Before you do anything.... Check your voltage drop! If you are loosing a volt or more you are better spending your money on a new headlamp harness before you buy those fancy new bulbs. Actually with a new harness you will get the real benefits from those high-tech bulbs without the risk of damaging your factory headlamp wiring and switch.

If your car is a little older and you want to improve the forward lighting check your voltages before you spend a dime. I did extensive testing of my wife's 1998 Toyota 4Runner and was shocked. She was loosing up to 1.58 volts at her high beam and up to 1.33 volts on her low beam. We installed a new harness and reduced the maximum voltage loss on high beam to 0.42 volts and low beam to 0.29 volts.
The harness provided a 31-35% improvement in light (lumen) output. See my wifes data here and another 4runner we tested here. And here is a Tacoma.

The voltage difference (before harness and after harness) may not seem like a lot but light output is proportional to the 3.4 power of the voltage, so (13.47/12.32)^3.4 is about 35% more light, for the same bulb!. Pretty good for $72.50 or $84.50 and an hour to install! (And you can now run higher watt bulbs if you wish. See our bulbs for a full selection.)

It is important to do these tests under load (lights on, bulbs lit), engine running and compare the voltage across the headlight connector vs. the battery voltage. (CAUTION: You are working with your vehicle's lighting system. If you are not comfortable with this testing, ask for help from someone familiar with these tests. If you are in the Denver, Colorado metro area we can test your 4Runner with our custom made tester and we can install the harness as well, just drop us an e-mail. Please inquire about other vehicles.) Most sources say that if your headlight voltage is within 1 volt of the battery, you're fine. More than a 1 volt drop, you should install a harness. If you are going to run higher than stock wattage bulbs, install a harness whatever your voltage drop might be.

The human eyes are not terribly sensitive to small increases in light output. For example, it is probably hard to detect a 20% light increase. The increased light output you will see is often in the form of a more uniform light pattern (that is the dimmer areas are now closer in brightness to the brighter areas) rather than the bright areas being brighter. The result is more usable light pattern (more light on the road) for driving, which after all is the whole point of the headlights. We increased the output of my wife's 4Runner headlamps by over 30%. Wouldn’t you rather drive a vehicle with a 30% increase in light than one without?

No cutting of any wires required. This new harness if fully reversible should you want to remove it at any time in the future. The factory switch will now control relays that require little power of the original factory wires saving your precious factory switch gear and undersized wire. The headlamp electrical requirements are now handled by new heavy gauge wire and modern relays and connectors. You will need to drill two small holes for the relay mounting screws. (Or you can find industrial double sided tape to mount the relays.)

Keep in mind, these are not the "inexpensive" “yellow" harness from China, these are real
PREMIUM harnesses made by me in Denver, Colorado.


HEADLIGHT SERVICES - 4Runner Wiring
1995-2002 Toyota 4Runner Premium-Plus Harness
Triple relay / Dual power circuit
(NOT for DRL equiped vehicles)
$88.50
Want brighter headlights in your 3rd Gen 4Runner?

** NEW DESIGN HARNESSES AND KITS NOW SHIPPING !!**
1995-2002 Toyota 4Runner Premium-Plus Harness
Resistor / Single power circuit
(NOT for DRL equiped vehicles)
$88.50
All harnesses include:
- Headlamp wire is heavy 12 AWG (made in US)
- All wires sheathed in high-temp black tubing (made in US)
- Home-run ground wires (no risky “local” grounding)
- Premium quality Tyco brand relays (NOT from China)
- Interconnecting relay bases (made in US)
- All connectors are professionally crimped and soldered
- High temp “ceramic” type bulb connectors
Toyota 4Runner Harness – Triple Relay/Dual Power Circuit
Actual wiring used as resistance to illuminate the instrument panel high-beam indicator similar to stock harness. Headlamps remain ground-switched as stock.

- Dual power circuit with two fuses (Left and Right)
- Home-run ground wires (no risky “local” grounding)
- High beam indicator functions as factory
- Flash is high beam only
- No diodes or resistors
Toyota 4Runner Harness – Resistor/Single Power Circuit
A resistor is used to illuminate the instrument panel high-beam indicator. Headlamps remain ground-switched as stock.

- Single power circuit with one fuse
- Home-run ground wires (no risky “local” grounding)
- High beam indicator functions as factory only slightly dimmer
- Flash is high beam only
1995-2002 Toyota 4Runner Premium-Plus Harness KIT
Triple relay / Dual circuit (NOT for DRL equiped vehicles) $67.00
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3rd Gen 4Runner Wiring Harness Kits - Dual H4/9003 Headlamps
This kit includes all of the hard to find special components needed to make your own plug-and-play wiring harness in one simple purchase. The kit contains only the highest quality parts available. Wiring diagram included. Male H4/9003 plug included for use as a "trigger". No need to cut any factory wires. Wire not included. Kits are for Toyota ground-switched vehicles.
Toyota 4Runner Harness Kit– Triple Relay/Dual Power Circuit
Actual wiring used as resistance to illuminate the instrument panel high-beam indicator similar to stock harness. Headlamps remain ground-switched as stock.

-
Dual power circuit with two fuses (Left and Right)
- Home-run ground wires (no risky “local” grounding)
- High beam indicator functions as factory
- Flash is high beam only
- No diodes or resistors
Kit contents:
Female H4 "ceramic"type high-temp headlamp bulb connectors, 2 each
Male H4 connector, 1 each
Relay base, 3 each
Relay Tyco brand, 3 each
Relay clips 14-16 awg, 15 each
Relay clips 12-10 awg, 15 each
Ring terminal 5/16", 12-10 awg, 2 each
Ring terminal 1/4", 12-10 awg, 2 each
Ring terminal 3/8", 12-10 awg, 2 each
Fuse holder ATC, 12 awg, 30 amp max, 2 each
Fuse 20 amp ATC, 2 each
Mounting screws for relay base, 2 each
Cable ties, 8 each
NEW Premium-Plus Toyota 4Runner 3rd Gen Harnesses
NOT FOR VEHICLES WITH DRLs (Daytime Running Lights) OR FACTORY FOG LAMPS
We are now offering two harnesses for the 3rd gen (1998-2002) Toyota 4Runner. One is a triple-relay design and the other is a resistor design. We have debated and debated offering only one harness but I have decided to let you make the decision as to which harness will best fit your needs. Both are described below.