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Old 06-01-2012, 04:21 PM   #113
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Quote:
Originally Posted by teddyu View Post
Bflinn181,

Fusible links are protection from short circuits or intensely high current draws. In this case, they protect the generator (alternator) and the Battery Distribution Box. It is a "main buss" protector for items that USUALLY are connected directly to an un-isolatable power source, the battery.
A fusible link is typically wire 4 gauge sizes smaller than the rest of the wire, coated in fire resistant insulation. What makes that different than a properly sized fuse or circuit breaker? As I said earlier, a fuse would be easier to locate and diagnose when blown.
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Old 06-01-2012, 04:24 PM   #114
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We can't have that.
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Old 06-01-2012, 05:29 PM   #115
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Quote:
Originally Posted by BFlinn181 View Post
A fusible link is typically wire 4 gauge sizes smaller than the rest of the wire, coated in fire resistant insulation. What makes that different than a properly sized fuse or circuit breaker? As I said earlier, a fuse would be easier to locate and diagnose when blown.
Fusible link....another "hidden" application...
The typical 30 Amp RV pedistal is wired with 10 ga. wire, rated at...30 amps.
Industrious RV'er, wanting to get MORE powere from the 30 A pedistal, sees a fantastic device, for just a few bucks, that allows you to connect BOTH the 30, and the 20 amp outlets together into one plug to now supply your 30 amp wired RV with...50 amps...
Remember the 10 gauge wire was rated for 30 amps...npw innocence hits the wire with 40, 45, or eve 50 amps....WAH-lah....FUSIBLE LINK!
Honked off Rv'er now complains that CG owner has junk electrical service...
Underground fusible link....I replaced a LOT of wire in out 7 years of CG ownership!! LOL....
Have fun!
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Old 06-01-2012, 06:26 PM   #116
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Ding, Ding, Ding we have a winner!

First of all I want to thank the forum especially Dave78Chief, Dunner and teddyu. Without your help I would still be lost. It turns out that I had a loose starter control feed wire at the starter relay located near the Degas tank. I became suspicious when I metered the supply cable into the distribution box under the hood and got voltage readings from under 2 to about 5 volts. I knew these readings were too low so I decided to remove the starter relay to see if it needed replacing. As I was removing the starter relay I noticed that the starter control feed wire located at the top of the relay (the one with the cut lines on the rubber boot) looked like it was on, but it was barely touching the post on the relay. I pushed it back on solidly and the engine fired right up. All the lost functions; horn, turn signals, lights, jacks, radio etc... are working perfectly. By the way, accessing the relay from under the MH is way easier than removing the Degas bottle and air deflector from the front of the MH, I know, I did it both ways.

Thanks again, you guys saved me money and tons of aggravation.

Tony
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Old 06-01-2012, 06:41 PM   #117
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Congrats Tony. From what angle was that picture taken.

Glad you found it. I know I learned a few things in this thread.
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Old 06-01-2012, 06:57 PM   #118
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Happy to hear you solved the issue! I hope others will learn from this, I know I did!
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Old 06-01-2012, 07:22 PM   #119
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Dunner, I took that picture while sitting between the Passenger front tire and the frame rail looking up. The relay is about 3' up from the ground attached to a vertical frame member on the right side of the radiator.

Thanks again, Tony
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Old 06-01-2012, 07:41 PM   #120
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Glad I could help however I am not convinced you fixed the problem but rather achieved a coincidental fix. The wire you pushed back on is only used to energize the relay and could only prevent the starter from working. I suspect you disturbed one of the other 4 small wires (fusible links) and it is now making contact again. The problem may very well come back with heat and vibration. I do recommend you get a pair of 12 gauge fusible links to keep in your back pocket The suspect wire pair will have grey terminals at the relay and the other end of the pair will attach to a black with orange strip 6 gauge wire.

A fusible link is a slo-blow protective circuit. It can handle short bursts of current above the rated current without opening. Normal fuses will open if the rating is reached.
http://www.madelectrical.com/catalog/fusible-link.shtml

Later model vehicles are migrating to MAXI fuses which exhibit the same characteristics as a fusible link. A 20A MAXI fuse subjected to a 100 amp overload current will open in about 0.5 seconds. That same 20A MAXI fuse will last 15 seconds for a 40 amp overload current.
http://www.littelfuse.de/data/de/Product_Catalogs/AUTOFUSEOLOGY.pdf

Fuse selection though has to be based on total circuit current requirements. The offending F53 circuit in this thread uses two 12 gauge fusible links connected in parallel thereby doubling the current carrying capacity of a single fusible link. Rub is, there is no clear cut translation of fusible link wire size to amperage rating. The rule of thumb is the fusible link should be 4 gauges smaller than the wire it is protecting. (8 gauge wire would use a 12 gauge fusible link).

Dave
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Old 06-01-2012, 07:53 PM   #121
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Thx Tony. Will check tomorrow. Too hot(112°) right now.
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Old 06-01-2012, 07:58 PM   #122
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Dave, Good advice on getting a pair of 12ga fusible links. I think I will do just that. I didn't mention; for the sake of brevity, that the right nut under the rubber insulators was loose also. I could turn it with my fingers. Fingers crossed, I think between the feed wire and the loose nut my problem has been located.

Tony
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Old 06-01-2012, 08:03 PM   #123
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Ahh, now that would do it!

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Old 06-01-2012, 08:24 PM   #124
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Dave, thanks for the great links on fusible links. I read the first one and thought I would post a portion that I found interesting and might help someone else in the future when dealing with fusible links:

NOTES about Fusible Links Only a serious short will cause a Fusible Link to burn–it disconnects a circuit from power just before the rest of the wiring in a circuit would be damaged. Momentary overloads will not burn out a Fusible Link–such as arcing a wrench between ground and an exposed terminal.
The insulation of the Fusible Link wire is soft and non-flammable, sometimes the conductor strands within will burn without noticeable damage to the insulation. A good test is to try stretching it. If it stretches like a rubber band then the wire within has burned out.

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Old 06-02-2012, 09:21 AM   #125
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This is why IRV2 is my "Go To" favoriate Forum. You all saved the OP big bucks in helping him locate and fix the problem. Hats off to all of you.
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Old 06-02-2012, 10:01 AM   #126
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2004 F53 Start Relay & Fusible Links

I found it! I found it! Thx Tony.

Just about straight up from the front of the right front wheel well. If it was a snake, it would
have bitten me every time I put my tire covers on.

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