Saturday, October 3, 2020

Repair C3 Corvette Fusible Link (Car Won't Start)

Above: The Vette looks good, even while
waiting for the tow truck.
As I was approaching home in my Corvette a few days ago, I decided to take "the long way home" at the very last minute, as I'm sure you've done many times.

Little did I know that that feller Murphy had plans of his own.

I was about a half a mile from my house when my Vette suddenly died. Fortunately, it had enough momentum and I was able to safely coast off the main road.

Nevertheless, the car was as dead as a doornail due to a complete loss of power.

I popped the hood and wiggled a few wires hoping that the ignition wire on the distributor had worked itself loose, but everything looked okay.

However, for a split second my hopes went up when I got back in the car and the courtesy lights were on and the buzzer worked when I inserted the key in the ignition. However, the moment I turned the key to start the car, it completely lost power again.

So I called for a tow truck.

While I waited, I was pleasantly surprised by how many motorists stopped to ask if I was okay and if they could help. Even a guy with a beautiful C6 Z06 stopped and offered me a ride home. As tempting as the offer was, there was no way I was going to leave my Stingray alone.


The tow truck eventually arrived and we took my dead car home.

While I waited for the wrecker, I thought about the reasons why the car would suddenly die like it did. And even though I know a car will keep running with a bad alternator, I thought I'd start there and have it checked.

So off came the alternator and battery when my Vette was back in the garage.


The guy at AutoZone ran a test on the battery, which came back as ok, but the alternator was bad according to the testing equipment. And from the noise it made, I think the bearing was on its way out.

Luckily, it was under warranty so they handed me a new one, which was great after having spent $109 for the towing earlier the same morning.

However, a new alternator did not solve the issue.

So I started poking around under the hood to see if the wiring and connectors looked okay. And this led me from the alternator back to the fuse block where I spotted a disconnected fusible link along with one of the alternator wires, the one that connects to the battery (BAT) post. In turn, the fusible link connects to the fuse panel thus powering it.


The picture above clearly shows the alternator 10-gauge wire next to the fusible link which, due to age and especially corrosion, decided to part ways at an inappropriate moment so close to home.

Yes, I played that scene in my head plenty while I waited for the tow truck. Had I driven straight home, the car would've probably died in my driveway or even in the garage, saving me both money and aggravation. Oh well.

As you probably know, there's not a lot of room under the hood of a C3 Corvette, and this wire—along with the fusible link—is part of the headlight harness, which places it between the brake booster and the windshield washer tank, ending on the firewall-side of the fuse panel.

Above: The photo shows the location of the wire and fusible link.
The picture was taken after repairs were completed.

From looking at the overall condition of the faulty wiring, it was obvious that someone had made questionable repairs at some point. But the first order of business was to see if the car would start if the wires were connected.

I jury-rigged a connection, reinstalled the battery, and turned the key.

The Vette fired right up!


WHAT IS A FUSIBLE LINK?
An electrical fusible link is a type of electrical fuse that is constructed simply with a short piece of wire typically four American wire gauge sizes smaller than the wire that is being protected. For example, an AWG 16 fusible link might be used to protect AWG 12 wiring. [Wikipedia]
A fusible link is designed to fail while preventing a fire from starting in the event of a short or overload. However, in my case, the fusible link connection had separated. In other words, the fusible link was ok.

Now, wiring repairs in such tight quarters are not easy, so I removed a few inches of the harness tape to expose more of the 10-gauge red wire, which would need to be cut anyway since the exposed end was unusable.

Luckily I had a piece of brand new 10-gauge wire at home.

By the way, wire gauges in the US are usually referred to as AWG or American Wire Gauge. The bigger the number, the thinner the wire. In other words, a 10-AWG wire will be thicker than a 14-AWG wire. Counterintuitive, I know. 

The gauge of the wire determines its Amp (Amperes) rating, or Ampacity if you want to get technical. A 10-gauge wire can handle 30 to 35 Amps (depending on temperature), while a 14-gauge wire can handle 15 to 20 Amps.

To connect the 10AWG original wire to the new piece, I fabricated a crimp from a connector and then soldered the wires to the best of my ability. Having a welding blanket to protect components near the area was great. I also used two layers of shrink tube to properly seal, weatherize, and strengthen the connection.

Since the location of the fusible link made it unreachable with the soldering iron, I used a solder seal connector that has built-in shrink tubing. And once it was installed, I used additional shrink tubing just to be safe.


In my case, I was lucky one of the fusible links ends broke, meaning that the fuse itself did not fail which is why my Corvette fired up the moment I temporarily reconnected the wires.

I consider myself fortunate this was the case. Otherwise, I would have had to disconnect part of the fuse panel in order to replace the fusible link itself, which would've been quite the task.

To make my repairs, as well as the wiring harness, look factory-fresh, I ordered a roll of automotive wiring harness tape. Vinyl electrical tape never looks "correct" once it gets gooey inside a hot engine bay with unpleasant results.


Previously, I had used a heat-resistant mesh to cover the old tired-looking harness, but never really cared for how it looked. And I had to use cable ties to secure it in place.


I also didn't care for the frayed ends. Some people melt them with a lighter then meld them together, but I don't particularly care for that approach.


The photo above shows the alternator wiring with the original tape, which is ready to be re-wrapped with fresh harness tape.


And this is the "after" shot of the same area. A lot cleaner and a definite improvement versus the plastic mesh and the old and tired original tape, even though the photos don't do it justice.


The picture above shows a close-up of the same area behind the alternator. I chose to wrap over the mesh cover of the coolant temperature sensor wire. I think it looks better that way.


The photo above clearly shows the difference between old and new. It is worth noting that factory harness tape is non-adhesive, while the cloth tape I used is. Only time will tell how well it performs inside the hot engine compartment.


I also rewrapped part of the harness where the fusible-link issue originated. However, I chose to leave the area I repaired free of tape, just in case.


Since I had plenty of cloth harness tape left, I also decided to clean up the exposed HVAC wiring harness.


Even though there's only so much you can do to wrap the wires, it looks much better, in my opinion.


The photo above shows the harness tape I used. Again, I have no clue as to how it will hold up long-term, but it looks a lot better than regular electrical tape which is NOT what you want to use in an engine bay, anyway.


And this is the new (remanned) alternator I got for all my trouble. At least I know it should be trouble-free for a few years.

Thank you for following my '76 Vette Blog!




3 comments:

  1. Came out good....only thing I was wondering is if the fusable link was bad, couldn't you just replace that "link" part and NOT have to go to the fuse panel? Reason I ask is, I am wondering if the wire just separated on its own or if the bad alternator had something to do with it. I just read somewhere that someone had a similar issue you had, but the alternator kept blowing the fuseable link because it was bad and after 3 blown fuesable links, he tested (bad) then replaced the alternator and all ended well as yours did.

    Anyways, looks great and glad she's back on the road! Electrical stuff in cars scares me the most when issues arise! Kind of a specialty almost when it comes to diagnosing and repairs.

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    1. Yes, but the thing is, I have no idea if the fusible link there was original to the car, and from what I could see, it went into the fuse panel. My first thought was to replace it just in case, but I chose the easier way out since it worked. There's hardly any room to work around the fuse panel without unplugging it and, frankly, I did not want to find out if the cure would be worse than the disease.

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    2. I would have done the same thing....if it started.....walk away and be glad! :)

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