strong 12 volts at the ring that connects to one of the four screws at the top. When I connect it to the fuse block voltage drops to 7 volts. I double checked and tripled checked all the connections. Everything is tight. I disconnect it and power is strong again at the ring on the positive wire.

I have used the same ground in all testing. Any clue as to what I am missing?

 

[fishrdan]

Re: Fuse block killing current

Is the fuse block mounted or hanging free? Are there any circuits connected to the fuse block? It sounds like there is a high resistance (maybe a few hundred ohms, guess???) short from the fuse blocks buss bar to ground and it's dropping 5 volts through this short. If it was a direct short to ground (which it does not sound like) you would be melting the feed wire of blowing the feed wire's fuse.

Try disconnecting circuits/fuses from the fuse block to see if this resolves the problem or un-mount the fuse block from where it's screwed down. I'd bet there is some point where the +12V buss bar is contacting ground in some fashion.

Also, what gauge wire is going to the fuse block and how tight are the crimp connections and battery connection. If your supply wire is too thin, crimps or battery connection loose, you could be dropping the voltage there,,, but this is only when power is being pulled through the fuse block and feeding the circuits.

 

[bruceb58]

Re: Fuse block killing current

It sounds like there is a high resistance (maybe a few hundred ohms, guess???) short from the fuse blocks buss bar to ground and it's dropping 5 volts through this short.

Not a chance of this being the problem.

I'd bet there is some point where the +12V buss bar is contacting ground in some fashion.

Also, not your problem

you could be dropping the voltage there,,, but this is only when power is being pulled through the fuse block and feeding the circuits.

Now you have it.



You do have a bad connection somewhere. Get out your meter and connect a long lead from your meter to the battery ground. You need to do this to get a good ground reference...otherwise you have no idea what you are measuring. Then measure the voltage at the positive bus of the new fuse panel and also measure to the ground bus. One or both of those will have your voltage drop. By measuring from the ground of the battery to the ground bus, you are measuring the voltage drop across the ground cabling to determine if there is a voltage drop across it.

 

[Silvertip]

Re: Fuse block killing current

Simple test - remove the fuses. If the voltage still drops, you have an issue with the mounting of the block. If its ok at that point -- install one fuse at a time until you see the drop again. That circuit is the issue.

 

[fishrdan]

Re: Fuse block killing current

Not a chance of this being the problem.

Also, not your problem.

Hate to disagree with you, but I have seen and trouble shot problems like I was describing. It's not a direct short, but a resistive path to ground that carries a portion of the voltage to ground. A resistive grounding material like saltwater, burned up plastic (carbon) or another semi-conductive material..

I was under the assumption (yeah I know about assuming) that no circuits were connected (like the post reads), and the reason I asked about circuits being connected and for them to be disconnected. Guess I should have worded my post more carefully. I meant to say, once all the circuits have been disconnected and/or the fuses pulled, the only thing left is voltage being lost at the fuse block... Which BTW, I have seen before,,, burned up plastic (carbon) that dumped a portion of the voltage to ground, cable crushed just enough to induce a resistive short, but not a direct short. Weird stuff but it happens...

If circuits are connected to the fuse block and drawing power, yeah, then it's in the wiring and connections,,, but then again, no mention of this in his post?

 

[bruceb58]

Re: Fuse block killing current

I was under the assumption (yeah I know about assuming) that no circuits were connected (like the post reads), and the reason I asked about circuits being connected and for them to be disconnected. Guess I should have worded my post more carefully. I meant to say, once all the circuits have been disconnected and/or the fuses pulled, the only thing left is voltage being lost at the fuse block... Which BTW, I have seen before,,, burned up plastic (carbon) that dumped a portion of the voltage to ground, cable crushed just enough to induce a resistive short, but not a direct short. Weird stuff but it happens...

If circuits are connected to the fuse block and drawing power, yeah, then it's in the wiring and connections,,, but then again, no mention of this in his post?

Yeah...I'll buy that! You are right that there was no explanation if there was a load on the circuit.

 

[Black Snow Slide]

Re: Fuse block killing current

Hi everyone... Once again thank you for the replies.

I don't have anything wired to the fuse bus. I have it screwed into a large plastic like board that all the other electric stuff is strewed. The power supply line going to it is 10ga.

I continued to mess with it yesterday afternoon and could not find any answers even when testing on a bench.

Last night I went to an Auto parts store and bought a diffrent type of fuse bus. It stated it's desighned for direct weather aplications so we will see. I will hook it up on Sunday and see how it goes.

My neighbore stopped by when I was in the shop with this fuse bus. Told him of the problem. He picked it up and laughed. He said, "Look.. Its made in china.. The metal probable is soo cheap that it cant even conduct electricity. " And he walked away. Maybe he has the answer..lol Will write back on Sunday night with outcome.

 

[bruceb58]

Re: Fuse block killing current

When you make your voltage measurements, make sure you do everything with reference to one ground. Like I said in my first post, I try to make the reference always at one point, the battery itself.