By now, most vintage Ford electrical systems have seen better days. As these old wizards of light, sound, and function approach the age of 40, their insulation has become old and brittle. Cuts and splices have taken a toll. Chafing and short circuits have, in some cases, left a smoldering pile of ashes. More and more creature comforts have placed an increasing strain on an old Ford's wiring. It's time for a new electrical system from Painless Wiring.
Painless Wiring has developed a Mustang/Falcon/Comet-specific wiring harness designed to thrust your vintage Ford ride into the 21st century. Not only does this wiring harness jibe with most of your Mustang's existing switches, lamps, and accessories, it also affords you power for just about anything you'd like to add. If you're interested in adding a powerful sound system, Painless can help. What about a climate control system? The Painless No. 20120 system is up to the job. Power windows? Bring it on.
We're going to visit JMC Motorsports in San Diego for our Painless Wiring system installation in a customer's '66 Mustang fastback. It is impossible for us to cover every detail here. However, we're going to cover the basics, looking over the shoulder of the very capable John Da Luz of JMC Motorsports.
Painless Performance Products...
Painless Performance Products introduces the No. 20120 wiring system for classic Mustangs, Falcons, and Comets. The kit consists of a main wiring loom (underdash), a firewall-to-headlamp harness (underhood), a taillight harness (from underdash to trunk area), and the instrument wiring loom. Most of this system has plugs that are compatible with your Mustang's switches, lamps, and accessories. The rest of it must be connected with crimped connectors and the like.
Begin by disconnecting the...
Begin by disconnecting the battery, then disconnecting the firewall plugs. Unplug the neutral safety switch (if equipped). Remove the wire loom retainers at the inner fenders and shock towers. Disconnect the engine gauge feed. Detach all of the underhood wiring from the firewall to the radiator support.
Remove the headlamp bezels...
Remove the headlamp bezels and headlamps on both sides. Disconnect the headlamp leads as shown.
Disconnect the parking-lamp...
Disconnect the parking-lamp leads.
Remove the main power lead...
Remove the main power lead between the firewall and battery.
Inside, the instrument panel...
Inside, the instrument panel is removed first. The headlamp switch, wiper switch, and ignition switch are disconnected. The wiper motor is unplugged, as is the stereo. Behind the dashboard is the main wiring loom, which means there is a lot to disconnect. Everything must be disconnected, including the taillamp wiring loom.
With the main wiring loom...
With the main wiring loom plugs removed at the firewall, we are ready to prepare the openings for the Painless main wiring loom. Painless provides a template that enables you to modify these openings for the new bulkhead plugs. John Da Luz lays the template over the firewall passage and grinds the opening for a perfect fit. There are two firewall passages--one midway across the firewall and another in the corner by the master cylinder.
As you can see, each firewall...
As you can see, each firewall passage needs massaging to make way for the Painless bulkhead connections.
The corner passage near the...
The corner passage near the master cylinder is identical to the passage mid-firewall. John has laid down the template and will modify this opening the same way.
Each of the Painless wiring...
Each of the Painless wiring looms must be wrapped and protected from chafing. John has chosen to wrap each loom with electrical tape. Flexible, plastic anti-chafe may also be used to protect the wiring. Never leave the wiring exposed.
The new Painless main wiring...
The new Painless main wiring loom is fed into the dashboard as shown. The bulkhead connector is fitted through the firewall. Then, the underhood wiring loom is connected to the main wiring loom at the firewall. The main wiring loom's connector clicks into place at the firewall. This becomes a secure connection.
The underdash main wiring...
The underdash main wiring loom is inspected, with destination points determined before the wiring is wrapped. Each connection is routed to a switch or accessory, just to get started. Once the main wiring loom is positioned, we determine how switches, accessories, and lighting are connected.
Like the bulkhead connector...
Like the bulkhead connector mid-firewall, the bulkhead connector in the left-hand corner of the firewall is inserted into the passage, then connected to the underhood wiring loom to the headlamps.
The firewall-to-headlamp wiring...
The firewall-to-headlamp wiring loom mandates important preparation. Rubber bulkhead grommets are installed to protect the wiring from chafing and short circuits. The wiring loom should be wrapped with electrical tape or channeled through plastic anti-chafe. On the left-hand side, wiring is routed into the fender into the headlamp door, which gets power to the head and parking lamps. On the right-hand side, same drill, with power for the head and parking lamps.
The new headlamp and parking...
The new headlamp and parking lamp plugs arrive at the headlamp door as shown.
We have to get power to the...
We have to get power to the taillamps, back-up lights, and fuel-tank sending unit. Painless provides the wiring loom necessary to get there. The old wiring loom is removed first, which isn't easy. Then, the new wiring loom is fed into the "A" pillar, down the rocker panel, past the fastback air-extractor area, to the trunk. For hardtops and convertibles, take extra care to keep this wiring away from the window mechanism. As always, wrap this wiring or route it through plastic anti-chafe.
We tie the taillamps to the...
We tie the taillamps to the harness with bullet connectors. You may have your own ideas on this one. Bullet or knife-blade connectors make installation easier.
John Da Luz weaves his own...
John Da Luz weaves his own magic by using Heat Shrink at the bullet connections. This gives connections a professional look.
Switches each have a different...
Switches each have a different means of connection. Ideally, you will use the factory plugs at each switch. We were able to use the factory plugs in most locations. We discourage separate knife-blade connectors at each terminal. Gang plugs are more convenient--and safer.
The ignition switch, for example,...
The ignition switch, for example, has a factory gang plug. When you tie this gang plug to the Painless harness, you may use butt connectors.
However, we suggest soldering...
However, we suggest soldering these connections for safety and security.
The turn-signal switch is...
The turn-signal switch is connected using the factory gang plug.
Your main wiring loom installation should look something like this. It must all be wrapped, neat and orderly. It should also be anchored with zip ties or the like.
The Painless fuse box is the same size as the original factory fuse box. However, it holds 12 fuses and supports a greater load. Position this guy where the factory fuse box was. You may also locate the Painless fuse box anywhere you'd like.
The horn sounding system uses a relay in the Painless wiring harness. This is like the '64 1/2 Mustang electrical system. From '65 and up, horns are sounded directly through the horn switch. A relay takes the load off your horn switch. There is also a 10-amp fuse to protect the horn circuit.
Big-Time Protection The Painless No. 20120 wiring system offers you the protection of 12 fuses at the main fuse box, not including fuse protection elsewhere in the system. This fuse box is the same size as the original factory box for Mustang, Falcon, and Comet, with a greater number of circuits and fuses.
What's It Cost?
Chassis Harness, PN 20120: $589.99 (street)
What's It Fit?
'65-'66 Mustang '64-'65 Falcon/Comet