Relay Capacitor Harness 101

Interface Solutions

Here at Race Sport Lighting we are commonly asked questions about interface solutions. What are they? Why do I need them? Well, we are going to be doing a five-part blog series breaking this topic down. Interface solutions are all about keeping the vehicle’s computer satisfied. Today’s vehicles are specifically programmed to interact with every aspect of the vehicle. Whether it be fuel and ignition timing or head lamp and tail lamp circuits.

What does this mean to you? Simple, when you remove and replace an item (like a bulb) and replace it with something that is not exactly the same, the vehicle will see this as a fault and respond with an error. The reason for this is that the replacement part is outside of the parameters the vehicle is programmed for. So to prevent error lights, flicker, or flashing. You have to use an interface part to compensate for the difference.

Relay Capacitor Harness

This post we will be discussing the Relay Capacitor Harness and when and why you need it. We will also check out proper wiring. This harness is used to retain Day Time Running Light (DRL) function when installing HID or LED headlight upgrades.

Like amplifiers, HID ballast and LED drivers require good solid power. Not providing this stable voltage could shorten the life expectancy and over all reliability of the component.

A relay capacitor harness is commonly used in applications when these issues are present:
• On vehicles with 6-11volts. The trigger input on this harness will handle the lower voltage and keep the relay open.

• On vehicles with pulsed voltage instead of a steady voltage. The trigger input on this harness will handle the pulsed voltage and keep the relay open.

Installing a Relay Harness

Be aware that one harness will do both left & right headlamps. When physically installing the harness please verify the polarity on the vehicle side. Failure to do so will impair correct operation and may damage the harness.

Please see this helpful diagram below for proper wiring of the harness:

Relay Capacitor Harness

Race Sport Lighting Part Number: RELAY-CAP