fuseable link 72 LT1

[thomas cuhaj]

Don't laugh but while installing my new resto battery I accidentally shorted it out to the frame. I heard a small pop by the starter and caught a wiff of a fried wire. The car is completly dead, all fuses are ok, so is the battery.Is there a fuseable link in line that would cause these symptoms and where is it located?

thanks

[John H.]

Re: fuseable link 72 LT1

Yes, there's a fusible link at the starter, sounds like it did its job; if you look at the large (battery cable size) stud on the starter solenoid, you'll see a 12-ga. red wire connected to it. That red wire becomes a 14-ga. brown wire, which then becomes a 10-ga. red wire. The brown wire is the fusible link, which is now fried - it will be obvious from the blackened/wrinkled insulation that it has melted. I don't recall how long it is, but most good auto parts stores have replacement GM fusible link wires - you need a 14-ga. fusible link wire.

[thomas cuhaj]

Re: fuseable link 72 LT1

thanks John, I'll head out to the garage and tate a look

[Gary S.]

Re: fuseable link 72 LT1

Isn't there another fusible link going to the coil + terminal that drops the voltage down after the car is started? Not knowing much about electrics, could this be fried too?
Gary
72 LT1

[Jim T.]

Re: fuseable link 72 LT1

Gary if the 72 wiring is like my 68 and 70, and what is in my 71 Corvette service manual, the wiring going to the + terminal of the coil is a resister wire from the fuse block to the coil which reduces the voltage. This is why if you put a ZZ crate engine in these cars using the HEI distributor you have to run another wire to supply full 12 volts to the HEI and not use the factory ignition resister wire to the coil.

[Jack H.]

Yes & No....

The main fuseable link from early Sharkdom acted to protect the entire wiring system. When she popped (gotta peel back the harness tape of the branch serving the starter motor/solenoid) to find the puppy dog), the entire electrical system vis a vie the ignition switch went dead.

The dual wire 'thingy' you're talking about is the use of discrete wiring harness runs to eliminate the ballast resistor. Instead of having a discrete ballast resistor mounted to the firewall or ignition coil (different car lines put the ballast in different places), designers found they could 'embed' the function of the ballast resistor by making separate runs inside the engine wiring harness. By changing wire gauge (up/down) along a given run, the ohmic contact introduced by 'splicing' or by using controlled lengths of higher resistance wire (like aluminum vs. copper) created a 'distributed' ballast resistor.

This essentially eliminated a discrete part (ye olde ballast resistor) but kept the electrical function of the ballast intact (one voltage to the coil during start/crank and a lower voltage in run mode). In fact, this is exactly how the TI ignition system introduced to Corvette in 1964 works.

There is no discrete ballast resistor. There's an add-in TI wiring harness that's long (to the rad core support mounted TI amp) and contains a run of aluminum wire to serve as the 'run' lead.

So, 'could' the inadvertant short have burned up the ignition wiring? Well, conditionally yes. But, the car would have to have been in start or run mode and even then, the fuseable link's open circuit action would have generated a 'race' condition (who burns up first?) with the advantage going to the fuseable link, by intentional design....

[Gary S.]

Re: fuseable link 72 LT1

Jim, I believe you are absolutely correct on that. I cofused the fuseable link and resistor wire. Sorry to all for any confusion. As Roseanne Roseanna Danna used to say "never mind".
Gary