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?
NOTE: You "may" find your high-beam indicator light will not be as bright as it was. This is a small trade-off for the benefits. It can
be corrected through the use of diodes and a resistor however, we believe the diodes and resistor add unnecessary complication and
risk. Keep in mind the high-beam indicator does still work, it is just may be dimmer. If you are concerned, please e-mail us with
We are offering the 4Runner Premium-Plus harness at $94.50 plus shipping. Keep in mind, these are not the "inexpensive" “yellow"
harness from China, theseare real PREMIUM harnesses made by me in Denver, Colorado. Check out the details:
Headlight Services Premium-Plus Harness (Ground Switched) (See photo below.)
NOT FOR VEHICLES WITH DRLs (Daytime Running Lights)
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
HEADLIGHT SERVICES - 4Runner Wiring
1995-2002 Toyota 4Runner Premium-Plus Harness
(NOT for DRL or factory fog lamp equiped vehicles)
Extra heavy 12AWG wire for bulbs and power (made in USA)
Dual power supply with two fuses (redundant power feed)
High quality Bosch/Tyco resistor relays
High temp “ceramic” bulb connectors
Home-run ground wires (no risky “local” grounding)
All wires crimped and soldered
Want brighter headlights in your 3rd Gen 4Runner?