As scary as it looks, this...
As scary as it looks, this tangled mess of wires is really simple if you break it down.
There are few things that cause a classic car owner more frustration and dread than wiring and electrical issues. From starting and charging problems, to gauges and taillights that won't work correctly, tracking down wiring troubles can lead to endless hours of searching and to feelings of helplessness like nothing else.
The truth is that precomputer wiring harnesses are actually fairly simple systems. The reason most of us are so intimidated by them is because we have so little experience dealing with them. Of course, it doesn't help when a taillight problem could actually be located in a firewall bulkhead connector.
This rat's nest is the entire...
This rat's nest is the entire wiring harness. Once you untangle and stretch it out, it's not nearly as intimidating as it looks.
It's also true that most electrical troubles are not really electrical issues at all, but rather mechanical ones. Corrosion, vibration, and three or four decades of seasonal weather changes all work to undermine the physical integrity of the harness and its connections. Other problems can be caused by any number of dealer or previous owner additions that may not have been done correctly.
All the previously mentioned issues are certainly the case with the wiring harness in the '68 Barracuda that Muscle Car Restorations (MCR) is tackling as a testbed for their new program-the Progressive Restoration. This is a new consumer-available process where instead of restoring the car all at once, the car is done in stages, one section at a time. It's a great concept that enthusiasts can employ when they need to slowly restore their car over time, but still want to drive the car during the summer. It sounds like a great idea to us.
Notice the piggy-backed connectors...
Notice the piggy-backed connectors in the back of the fuse box. These could have been added by the factory during assembly or later by a dealer. Even aftermarket dealers could have made additions here. While this kind of addition is better than cutting and splicing wires, you have to make sure that the wattage-sum of all the accessories doesn't exceed the rating of the fuse on the other side.
Wiring harnesses are generally in three sections: under the dash, under the hood, and everything from the dash rearward. Many times, the wiring may be in good shape, and a rewrap is all that is needed. But what if your harness has been the victim of a guy with wire strippers, little blue snap-on wire clips, and/or three rolls of electrical tape? You might be better off simply replacing the wiring harness. You heard correctly, you can now get a completely new wire harness from YearOne. There is no way, however, to anticipate every option that could be on your car, so it's important to take a lot of detailed photos and careful notes during disassembly; that way when you begin to replace the wiring in your car you know for sure where everything goes. Keep in mind there could be some additional wiring that you may need to add to the YearOne harness. Do yourself a big favor and, if possible, remove the dash so you can restore it and your wiring on a bench. The underdash wiring is not nearly so intimidating when it's out in the open on a bench where you can see everything clearly. Removing the dash is especially worth the effort if your gauges also need work.
Before you decide that you do need a new harness, there are a few things to look at. If your harness doesn't have these problems, you might be lucky enough to simply rewrap and move on. Just remember though, there may be hidden problems that could come back later to haunt you, so keep that in mind when deciding if you need a new harness or not.
Corrosion is probably the...
Corrosion is probably the number one troublemaker for any electrical system
It can show up anywhere, causing...
It can show up anywhere, causing intermittent connections, loss of ground
Even heat buildup to the point...
Even heat buildup to the point of melting the connectors.
The missing terminal in this...
The missing terminal in this connector is for the amp gauge. Corrosion in a high-current connection will generate enough heat to melt the connector and wiring. This damage-especially to the plug-cannot be repaired, and since there will normally be damage to the other half of the bulkhead connector as well, it's best to replace it.
Another common connector problem...
Another common connector problem is broken retaining clips on the bulkhead plugs. This is normally caused by someone trying to improperly remove the connector. Over time, missing clips can lead to a loose connection, which can lead to overheating, and then a melted connector, and then . . . well, you get it.
Wire insulation can get brittle...
Wire insulation can get brittle over time, particularly under the hood. If your harness is this brittle, it's a good reason to simply replace the entire harness.
Many wiring problems are caused...
Many wiring problems are caused by what other owners have added in the past.
MCR finds all kinds of junk...
MCR finds all kinds of junk on old harnesses. Wire nuts and crimp on splice connectors should never be used for any reason.
They may be a quick fix, but...
They may be a quick fix, but they also invite corrosion and eventually will fail.
Maybe there is a way to repair...
Maybe there is a way to repair a melted connector after all. Some "clever" owner drilled out the bad terminal slot, ran a heavy gauge wire through the hole, and wire nutted both ends. I guess you have to give him credit; it probably kept him on the road.
Sometimes there are problems...
Sometimes there are problems that are caused by people who should know better. The gold terminal that you see here is connected to the green wire coming out of the back of the connector. It was likely added by a dealer or other repair shop to power some accessory, probably air conditioning.The problem is a GM terminal was used. While it fits in the terminal slot, its design is different enough that it breaks the plastic around the terminal when the other connector is plugged into it. It works, but now it must be replaced.
Good dielectric grease is...
Good dielectric grease is an absolute must when reassembling wire connectors. It seals out moisture and will protect the connections for many years to come.
If your fuse box terminals...
If your fuse box terminals are corroded, they can be a pain in the butt to get clean while still in the box. You can either carefully take the terminals out from the back of the box, or you can lightly bead-blast the fuse terminals while in the fuse box to remove any corrosion if they are going to be reused.
The blue wire with the yellow...
The blue wire with the yellow end is the fusible link that protects the entire system from overload and fire. Normally, cars use a 10-gauge power lead and a fusible link that is four sizes smaller (14 gauge). This is a special wire that has insulation that allows oxygen in so the wire will burn when it gets hot. If you experience a bad fusible link, or you know it's bad, under no circumstances should you replace this link with a common wire. Use only another properly sized, fusible link.
If your existing harness is...
If your existing harness is beyond repair, or you don't even have one, all you need to do is make a phone call.
Made specifically for each...
Made specifically for each car, the YearOne harness is simply "plug and play."
The connectors come pregreased,...
The connectors come pregreased, so they are literally ready to install. Notice the open slots. Often, depending on the application, this will be the case, which will allow you to add additional circuits that might be specific to your car.