Brighten Your Lights – Installing Headlight Relays

What? Everyone has seemed to hear of this but it continues to mystify many. This is a rather simple conversion with drastic results. Upgrading your Jeep’s headlight circuit is a rather straight forward process and can provide that much needed nighttime light without the addition of expensive driving lights or replacement headlights.

some information provided by Daniel Stern Lighting

Reality: Factory design kinda stinks – well mostly

The power for your headlights is provided through a long electrical path that includes your headlight switch and headlight dimmer switch. All of this wiring, contacts, corrosion, and connectors compound together to amount to a significant voltage loss. Headlight output is drastically diminished with the decrease in voltage.

Solution: More power to the bulbs…but how?

Shorter path to the lights from the battery, also, higher capacity wiring. Usually the wiring in a Jeep is 16 to 18 gauge. 12 – 14 gauge in this application usually is best. Also, a larger gauge short wire can carry more current than a same gauge longer wire. If you are wondering how we can have a shorter path to the lights but still be able to turn them on and off within the cab of the Jeep enter the relay. A relay is a remote switch. A standard relay is turned on by a small amount of current that actuates a magnetic switch and only draws minimal power. The other side of the magnetic switch is another switch that can carry a larger amount of current. In this case the Jeep’s headlight switch turns on the relay which in turn turns on the headlights.

Before I did this on my own Jeep the headlight switch used to get too hot to touch. It eventually failed. This was the point I looked into this upgrade and now the switch does not even get warm due to the small amount of current required by the relay.

Parts:

• Relays: (2) Use a set of quality relays, remember, these are powering your headlights. Usually if you are using them you NEED them.
• Protection: Protect the new circuit with a fuse. These new wires can carry a large amount of current and can cause a lot of bad things to happen quickly if the wrong thing touches a ground source. A useful power tap accessory is an excellent addition to a Jeep. Painless Wiring makes a nice weather proof fuse block.
• Wire: Use a minimum 14 gauge for the main power lead and a good ground. Some smaller wire may be used for smaller connections.
• New headlight plugs. Why not? You are going through the trouble…no sense in reusing your old corroded light plugs. These are available at most automotive stores.

Before you tackle this project make sure you do things neatly and properly. Your vehicle headlights are as important as brakes. Know what you are doing! This project involves soldering and vehicle electrical understanding.

wiring diagram courtesy of Daniel Stern Lighting

Installation

Disconnect the battery before starting.

Find the two circuits that go to the headlights. One high beam one low beam, these will become the relay triggers. Select a good location for the two relays. I chose the back side on the drivers of the grill, the factory CJ wires run right through this area and it seemed out of the way.

Run a minimum 14 gauge FUSE PROTECTED wire from the battery or positive side of the alternator to the relay. Run another 14 gauge wire to the relay area to serve as a good ground. Attach a grounding bolt to the grille area near the relays to serve as a good ground distribution point.

The relays usually follow the same standard in regard to their pin layout. You can either connect directly to the relays using the slide on connectors or purchase a relay socket to simplify the installation. I prefer the relay sockets (I didn’t use them – but I would if I do it again) and also prefer soldering the connections instead of using crimp-on connectors.

Relay Technical

Relay pin layouts
86 is the relay switching (control) circuit input.
85 is the relay switching (control) circuit output (ground)
30 is the power circuit input.
87 is the power circuit output.

Headlight socket pin layout
56a is the high beam feed.
56b is the low beam feed.
31 is ground

Electrical Connections

Following the above diagram…

Relays

• Attach the high beam circuit feed from the headlight switch to the 86 terminal on the high beam relay.
• Attach the low beam circuit feed from the headlight switch to the 86 terminal on the low beam relay.
• Attach the new high power feed wire to the 30 terminal on both relays.
• Attach the 85 terminals to the new ground source.

Lights – NOTE: It may be easier to remove the headlights and their bezels to work on the inside grille wires.

• Attach the 56a wires to the high beam relay.
• Attach the 56b wires to the low beam relay.
• Attach the 31 wires to the new ground source.

Finishing up

Verify all connections are correct and connect the battery. Test the headlight operation. Reassemble the headlights and clean up all the wires using wire ties and/or flexible wire molding. This project can be completed in an hour or two by someone experienced in Jeep wiring.

jeepfan.com 1978 CJ-5 Project