720 on the fritz... electrically speaking

[BLUESTEAL]

I don’t know what happened. Left to get some more Holiday lights and got there with no issues, came out with the booty and went to start er’ up and nothin’! !, I had fuel and temp gauge at first then they went south for the winter! clock still works along with exterior lights, headlights, horn and interior light but no start. Gave the fuse box a look see and everybody’s solid.
     Got er’ towed home and replaced the guts of the ignition switch, thinkin’ it was time for a new one as it was acting up and is the original piece, but still nothin’. Checked all the related relays and found them to be in working order. I’m taking the starter to get checked out in the morning but I’m betting it’s good to go. Didn’t smell nothin, saw no smoke and heard nothing unusual, This has got me lost for an answer as to why it just quit, anybody have history with something like this?

[datzenmike]

Check near the positive battery cable for the fusible links. They are about 3 inches long and have plastic connectors on each end so they can be removed and replaced. There are 3, Two Green and a Black. One of the Greens powers only the lights. The other Green powers things that are on all the time like the brake lights, interior light, horn, and clock. This leaves the Black fusible link which goes to the ignition switch which selects where the power goes.

 

  No gauges and no start signal tells me that you may not even have power to the ignition switch and the likely cause is the fusible link. It may look melted, burned or just crispy. The outside insulation may be good but the wire inside melted.

[BLUESTEAL]

Now , with your invaluable help Mike, I’ve found the problem. The black wire fuseable link looks like a bad Frito, crispy and burned with the brass connector exposed. Luckily, cruising the offerings on E Bay I found the exact same one, used of course but much fresher than this crispy critter I’ve got. For 20 chits I’ll find out if this solves the problem in a few days.

    I have a question for you regarding this piece. What makes this a fuseable link, I’m kind of fuzzy on just how they work, why not just put a visible fuse where this thing is instead of a melted wire and connector. Would be much simpler/safer to me, but hey I don’t design vehicle electronic systems.

[datzenmike]

Good!!

 

Keep in mind that it may have blown for a reason like a short to ground so test that this is not the case or this one will blow also. 

 

 

A fusible link is unique in that the hypalon plastic coating will melt but not catch fire like all other insulations. The last thing you need is a fire. The advantage of a fusible link it it does not blow right away but take 4-5 seconds. This allows it to survive a temporary or accidental short to ground. It is, after all, basically a fuse so always replace with the same rating and always with a 'fusible link' and not just a black wire that may not protect.