How To

Headlights for Your Classic

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by Miles Cook  More from Author

Brighter Headlights and New Wiring Are A Major Safety Upgrade

Headlight technology in the ’60s is nothing compared to what’s available today. Just like other automotive components such as tires, suspension, engines, transmissions and safety equipment, headlights have come leaps and bounds since the classic Ford cars we love were sold in the ’60s.

Speaking of safety equipment, headlights are among the most critical pieces of safety gear on any car. So, upgrading them is not only cool in terms of appearance and driving enjoyment, they’re the one thing that really needs to be on the money for nighttime driving. And the lights on older cars are almost always lacking when it comes time to try avoiding an accident.

Given that, we thought it would be a good idea touch on the subject of better headlights. But there’s more to it than just installing new headlights on an early car with electrical wiring that’s not designed to handle the power that modern halogen and Xenon headlights draw. And wiring is what this how-to mainly focuses on since actually swapping a headlight isn’t really a whole lot much more work than changing a household light bulb.

At one point we were wondering what sort of path to take on this subject until we came across a custom lighting kit that fits vintage Mustangs and other Ford cars such as a Falcon. Offered by Reenmachine, the package consists of a pair of Hella high-performance halogen H4 headlights and a modern high-output, relay-driven wiring harness.

The key to the whole system is the harness that essentially bypasses the car’s existing headlight wiring and employs the new wiring for a safe and effective upgrade of the whole arrangement. It’s a setup that looked really good and we’ve covered the installation here on a ’66 Mustang.




These days, seriously bright headlights are available for any car. The trouble with classic Fords is that the wiring in these older cars isn’t really designed to handle these high-wattage lights. Another problem is when using these high-output lights, the circuit breaker in the headlight switch will not handle the current. The cure for this problem is installing two relays, which are included in the wiring harness that comes with the Reenmachine package. The flat-faced Hella lights also look good as installed here in a ’66 Mustang.


The Reenmachine custom lighting system is pretty much a “plug-and-play” setup that can be installed in about an hour. It fits all Fords with two headlights. The included wiring harness is simply plugged into the car’s existing headlight harness via one of the old headlight plugs. From there, the harness is routed, connected to power and ground and the headlights are installed. Various “legs” of the harness are extra long to accommodate various mounting locations and routing. If there’s excessive leftover harness length, slack can be cut out and the wires can be securely respliced together (being careful to match the colors) or it can just be coiled up, zip-tied together and tucked out of sight. There’s plenty of room in the cavity behind the headlight buckets to hide the wires. Reenmachine also pre-installs the H4 halogen bulbs in the Hella headlight housings prior to shipping the systems out.


The lights themselves install just like changing a regular headlight. Begin by disconnecting the negative battery cable, then on ’65-’66 Mustangs, remove the headlight door. It’s held in place with four screws. Remove them and the door comes off to access the headlight retainer.


Loosen the three screws holding the formed sheetmetal headlight retainer. This should allow you to rotate the retainer (its holes are elongated) and remove it from the car. If you have the trouble, remove the screws altogether.


The old sealed-beam headlight should come right out and hang from the wiring. Unplug the old light from the wiring as shown and repeat for the other side. At this point, you should have both headlights removed with the ends of the old headlight harness hanging out of the holes in the headlight buckets.


Uncoil the new harness onto the floor and look it over. You’ll note it includes the two relays previously mentioned as well as a fuse, all of which are shown here. This is the main element of the harness. The rest of it is really just a male plug to connect it to the old harness in the car and two female plugs that connect to the new headlights.


Find a good mounting place for the relays and fuse. It’s unlikely you’ll need to access them later, but a suitable place for easy access is still a good idea. On this ’66 Mustang, we mounted the relays and fuse right outside from under the battery. Use the supplied self tapping screws to secure them in place as shown.


The completed installation of the relays and fuse in our subject car looks like this. Note the battery in the upper right corner of this photo.


The opening in this ’66 Mustang right above the battery was the perfect place to commence routing of the wiring harness. All three legs of the harness passed through here on the way to their required places. The two female plugs connect to each new bulb and the male plug connects to either one of the old headlight plugs. Run the harness so that each female plug comes through the hole in the back of each headlight bucket (where the old plugs came through) and so that the male plug is also in the vicinity of one of the old headlight plugs. For the cleanest routing of the harness, you’ll likely want to use the passenger-side old headlight plug nearby where the relays and fuse will also be. This is the one male plug already passed through to get to the old plug that came off the passenger-side headlight.


Once passed through, connect the one male plug to the old female headlight plug (in this case on the passenger side of the car). This is the secret to making this system work and negates having to do any rewiring in the car. When the new harness is plugged like this into the old one, it relegates the old harness to only having to deal with low currents passing through the old wiring and headlight switch. The current now going through the old wiring is only controlling the relays which, along with the new wiring, now handle the high current of the high-powered headlights. The unused old headlight plug is then tucked away back behind the headlight bucket.


The passenger-side female headlight plug is passed through the same hole in the inner fender above the battery…


…then pulled through to the headlight bucket and attached to one of the new Hella lights.


Once plugged in, the Hella light is reinstalled just like any regular headlight. Simply reverse the removal of the old light shown in steps 1-3.


With passenger-side light, relays and preliminary harness routing completed, we next moved on to the driver-side. This includes routing the driver-side connector underneath the radiator. We were able to get this leg of the harness inside the core support, run it underneath the radiator and then have it come out of this opening right next to the driver-side of the radiator.


Just like on the passenger-side, there’s an opening on the driver-side inner fender to run the female connector through the opening and to the headlight bucket.


Once threaded through, the female connector is plugged into the other new Hella light which has already been done here. Once the light is plugged in, thread the excess harness back behind the headlight bucket and into the fender as is being done here. The headlight is then installed and secured into place with same hardware as was used with the old lights and the headlight door is reinstalled.


Once the headlight is plugged in and installed and the excess wire is tucked into the fender, we went back and secured the underhood section of the harness with zip ties. Although the old headlight harness is no longer being used, it still serves a valuable purpose as a place to securely attach the new harness, as is being done here. Doing it this way really made for a clean routing job under the hood.


Here’s the new wiring harness zip-tied into place to the old headlight harness. This is the section of harness running from down near the driver-side of the radiator to the opening in the inner fenderwell.


With the headlights and harness installed, all that’s left is to connect the power (red) and ground (black) wires. Here an eyelet is attached to the red power wire. Attach another eyelet to the ground wire.


Connect the black wire to the negative battery terminal or other good ground. Be sure your ground connection is solid as electrical problems are often due to poor grounding.


Complete the installation by connecting the power wire to the positive battery terminal or the hot side of the starter solenoid as is being done here. Loosen and remove the nut on the solenoid, slip the eyelet onto the stud and reinstall the nut. Check over the whole wiring installation to make sure no wires are pinched, running over sharp edges or otherwise at risk for damage.


Four-Headlight Fords Too

The Reenmachine two-headlight package fits all years of vintage Mustangs (except for ’69s) and Falcons. For Mustangs, 1969 was the only year (vintage or late-model) that uses four smaller 5 ¾-inch lights instead of two 7-inch ones. Never fear, though, because if you have a ’69 Mustang or also some other four-headlight Ford car like a Galaxie, Fairlane or Torino, then you’re in luck. Reenmachine’s four-light system – that will also fit almost any classic car with four headlights – uses four Delta headlights (; a pair of low/high beams and a pair of highs. The included wiring harness installs very similarly to installing the harness in a two-light system. There are differences, though, such as that three old headlight plugs are retired rather than just one, but otherwise the wiring is basically the same. The Delta lights are also fantastic as hitting the high beams is like having full daylight right in front the car. This four-light system is also available from Reenmachine.





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