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-   -   No power to fuse block (https://forums.maxperformanceinc.com/forums/showthread.php?t=613878)

Sam Elm 10-17-2009 04:58 PM

No power to fuse block
 
I've reinstalled my dash, and check the lighting at every step of the way. I reattached the steering column, then went onto the light switch.
I left the light switch hooked up to the harness, until now. I unplugged it to put the light switch itself into the dash, and then plugged it back in. Hooked up neg battery cable, I then pulled "on" the light switch to test.
Interior lights went on for a short time, then went out. Fuse looks and tested fine. I used the voltmeter to check the fuse block for 12v, but don't get any power anywhere on the block.

Is there another fuse or fusible link somewhere that could have gone out?
Does the power for the fuse block go through the light switch?
Where should I test next?

Thanks for your help....

"QUICK-SILVER" 10-17-2009 05:44 PM

The fuse box receives power from two different wires. Part of the box should be hot all the time and part of it hot with the ignition switch on. It all comes through the firewall bulkhead connector from under the hood, then splices off to different places. The non-switched wiring that powers part of the fuse box also powers the headlight switch.

Fuse link wire protects the main power supply wire under the hood in case there's a short in circuits not protected by the fuse box; like headlights and ignition.
On lighting, headlights are the only ones protected by the fuse link only. Other lighting, like tail lights, courtesy lights, and dash lights have fuse box protection.

The headlight switch also has two hot wires going to it. The one for the headlights and another for front marker, tail, and dash. The dash lights have an extra fuse (smallest in box) that's only hot when the headlight switch is on. It's power comes through the tail light fuse, through headlight switch, back through small fuse, and then on to dash.

No power at all coming in, you'll need to check fuse links. They may not be obviously blown by looking. Insulation can remain intact on the ouside and the wire be melted/blown inside. If so, pull on them and they'll stretch like a rubber band if they're bown.

REMEMBER Something caused the fuse link to blow if it has. So you'll want to inspect where you've been working and make sure no hot wires have gotten pinched or shorted somehow. A simple short should have bown a fuse in the box as long as the properly rated fuses are installed. It usually takes something major in a supply wire or headlight wire to blow a fuse link.

Fuse links are usually bolted to or in the harness right behind the alternator. Some models have them down next to the starter. So hopefully they'll be up top. Horn relay is another popular location if you can't locate them right away.

Sam Elm 10-17-2009 08:21 PM

Quote:

Originally Posted by "QUICK-SILVER" (Post 3795927)

REMEMBER Something caused the fuse link to blow if it has. So you'll want to inspect where you've been working and make sure no hot wires have gotten pinched or shorted somehow. A simple short should have bown a fuse in the box as long as the properly rated fuses are installed. It usually takes something major in a supply wire or headlight wire to blow a fuse link.

Fuse links are usually bolted to or in the harness right behind the alternator. Some models have them down next to the starter. So hopefully they'll be up top. Horn relay is another popular location if you can't locate them right away.

Thanks for the reply. I'm definitely checking over what I've done, making sure nothing is pinched. There is no voltage to the headlight switch plug, so I'll take a look at the fusible links, as you said hopefully up on top of the engine. No voltage at the horn relay, either. The engine harness looks pretty bad, the previous owner has hacked it up and there's lots of tape. I guess he did that when he added HEI. I'll tear into the tape and see what's in there. I've had one (engine harness with HEI) on order from M&H for a while, but I checked and that'll be another 3 weeks before it gets here.

I've been using my classic wiring colored diagram, which is great, but doesn't show the fusible links. I went back to my old "black and white" diagrams, which actually spelled out where they are supposed to be.

Thanks again for your help...this forum is great!!


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