73-87 Chevy _ GMC Trucks => Electrical => Topic started by: Lt.Del on July 16, 2007, 06:36:07 PM

Title: fusible link
Post by: Lt.Del on July 16, 2007, 06:36:07 PM
I think I may have a fusible link problem.
The other day, I drove my 383 stroker 79 big 10.  I noticed, as I parked the truck and revved the engine up, the Alt guage went well into the orange area, showing over 18 volts.  I let it idle, and the volts went down to normal.  Revved it up again, and she went way over into the orange area again. 

I shut her down and figured perhaps my voltage regulator may be in need of attention.   I didn't worry about it for a few days.  Went out to turn the truck on again today and it is as if the battery was dead, all the way dead...no buzzer, light, no radio, etc..

I put a guage on the batter, it shows 12.44 volts.  PUt a battery charger on it just to see something, and the guage shows she gets 18 volts w/ charger attached.  Turned the key on, still no buzzer, light, dome light, not even the headlights.  Dead!

So, I am wondering if i have a fusible link problem.  Anyone ever have a similar problem?

I need to figure out where to try to replace the fusible link. I understand that there may be four of them on my 79.

A) starter solenoid Batt terminal, 14 guange red wire

B) 16 guage at junction block

C) Battery feed to voltage regular #3 terminal (molded splice in circuit at junction block)

D) Ammeter circuit is protected by two 20 guage gusible links as molded splices in circuit at junciton block and battery to start circuit.

What? ???

Any one have pics or pointers?

Is this one?...


or this?....


Title: Re: fusible link
Post by: 123 pugsy on July 16, 2007, 07:28:13 PM
Those are both fusible links. Use your ohmmeter and stab the probe points into the wire on either side to check for continuity.
Title: Re: fusible link
Post by: Lt.Del on July 16, 2007, 08:06:25 PM
Guys, you will not believe this!

I was going to check various places to see where I get 12 volts in the circuits and I looked down below the battery.  The long positive cable that goes from the battery to the starter, where it routes over the frame near the tranny lines, was completely melted into two pieces!


I don't know why this didn't start a fire (well, it probably did and nothing else flammable around that area).  I guess the cable had a little copper showing through until finally it rubbed onto the negative grounded frame and completly burned into two.  Why the battery didn't blow, i don't know.  She still holds a great charge.

I guess my fusible links are just fine, it happened just about a foot and a half below the posi. battery terminal.

Perhaps all i need is another long posi cable to route back to my starter.

Boy that is scary.  My 2 1/2 yr old son was with me on my last trip with the truck the other day...and you can't get a kid out of those child-safety seats in a hurry.  :o

That would be the reason i have absolutely no volts at all anywhere on the truck. I guess this is the reason, on my last trip, the alt was putting out over 18 volts trying to compensate for the voltage loss.  I dunno ???


Title: Re: fusible link
Post by: 78rustbucket on July 16, 2007, 08:33:45 PM
wow, never seen that before. good thing nothing serious happened over it. im sure vehicles have burnt down because of a much smaller short.
Title: Re: fusible link
Post by: 75 C20 on July 16, 2007, 08:49:45 PM
  Why the battery didn't blow, i don't know.  She still holds a great charge.
hahah that reminds me of awhile bak when i 1st had my 79 i turn  a corner in town a lil fast and my battery was just sitting there decided to come out and short out on my inner fender- my truck stoped runing and smoke came out from under the hood- luckily i rolled down the block to the gas/service station where i work. i jumped it and the battery has held great chrage and hasnt given me trouble yet i had just bought that attery like a week before
Title: Re: fusible link
Post by: DnStClr on July 17, 2007, 01:22:42 AM
Andy. Was the starter connection loose? Might be the reason why the cable rubbed itself bare.
Title: Re: fusible link
Post by: 123 pugsy on July 17, 2007, 04:05:28 AM
I had that happen on an exhaust manifold before.It was no problem as there was nothing there to burn.
BTW it looks like it may have been vibrating against the star washer of the ground cable. Strap it to the frame tightly and you'll have no problems.
Title: Re: fusible link
Post by: VileZambonie on July 17, 2007, 10:06:46 AM
Happens all the time on these trucks when they are not held in by the brackets or when someone puts headers on and doesn't reroute. Luckily she didn't burn up.
Title: Re: fusible link
Post by: Lt.Del on July 17, 2007, 10:15:41 AM
I don't know if the starter cable is loose at the starter yet. Never had any problems starting.  Gonna take the cable off this weekend.

She must've been rubbing for a while.  I definately did my share of revving up that 383 stroker.  It would'nt take me too punch that gas quite often. Each time i did, i bet the motor rocked slightly--each time that happened, i bet the cable rubbed a little too.

Gonna go to the salvage yard and see if i can find the cable strap for the frame.  I have it attached correctly on two of the oil pan bolts, kind of running along the tranny lines to the starter.

Yes, i am lucky, could've started one heckofa fire and ended up like my brother's  expedition
http://www.delbridge.net/expedition (http://www.delbridge.net/expedition)

I hope some of you will learn from my little mishap, and i was lucky.  Check your cables frequently!!!  It gave absolutely no warning, except the last trip i made with it, the volts shot way up the guage. 


Title: Re: fusible link
Post by: Lt.Del on July 18, 2007, 08:22:23 PM
Well, I made it to the salvage yard today.  I saw an 86 blue suburban---wow, i hit the jackpot.  Since my  91 blue sub (http://www.delbridge.net/suburban) is blue and in need of a few parts, i retrieved a blue driver's door armrest, passenger side door blue pull strap and a few other misc. items.   Oh yeah, i forgot to mention my reason to go to the salvage yard...i was so excited to find my sub parts...my new positive battery cable for my  79 big 10 pickup truck (http://www.delbridge.net/chevy).  I pulled it from the same blue sub.  I even retrieved the bracket that holds the cable to the frame...where mine burned through....


I have a total of three brackets that hold the cable in its place.  I will always be mindful of the hot positive cable!

And all those parts for a grand total of $11.91.  Gotta love the salvage yards.
She runs like a champ yet again!!

Title: Re: fusible link
Post by: VileZambonie on July 18, 2007, 08:53:27 PM
Good! I usually run some convoluted tuning around my B+ cable too
Title: Re: fusible link
Post by: 123 pugsy on July 19, 2007, 04:38:03 AM
Nice clamp. I've never seen one like that. Every truck I've had,that clamp has always been long gone......
I think I'll take a look at mine tonight.
Title: Re: fusible link
Post by: Lt.Del on July 19, 2007, 05:06:59 PM
I made sure I have this cable secure now.  I like the plastic cable covering this one has that was on an 86 suburban. It is secure now from the frame bracket...


to up under the fuel pump...


to the clamp on the oil pan bolt....


to a secure tight connection on the solenoid...


Title: Re: fusible link
Post by: CruzinHigh on July 20, 2007, 08:18:04 PM
Whoa!  That's a close call for sure!  You're so lucky you didn't break down away from home from that one too.   ;)

You can never have too many clamps and retainers on a big hot wire like that.  Especially those of us who go off roading in our 4x4's should always make sure the wiring is secure.

Title: Re: fusible link
Post by: Mr79C10 on July 21, 2007, 05:36:54 AM
Good thread. Glad to hear that nothing caught on fire, that could of been ugly!
Question: on fusible links. Im wanting to replace mine at the starter but non of the auto parts store carrys them. Where else can I try or what can I replace them with?
Title: Re: fusible link
Post by: VileZambonie on July 21, 2007, 09:03:40 AM
All auto parts stores carry fusible link wire. It's sold in rolls by gauge. You need to match the gauge and length that is on your truck. Factory ones are wired up like a house. Every connection should be done inside a box in case of fire the box will run out of oxygen and the fire should go out. So if you look at your factory fusible links the connections are housed inside a plastic housing. Cut them off after the housing and solder in your new fusible link. Capping them is a good idea. Another option you have is to make a convenience center on the firewall. Route your cables there and use mounted Maxi fuses. A donor fuse panel could be a cheap way of doing it but the easiest way is to just replace the fusible link.

*here are some already made up links http://www.sherco-auto.com/electacc.htm
Title: Re: fusible link
Post by: Mr79C10 on July 23, 2007, 11:56:06 PM
Much Thanks!