Author Topic: Fusible links  (Read 2388 times)

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Offline 87DodgeW150

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Fusible links
« on: September 7, 2007, 09:10:49 PM »
I've blown several fusible links in my 87 Dodge W150 P/U L.B. with 2 bbl., 318 and auto trans. When replacing the blown ones on previous occasions, I have noticed that the wires are not copper colored. I guess age has worn off that shiny newness. I am convinced that a new harness will solve alot of little problems, such as blinkers causing gauge to tick every time and  the ammeter never seeming to be correct. Could the deteriorating wiring harness be causing these things? Where do I find another harness for under the hood? Do I need to re-wire the inside of the truck as well?
I have read some of the threads here and would like to add my truck to the list of gutless, gas guzzling 318s. How tuff is it to rebuild a carb. Any special tools? Is there a how to here on 2bbl Holleys?
Post or e mail--- vambo213@yahoo.com
87 Dodge W 150, 318, 727, L Bed
Want inexpensive fixes to do myself, r. susp. sags, better intake, better exhaust, body lift, lift leaves all around, basics.

Offline ToxicDoc

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Re: Fusible links
« Reply #1 on: September 7, 2007, 09:22:19 PM »
Fusible links blow because of increase current or resistance generating heat.  Since you're blown "several", first thing I would check is the two main grounds.

 One is located on the driver's side firewall near the steering shaft if I remember right.  The other one is on the driver's side of the radiator support.  Each is held down by a single bolt/screw.  Clean off the surfaces carefully and apply dielectric grease to seal the contacts after you re-tighten.

If you find your harness is truly so bad it's beyond repair, you can look or post in the classifieds here or check salvage yard listings.

 lastly, unless the interior isn't working well, I'd leave that harness alone.  Being protected from the elements usually protects it.  Of course a previous owner or a radio installer sometimes screws that up too...
'85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

Offline 87DodgeW150

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Re: Fusible links
« Reply #2 on: September 7, 2007, 10:09:30 PM »
I was thinking about an after market harness. Are there any companies out there making them, web sites?
I will take your advice on the two main grounds and will invest in some di-electric grease. Do all auto parts houses sell di-electric grease? Would the discoloration on the wires cause enough resistance to increase the amps in these circuits?
87 Dodge W 150, 318, 727, L Bed
Want inexpensive fixes to do myself, r. susp. sags, better intake, better exhaust, body lift, lift leaves all around, basics.

Offline Chump

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Re: Fusible links
« Reply #3 on: September 8, 2007, 04:12:53 AM »
I was thinking about an after market harness. Are there any companies out there making them, web sites?
I will take your advice on the two main grounds and will invest in some di-electric grease. Do all auto parts houses sell di-electric grease? Would the discoloration on the wires cause enough resistance to increase the amps in these circuits?

If the discoloration you are seeing is kind of a gray color than the fusible link wire is probably tin coated copper which is designed to be more corrosion resistant. If it's blue in color than you have a high heat issue or what is known as thermal runaway. Here's a little info from some technical files about the conductor material...you will notice that many types are used but most common on automobiles is the tin plated copper stranded wire.


Quote
Fusible link wire is an overcurrent protection device for an electrical circuit that utilizes a conductor which is generally two to four AWG wire sizes smaller or has a higher relative resistance than the other conductors in the electrical circuit. Fusible link wires commonly comprise a central electrical conductor, such as stranded copper, tin-coated copper, brass, copper-nickel alloys or other similar metals, surrounded by a thermosetting electrical insulation typically made from chlorosulfonated polyethylene, having relatively good insulating properties and resistance to heat and the adverse chemical environment present in the vicinity of an automobile engine.
If you have no time to answer the questions or try the advice then don't expect to fix it anytime soon!


Offline DODGEBOYS

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Re: Fusible links
« Reply #4 on: September 8, 2007, 05:21:14 AM »
you have a dead short / first place to look is the floor mounted dimmer switch / also read thru the electrical F&Q section
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Offline 87DodgeW150

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Re: Fusible links
« Reply #5 on: September 8, 2007, 06:31:31 AM »
actually I smoked the one for the power windows the other day. Is it advisable to replace these f. links with regular fuses and what value fuse to use for each f. link?
87 Dodge W 150, 318, 727, L Bed
Want inexpensive fixes to do myself, r. susp. sags, better intake, better exhaust, body lift, lift leaves all around, basics.

Offline ToxicDoc

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Re: Fusible links
« Reply #6 on: September 8, 2007, 02:48:35 PM »
actually I smoked the one for the power windows the other day. Is it advisable to replace these f. links with regular fuses and what value fuse to use for each f. link?

Do not replace them with regular fuses.  Regular fuses don't have any "give".  A small surge will blow one.  Links can tolerate a momentary surge (like turning on the headlights, etc) without blowing.

Dean, since he mentioned "links" in plural, I don't think he's talking about a single circuit.
'85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

Offline DODGEBOYS

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Re: Fusible links
« Reply #7 on: September 8, 2007, 04:27:44 PM »
true there TOXIC dude / but its still a dead short / on the windows its probly the wiring between the cowl and the door / the wiring bents and cracks from opening the door so much / l,d look there to fix that / he does not mention which other systems blow out
put your truck info HERE
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Offline jungle

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Re: Fusible links
« Reply #8 on: September 8, 2007, 05:28:23 PM »
I blew one on my 85 RC. The wire that ran to the oil pressure sending unit grounded on the fire wall & blew the link. The truck was a year & a half old :'(.
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Offline fal308

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Re: Fusible links
« Reply #9 on: September 8, 2007, 06:38:31 PM »
You can also replace the links with an automotive circuit breaker. I used to belong to an RX-7 club and that was a very popular mod as the fusible links in the7s were for the retractable headlights and the main power line for the electrical system. Blow the link and you were stuck on the side of the road, whereas with a circuit breaker you just reset the breaker to get you home.
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Offline Chump

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Re: Fusible links
« Reply #10 on: September 8, 2007, 08:35:47 PM »
Ok...let's take a deep breath :)
We need to know what specific fusible link/s are blowing and does the same one blow all the time?

As far as the power window fusible link goes...power is supplied to cavity #2 on the fuse block and there should be a 30 amp circuit breaker plgged in there. If a problem exists in the window circuit after the circuit breaker the breaker is supposed to open and close...the fusble link should not blow. If the problem is before the circuit breaker as in the ignition switch or wiring than I could see the fusible link blowing and the problem has to be from the link to the fuse block before the circuit breaker.
If you have a tilt steering column you may have melted wires and/or a bad ignition switch on the steering column near the bottom. Also check fuse#1 30 amp(Blower motor) to make sure its the correct value as both fuse #1 and #2 slots are both fed from the ignition switch :):)
If you have no time to answer the questions or try the advice then don't expect to fix it anytime soon!


Offline 87DodgeW150

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Re: Fusible links
« Reply #11 on: September 20, 2007, 09:24:46 PM »
All very good suggestions and I will look into each one of them. I have checked the grounds and the one on the radiator I do recall sanding down the metal there and re-attaching the gr. wire. The other ground seems to go to the valve cover on the dr. side or to a bracket on that side. Naturally it is all oily and greasy. I have a little work to do on that one.
In the books I have on repairs, it lists colors of the various fus. links but no amp rating. If I was going to replace the fusible links with circuit breakers, what values would I use? What values are the different colors for these fusible links?
I have blown the F.L. for the windows twice now. Once was last year and then 2 weeks ago. The other ones were for the heater circuit, last year as well, and the first one was major. 2 years ago it wouldn't start, so that means the main one. I would love to have circuit breakers for these.
87 Dodge W 150, 318, 727, L Bed
Want inexpensive fixes to do myself, r. susp. sags, better intake, better exhaust, body lift, lift leaves all around, basics.

Offline Chump

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Re: Fusible links
« Reply #12 on: September 21, 2007, 10:53:54 AM »
•   Does fuse cavity #1 have a 30amp fuse installed? Check the slot where it fits for heat damage. check the fuse itself.

•   Does fuse cavity #2 have a 30amp circuit breaker installed? Check the slot where it fits for heat damage. check the circuit breaker also.

•   Do you have a tilt steering column? We need to know this because the wiring is slightly different for this option and the switch/wiring are known trouble areas.

The ammeter needle on this year does not move like the older pre 1981 trucks. This was a design change to eliminate fires in the dash boards.

The blower motor and the power windows are fed off the same fusible link.
If you have no time to answer the questions or try the advice then don't expect to fix it anytime soon!


Offline 87DodgeW150

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Re: Fusible links
« Reply #13 on: September 21, 2007, 06:39:50 PM »
I have 2 metal jacketed 30 amp fuses in my fuse box. No apparent damage to them or the sockets they are in. It starts and runs fine. After replacing the F.L. again, the windows work fine.
Yes I have a tilt column, PS, PB, PDL, PW, AC (that doesn't work), 3 sp. auto trans, intermittent wipers, and an aftermarket trailer brake setup.
87 Dodge W 150, 318, 727, L Bed
Want inexpensive fixes to do myself, r. susp. sags, better intake, better exhaust, body lift, lift leaves all around, basics.

Offline Chump

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Re: Fusible links
« Reply #14 on: September 22, 2007, 04:57:55 PM »
Well lets go into more detail.:) I'm 99.9% sure that your windows are not the cause of your blown fusible link and that the blower motor circuit(or A/C as you call it) is the culprit , along with your ignition switch and wiring. But you still need to check fuse cavity #1 for a 30 amp FUSE and check the socket it plugs in to. Diagram below.





« Last Edit: September 22, 2007, 05:12:32 PM by Chump »
If you have no time to answer the questions or try the advice then don't expect to fix it anytime soon!


Offline Chump

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Re: Fusible links
« Reply #15 on: September 22, 2007, 05:11:43 PM »
Oh yeah...this is what the connectors at the ignition switch can look like, the vehcle still ran but had intermittent problems. This came off a 77 New Yorker...the owner was too cheap to buy a new harness for $20 so he rigged it.

If you have no time to answer the questions or try the advice then don't expect to fix it anytime soon!


 

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