Thread: fusible link question

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Me neither. I hate ammeters. I left my mom a 79 ltd when I joined the army, but the cheap amps guage I installed failed catastrophically, and she was without a car. It was a good car, too.

I have read that using fusible links was not a good idea. The wiring kit I got from Ron Francis specifically says not to ever use a FL. I know they were used in older cars from the late 60's and early 70's but they stopped using them for a reason....just my .02

Originally Posted by chopt50wgn

I have read that using fusible links was not a good idea. The wiring kit I got from Ron Francis specifically says not to ever use a FL. I know they were used in older cars from the late 60's and early 70's but they stopped using them for a reason....just my .02

My wiring kit from EZ Wire included a fusible link, and their instructions were that it goes in the primary feed to the fuse block to prevent melt down and/or fire in the event of a dead short ahead of a fuse. I installed it.

you can buy it in rolls and it comes in different amp ratings and colors

A fusible link is more like a fail safe, it won't react as fast as a fuse, can handle more loading, but it will break before the wire it's attached to.

A 20 amp fuse will open right at 20 amps on average, sometimes 18 or 19 too. The fusible link will error on the other side and for a longer time. But it will open before the wire it is attached to. And they were usually installed as part of the feed to the power supply. I've seen them used to protect fuse panels too.

Like many things, they have a place to be used and a place they shouldn't.

A fuseable link is just a piece of wire 4 sizes smaller than what it is protecting #16 for #12. They use a better insulation than regular wire but that is all it is.

RS.. good memory, I had forgotten: the melted connections were on the steering column where the factory connector had been replaced with butt splices, using cheap crimpers. I had hoped it was the cause of the original failure of the fusible link.

I may have found the cause of the latest ( previous ) f.l. failure: the field wire brush on the alternator lost its screw. I found a replacement screw, and installed it with some blue locktite. Checked function, and the alternator is charging ok. Then I noticed the output terminal stud was rubbing into the heater hose, so I lopped off the end of the stud, beats me why they made it that long anyway.

Man, I'll bet you're about ready for this problem to be over with!! LOL..

There's no quick end to this project!

Although it is beginning to yield some progress.

I found why the fuel sending unit was leaking. The gasket managed to deform. Easy fix.

The dash lights are out resultant to a problem with the headlight dimmer. Not looking forward to pulling it, It's horribly placed.

The speedometer stopped clicking. I still might swap it out. Is there an easy fix for a noisy speedo?

What I really want is to strip it to a shell. I need a shop.

You gotta be careful when saying "Easy Fix".. things like dropping the tank to get to the sender turn into complete strap replacement 'cause you see how rusty or rotted the parts are.

Or you'll try to pull the speedo and all the fasteners strip or break off.. BTDT! 8-)

Noisy speedo.. I took the one out of my uncles 48 F-1 'cause the speedo was screaming, found a little copper cap with a wick under it. added oil and reinserted the cap. smooth as silk now. Not sure if that helps you but.. I tried! LOL..

I really need to just start a new thread for the steaming turd, but today brings more fun:
As for the sending unit, it's actually accessible from the side, no need to drop the tank. However, the tank is pretty beat up, so I'll probably swap in the one from the parts car in the future.

I got the headlight switch out, it looked ok. So I disassembled the pot, and hit it with some contact cleaner and a brass brush. Put it back in and voila, dash lights. Then I rewired the HEI with 12awg; can hardly believe the shop used 18awg. Also, they tapped power from the fuse box by jamming a spade connector into a fuse. I improved it with a brass fuse tap. Then I used a cheapie crimp on tap connector on the new ignition wire, to feed the volts guage. Found an Orange wire hanging, and a quick investigation showed it to be dash lamp circuit, so I routed it to feed the guage cluster under the dash. Using the parts car as reference, was able to I.D. the proper wire for the wiper washer pump.

I'm almost ready to risk driving it to work tomorrow.

Yes, this IS a long project.

Been driving it sparingly, mostly trouble free but the occasional hickup which tells me it is no daily driver.

I popped a 30 A fuse on the main line: the one replacing the fusible link.
So, I picked up a 40 A breaker to replace it, but haven't yet installed.

Today I put the battery charger on it, then started checking amp draw on the fuse, using my new digital clamp on. Looks like the line needs to hold forty amps.

These are the readings: headlights full power 20 A. Heater fan 5A. Wiper motor 7A.

Everything on was right at 30A.

The last time it popped was at night, raining, so I'm guessing the 30A fuse was just too small.

Do any of those amp readings seem excessive? I'm also going to guess that modern headlights draw more power.

What do you mean by "...on the main line"? If you're talking about he main power feed to your fuse block it needs to be a lot more than 30 to 40 amps, IMO. Consider that at night, headlights on, heater fan on high, wiper motor on, and now you hit the brakes, and perhaps with the turn signals flashing and you lay on the horn. Add to that the radio is cranked, and depending on what your running for speakers the amp is pulling up to 200 watts? Not sure you really want a breaker in that service, as with a dead short ahead of your fuse block the breaker will keep popping & resetting until it fails. Consider a maxi-fuse ahead of the fuse block, sized to handle the total capacity of the fuses & relays in the block. It's there only to protect against a catastrophic short that the fuses in the individual circuits cannot block.

You said back in post #14 that you were going to make the modifications to the wiring that were suggested in the article Ken posted. Did you do that, or are you still doing patchwork on the OEM approach that included the ammeter?

Duplicated due to a data base error.