I replaced the battery in my '01 SuperCrew this weekend and unfortunately, broke the positive terminal connector taking it off (was very corroded). Anyway, in replacing the broken connector I unwrapped a plastic cover marked "Fuseable Link" covering the wiring segment running from the positive terminal on the battery to the firewall. Inside was a pair of white wires. Here's my questions:

1. What is a "Fuseable Link", and/or what is it for?
2. Given that this segment of wire was pretty beat up, could I just replace it with a comparable piece of wire (i.e. 6awg) and ring connectors?
3. If I replace the "Fuseable Link" segment as noted in 2 above, do I create any issues/problems?

Anybody?

Mike

 

A fuseable link is a specially designed segment of wire that is designed to literally burn up/melt when there is too much current flowing through it. No you cant replace it with a regular wire. And im not even sure if its a good idea to splice fuseable links together....
-Patrick

 

Fuseable links are made of wire that is two gauges smaller than the wire/circuit they are protecting; e.g., a 12 Ga link for a circuit using 8 Ga wire. You can buy them at most NAPA, Advance Auto, Autozone, etc. stores. The link should have the wire gauge it is made of molded in to the thick part of the insulation. Replace only with the same gauge part.

 

You know, that's what I figured it was, a poor mans version of a fuse / breaker protected circuit. Forgive me, but what a piece of crap design. I guess using an in-line fuse or circuit breaker would have cost too much.

Ok, since my feelings about the design features of the Fuseable Link are now on the table, here's my next question.

1. At approximately what amperage does the stock fuseable link melt to terminate the connection (25, 40, 60 amp)?

I really don't have any interest replacing the "Fuseable Link" with another one, but would rather replace it with a highend piece of Stinger 4awg wire, ring terminals, and a waterproof ANL in-line fuse (just like the one I have protecting my JL Audio amp and stereo system), all of which I currently have on-hand. I know the OEM wire on both sides of the Fuseable Link is 6awg, but the Stinger 4awg wire shouldn't pose an issue so long as I get the right amperage fuse in it.

Anything thoughts on that idea?.

Mike

 

Fuseable links are designed to withstand surges that may far exceed their rated capacity. They act as a slo-blow fuse (e.g., like are used on electrical motors). A circuit with a 14 Ga fuseable link, technically, may only handle 20 to 25 Amps, but will handle close to 30 amps for a minute or more before the wire finally burns up. A 25 amp fuse, on the other hand, will blow in a few hundredths of a second at 26 amps. In other words, to handle these surges with a regular fuse, you have to over fuse the circuit. Some automotive charging circuits are designed this way (Late model Mustangs and Ranger P/Us come to mind), but all the branch circuits are sub-fused. You have to look at the big picture to know if it is safe. How lucky do you feel today?

 

Good information, thanks. I'm getting to where I need to be. So if I follow your line of dialog, a fuseable link like that in my truck could partially melt depending upon the amount and duation of the amperage spike? The link I have in my truck currently is 6awg wire from the positive battery terminal to two 12awg fuseable link wires, to 6awg onto the starter swtich at the firewall. So what's my meltdown point on that link?

Depending upon the size of the alternator in my Truck, could I reasonably fuse the link with a ANL fuse matching the max amperage output (under normal operating conditions) of my alternator? I've used that option several times to protect high end stereo system installs powered by alternaters operating at around 130 amps.

On a side note, I've now contacted three auto parts stores and two Ford Dealerships (parts, service, and service mangers), and Ford Customer Service in Detroit, and nobody has any info to share on the amperage limit of the Fuseable Link. You'd think I was asking for the design specs on the B-2 bomber!

 

Well the alternator has saftey devices, if you will, inside that are fed based on battery charge. So you alternator see's a signal of 14.7v at normal system operation, so it doesnt need to charge. It sees voltage drop to 14.3 (just a rough guess i dont know the actual number) so then it opens the charging solinoid and sends replacement voltage back to the battery. The alternator is constantly "turning on" and "off"

So i would assume that unless that transistor and solinoids go bad then you dont really have amperage spikes from the alternator. And transistors by nature, are considered life-time devices that dont have moving mechanical parts that wear out over time, like you would have in a relay.

You traditionally see amperage spikes from high draw applications, like some electric fans that take alot of amperage to get them to initially start spinning.

maybe some of this information can help you learn a little more about your system. Ill take a look on my ford service DVD and see if there is any information about amperage "boiling points" lol
-Patrick

 

The Ford service DVD indicates that there are 3 Fusible links labeled A, B, and C but doesnt offer any information about the specs on them.

So then i consolted my text book for my electrical class and it says this So then with the text book not giving me any helpful power rating real world numbers, i consulted google... Found a helpful website that says
(Click on the image for the entire website)


So basically still havent found any real world power ratings anywhere, but there is advice that i said all along, replace with OEM and your good to go

 

See above for comments. We're getting there....

Mike

 

well my only added on comment so far, is a CAPacitor can do more harm then good in the average higher end sound system. If your lights dim even with the CAP you arent doing any good at all.

Anti-CAP information (external link)

The only thing ive seen as conclusive information is you should look and see if there is an actual max amperage number stamped onto the fusible link insulation.
-Patrick

 

I actually thought about just biting the bullet and re-installing the OEM fuseable link. The problem with that option is that the Red Top Optima install I did with the high end Stinger terminal connectors (and related wire repositioning) has rendered the stock fuseable link way to long. Its now so long that I'm not sure I could actually cut enough 6awg wire off of both ends to make it short enough overall to work. An inline fuse is looking more like my only solution.

Mike

 

well unless you are seeing something im not, there is no reason other then cosmetic that having longer power wire by a few inches would be a bad thing....
-Patrick

 

Two useful links:

http://www.rbeelectronics.com/wtable.htm

http://www.powerstream.com/wire_size.htm

Load spikes on your charging system are the total of all the parallel loads that may simultaneously be applied. I.e., even though your stereo is fused, its total load is added to the load applied by, e.g., your heater fan that was left on high the last time you drove the truck, your headlights or DRLs that came on automatically (assuming you started up in the evening), the A/C compressor kicking in, the power seat you decided to adjust as soon as you got in to the car (maybe you were'nt the last person to drive the vehicle), etc. The voltage level was low after cranking the engine, so the regulater set the charge level at maximum. All this stuff levels out in a few seconds, but you need to withstand the initial surge.

Are we there yet?

 

No its not so much a cosmetic issue any more, but rather, one of space. The fuseable link section of this segment (i.e. what I cannot shorten) is approximately 7" long (including the splices and the black rectangular plastic cover which has to stay covering it). The total length of the stock wiring run is approximately 18". The new total length of the segment after modification would need to be just shy of 10", which would only leave just less than 2" on each each of the wire to try and turn two corners to the associated connections. I'm a little concerned, given how stiff (i.e. 'cheap') the stock wire is, that the very short ends of the wire would put quite a bit of stress on the connectors. I could help ease that stress slightly by putting a slight bend in the connector at the firewall, but it's still not optimal.

I am starting to agree though, that since I can't seem to find any useful amperage info about the fuseable link, using the OEM wire is looking like my last best option.

 

Ok, enough is enough. I finally gave in, bit the bullet, and re-used the stock fuseable link segment. I had to flip it end for end, cut off both ring terminals, resize both ends of the wire, and crip, solder and shrink tube both ends of the wire to make it work. I applied shrink tubing to the areas of the wire where the insulation was chewed up as well. Doesn't look as good (and clean) as I would have liked, but it fits, its in, and everything works as normal. Here's a pic of the final result.




Thanks for everyones help and feedback. As usual, the members of this site turned out to be a great sounding board to help me through this issue.

Mike