66 Fusible Link

[Doug C.]

In the Dec. 2004 issue of the Corvette Enthusiast there was an article about installing a fusible link on the main electrical circut of pre-67 vettes to prevent an electrical fire. It seems like a good idea. My question is: Would it be a better idea to install some sort of inline "maxi-fuse" unit in case a "road-side repair" is required, and if so what size of fuse would be required to replace a 14-gauge fusible link?
The car is driven about 3000mi/yr.

[Ed Jennings]

Re: 66 Fusible Link

I wrote that article and here's my take on that idea: If you have a short circuit in your system of sufficient magnitude to melt the fusible link, it for sure needs to be corrected prior to reconnecting power. Otherwise, it's sort of like putting a penney under a fuse at your house, only maybe worse.

As I mentioned in the article, you may want to carry a spare link with you, as it can be "field installed", but you have to be sure the fault is cleared first. The in-line fuse would make for a quicker repair, but chances are that you are going to have to do some major troubleshooting/repairs before reestablishing the circuit anyway.

[Doug C.]

Re: 66 Fusible Link

Ed, I don't disagree with any of the points you make in your article or your response to my post. Perhaps I should be more clear, My point was that once the problem has been located and repaired (which may or may not be a difficult repair) it would be a lot easier and quicker to replace a fuse than to locate a soldering gun, solder or crimp tool and connectors, etc. if you are not close to home. I've got nothing against using fusilbe link I just thought an in-line fuse was a viable alternative.
My only question remains what size fuse to use?

[Mike Cobine]

Re: 66 Fusible Link

Try this for finding the current and then you can figure a fuse.

http://www.engineeringtoolbox.com/33_730.html

In my experience, and definitely not what they teach in school, real world problems in a stock configuration come from opens and shorts. So while people work hard to find a correct fuse value, in practice I have found any above the amount you actually need will work. For example, if you have a circuit of tail lights, and you need 4 amps, any 10-amp, 15-amp, etc will work because it will allow your lights to stay on and in an actual failure (short), a 10-, 15-, or 20-amp fuse will all blow almost immediately.

Rarely do you deal with a excessive current situation that is not a short, such as drawing 13 amps instead of 9 amps, and in a short, you have maximum current which will blow almost any fuse.

If you modify the original design by installing a 200 watt amplifier and giant subwoofer, all bets are off.

I would NOT use a circuit breaker.




Engineering Toolbox

[Ed Jennings]

Re: 66 Fusible Link

Doug, I suspect that if a fuse would have served the same purpose, the electrical engineers at GM would have specified one. On the other hand, you never know when economy or production considerations will outweigh engineering and good sense. That said, keep in mind that the entire electrical system feeds through this circuit. You don't want a situation where the system is loaded up, ie lights, heater fan, horn, radio, etc, and start getting blown fuses when you apply the brakes. On the other hand, you want a fuse that will blow when the circuit gets shorted and blow quickly enough to protect the wiring. I suspect you would need a pretty big fuse.I think I've seen 60 amp fuses, and you might need one this large to withstand maximum loads. Most of the inline fuse holders, (plug in type, not the glass type) will hold more than 1 size fuse. Get one of the larger ones and maybe a 40, 50, 60 amp fuse. You may have to go to a place that sells heavy truck parts to get one that large. Install the smallest fuse and then load the circuit. Turn everything on, and then crank the engine at the same time. Do it a couple of times. If the fuse will hold the load, you're probably ok. I KNOW you're ok with the fusable link of the proper size.