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Amperage Rating For Fusible Link.

 
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/6 Matt
TBI Slant 6


Joined: 09 Jan 2010
Posts: 187
Location: Burke County, North Carolina

Post subject: Amperage Rating For Fusible Link. (Sat Jul 17, 2010 1:04 pm) Reply with quote

How much current would a fusible link carry in my Dart pictured below? Electrical is completely stock.



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1970 Dodge Dart Swinger 225 slant, 3 speed auto, 7-1/4 open rear with 3.55 gears. 003 SS Leaf Springs. 1973 Factory spec electronic ignition upgrade, Nippondenso mini-starter, 1-7/8" exaust with a turbo muffler of unkown make. Otherwise stock.
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Sam Powell
Supercharged


Joined: 04 Jun 2006
Posts: 3952
Location: Gaithersburg MD

Post subject: (Sun Jul 18, 2010 11:30 am) Reply with quote

I tried to help you Matt, but the manual I have for the '69 simply does not give a value for the fusible link. However, for what it it worth, if you add up the values of the fuses in the main fuse panel, they come to just a little under 70 amps. I have upgraded my system to 120 amps by running parallel circuits and fusing each with a 60 amp circuit. I used number 12 wire in mine, while the stock fusible link is specified as #16 in the manual.

What I would suggest you do at this point is go on line and find a chart of amperage ratings for various sizes of wiring at 12 volts and for the length in question here, which is only about 6 feet at the most, and see what the rating is for #16 wire. That would likely be the rating of the fusible link that you would want to look for. You are looking for the fusible link that wil blow before the current on the wire exceeds its safe limit. This is a serious concern. Do not be tempted to wire past it. I have seen cars burn to the ground when guys just clipped it out, and soldered it back together. The problem there is that kind of mentality is also the type that will make another serious mistake which then leads to the need for a fusible link.

The information you are looking for is not here http://www.moparfins.com/Repairs/How_to_Fix.htm

but there is good info anyway for Mopar guys.

Sam



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wjajr
Supercharged


Joined: 16 Feb 2008
Posts: 4266
Location: Downeast Maine

Post subject: (Sun Jul 18, 2010 2:25 pm) Reply with quote

Dartman,

Sam is correct, there is no listing, or rating in the 67 FSM covering fusible links. I recall reading somewhere, or talking with one of the electrical venders, perhaps Evens Wiring, regarding this very question, and I recall the rule of thumb is to drop down four wire sizes from the conductor needing protection from over current. This may or may not be correct.

My 67 calls for a # 10 gage wire feeding the amp gage. At the engine side if the bulkhead connector that #10 steps down to a # 14 fusible link, passes through the bulkhead connector to a #10 gage conductor and on to the amp gage. I purchased my fusible link form Napaís help end cap.

My car is a convertible, and has an additional 30 amp circuit breaker to protect the topís hydraulic pump that other models donít have. So far this #14 link has served well. I donít have any additional electrical load from high output sound systems, so its electrical system is stock.

One must not use the same type of wire that is used to wire our cars to fabricate a fusible link. Special wire, coated in a special flame resistant insulation, with a prescribed length has to be used for a fusible link. It is designed to be safely sacrificed during an over current condition. Using a substitute wire could cause a fire, and allow too much time to pass before it melted, braking the circuit, resulting in damage to other sections of wire & devices down line from the link.

Another way to protect the main feed is to use a fuse. Just what size fuse to use is hard to calculate on these old cars. You donít want something that when it sees a current spike instantly blows, but on the other hand you donít want a fuse over sized, and too slow to react. That is why Chrysler and other auto companies used fusible links back in the day. They are slower to react to spikes, but will react to a continuous over current condition, and are cheaper than fuses. Crude, but effective.

Another safety device I employ on my old iron, is a battery shut-off switch. I use a cheap green knob device that Wal-Mart sells for about 8 bucks. It attaches to the negative battery terminal, and the grounding conductor going to the block. With a flick of the wrist all electrical current can be stopped if the need arises without the use of tools, which could save your car from the fire godsÖ

Bill



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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

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Aggressive Ted
Supercharged


Joined: 15 Jan 2007
Posts: 3775
Location: Black Diamond, WA

Post subject: (Tue Jul 20, 2010 12:39 pm) Reply with quote

The original alternators are about 40 amps and gauges max at 60 amps.....so it has to handle at least that much load.......hopefully not much more.

I know my Imperial with electric everything has several large 12 gauge fuseable links in parallel. It has 3 huge cables leading to the battery besides the large battery cable to the starter. Way bigger than my Dart........

One day the hood spring shorted through the huge wire bundle with the 3 "O" cables and shut the car down........my wife was cruising down the freeway at the time. They had to bring a huge diesel semi to tow the car home. It looked like some one did some arc welding under the hood.....each "O" wire had it's own 12 gauge fuseable link which had melted in half.

I replaced the (3) fuseable link wires and installed a 100 amp circuit breaker on the Imperial to be on the safe side and moved the wire bundle away from the massive hood spring.



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74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG
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