Diode Dynamics Heavy-Duty HID Relay Harness

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Relay harness for any HID setup.
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Waterproof Relay Module

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  • Heavy-Duty HID Relay Harness
  • Waterproof Relay Module
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The brand new Heavy-Duty HID Relay will power your HIDs directly from the battery, instead of the factory wiring. This relay has been designed from scratch, and utilizes a fully-sealed, waterproof relay, with flyback diode, and even has a built-in capacitor for input power smoothing. All wires are sleeved with braided techflex for an attractive appearance and extra protection. The input wires are each a meter long, and the output wires are one meter and two meters, which means the wiring will be long enough for even the biggest vehicles. The single-ground design makes installation easy. This relay was designed with reliability, convenience, and long-life in mind.

Your order Includes:

One Waterproof Relay Harness

A Full One-Year Warranty

  1. 2015 Ram 1500 with Projectors HID Relay Harness Review by Mark

    I had a lot of issues with my passenger HID headlight randomly not coming on due to CANBUS reasons. After troubleshooting this with DD and getting my truck reflashed at the dealer to try to get more volts to the headlight, all options were exhausted. This harness completely eliminated the issue. The only issue now is that my truck thinks my passenger headlight is always out, but DD warned me that this would happen. I decided I'd rather have a headlight than worry about getting the "headlight out" warning. I have no regrets. (Posted on 5/8/17)

  2. Great quality product Review by Nathan

    I got some cheap HIDs from eBay and they kept flickering off. This went on for about a year before someone told me I needed this product. I couldn't be happier, my headlight work great now. (Posted on 1/7/17)

  3. Good quality Review by Hussain AlSaihati

    Good quality and a little bit expensive
    I'm happy with this item (Posted on 10/14/16)

  4. Best purchase I've ever made. Review by Alex

    WARNING: This is a long review.

    So, it all started with a set of 6k HID's from a different company that was pretty well reviewed. Got them, installed them, but noticed that the colour had a very slight green hue to it, but was otherwise bright. Few weeks later, encountered some issues with one light not turning on randomly. This didn't happen often enough for me to dig into it, but it was often enough to be an annoyance. I simply ignored it for a while, hoping that it would go away on its own. Sadly, it didn't.

    This lead to a bunch of research which eventually pointed to a power harness. After spending a big chunk on the HID's, I figured that any harness would do, so I opted for the cheap eBay harness. Got it in the mail, installed it. Noticed that there wasn't much change in the hue. The light still had a flicker during startup, but the issue of having one HID not turn on randomly occurred less often (or so I thought).

    Fast forward a couple more weeks, and it started to occur more and more often. It was the winter at this point, and I was tired of driving in the snow with one light on. It got to the point where I had to start my car, get out to check if they were both on, and then continue on my drive. I found out that I could turn the HID's off for about 5 minutes, and flick them on and off and they would eventually both turn on. I googled and searched all I could with to no avail. Everyone simply pointed to a power harness (which I had installed). I figured it must just be the cold weather... Eventually, I got fed up, and decided to take a look at the connections and noticed that the relay on the harness turned all rusty and had some dried up white substance all over it (looked like battery acid). Quickly ordered what I thought was a decent power harness from the original website that I got the HID's from and installed them right away.

    Fast forward a couple of months. The one HID that always had issues turning on randomly (the passenger side low beam HID), still flickered when I started my car, but I figured it was normal. The colour seemed to have improved slightly but took a few minutes to turn to its bright cool white that I wanted. The issue of the passenger side HID not turning on still occurred, but was much less frequent. I was happy at this point.

    Fast forward to 2 weeks ago. The one light didn't work on start up, and wouldn't fix itself with the flicking on and off trick. Decided to drive at night and end up getting stopped for having a headlight out. That was it. I had to find a solution.

    I went on Diode Dynamics, ready to buy a whole new set of HID's and ballasts thinking I just had a lemon that stopped working once in a blue moon. Ended up running into this "heavy duty" harness. I figure, it'll be the last attempt before I decide to drop a bunch of cash on new HID's.

    Got the shipment quick. The quality of the product is miles ahead of the competition. Everything was wrapped well and looked extremely sturdy. But did it fix any of my issues?

    Installed the harness. First start up. The HID's turned on with a steady and strong beam of light. NOT A SINGLE FLICKER during engine crank. I couldn't believe it. I had been driving for almost a year with these HID's not running properly. I quickly got out of my car to take a look. There was zero green hue. The lights at start up were a nice crisp cool 6k white, and continued to focus and brighten as they warmed up. It was almost midnight, I decided to take the car for a spin to the darkest part of my neighbourhood. WOW. This power harness literally made the difference between "good" HID's, and properly fully functional super bright HID's.


    For anyone debating, "Should I buy the cheaper harness or this heavy duty one?" Do yourself a favour, and buy this heavy duty one. It's well worth the extra cost and really brings your HID's to its maximum potential and also potentially saves you a massive headache. (Posted on 7/14/16)

  5. HD Relay Harness Review by A martinez

    Much better quality and durability than the cheaper version, but also much too expensive. (Posted on 3/13/16)

  6. Worth the extra money Review by Jason

    Installed this wire kit on my 2015 Silverado. Install went smooth and have to say the kit is well built. The connections are high quality with everything heat shrink wrapped protected. Its a piece of mind having this installed on my new truck with its new HIDs. (Posted on 10/6/15)

  7. Quality harness. Review by Zachary

    I ordered this harness when I purchased an HID system for my 2014 GMC Sierra. This harness is listed as optional but anyone thinking about upgrading to HID's should really consider this a mandatory item. It allows the ballasts to run at full battery voltage as they were designed and can prevent a lot of headache for anyone who is not competent in troubleshooting automotive electrical systems. The B+ supply to the ballasts is also of a heavier gauge wire than the factory headlight wiring. The harness is extremely well built with quality wire and terminals that are well put together with weather pack connectors. All the connections are pre-terminated and the entire harness is protected with techflex adding to its quality appearance and providing a slight addition to abrasion protection. (Posted on 7/18/15)

  8. Fantastic! Review by StarKiller

    This harness was easy to install, it's high quality, something you won't get elsewhere. DiodeDynamics knows what they are doing, that is why I keep coming back to them for all my automotive lighting needs! (Posted on 3/26/15)

  9. Great Product Review by 417FahrenheitGTi

    This is heavy duty like described and super simple to hook up. Took me about 5 minutes to run it and hook it up. Wish all cars wiring on stock fogs was as good as this. (Posted on 11/30/14)

  10. Built Nicely Review by Raiel

    I like this a lot. It has longer wire and durable components. (Posted on 11/13/14)

  11. Heavy Duty Review by GENCPE

    Worth the extra money. This was long enough to reach the other side with extra room. Nicely built quality relay. Diode Dynamics has only the best quality. (Posted on 10/7/14)

  12. A definite must have Review by Adam

    I upgraded my wiring harness as accidentally my previous one got chewed up by my radiator fan which was my mistake. The quality of this kit is great, and it's so much superior than the stock harness. This is great to always know that water won't ever let your ballast lose power! Glad I upgraded. (Posted on 7/28/14)

Worry-free warranty

  • -Full 3-year warranty on all products
  • -No waiting: we usually send new items out with a return label (US customers only)


You will get quick help from our trained staff for any issues.

All Stage Series products carry a limited 8-year warranty.

For further details, please see our full article.

Domestic (US) Customers

  • - Same-day shipping for all orders placed by 12:00 PM CST (or until 4 PM with rush processing)
  • - USPS, for delivery in 3-5 days (on average)
  • - Express services are available, see exact pricing at checkout
  • - Fully Insured


International Customers

  • - We ship to all countries via standard mail
  • - Usually around $10 for LEDs, or $25 for HIDs.
  • - Choose your service on checkout to see exact prices:
  • - USPS 1st Class: 2-5 weeks
  • - USPS Priority: 1-2 weeks
  • - Express EMS: 1 week
  • - Please email us if you are unsure about shipping to your country.

You will receive updates from our site when your order is shipped, along with a unique shipment number to ensure that your order is correctly accounted for. This allows you to easily reply to us if you have any concerns.

Whether your order is big or small, it is tested through many run cycles, and each bulb is tested before shipment. Every single bulb. Every time. And if anything does go wrong, you can rely on our industry-leading warranty for worry-free replacement.

If you're not happy with your items, we want to make it right. So we have some pretty awesome return policies:


30 day return policy. All customers have 30 days from the date of original order shipment to return items.

Full refund, no fees. At Diode Dynamics, we offer free returns. That means no restocking fees, no administrative fees, and no hassle!

 Free return label. If your original order was over $50, you get a free return label for your items (US customers only). If your order was less than $50 or international, you can send the items back through your preferred method.


Within 30 days: If your original order was over $50, you can get new items shipped to you with a return label (US customers only). If your order was less than $50 or international, we can send you the new items first, but you are responsible for returning the old items.

Within 90 days: Any item can be returned for exchange or store credit within 90 days. The buyer is responsible for the cost of the return shipping, and must first return the old items. We'll still cover the postage for the new items.


Please note: due to the nature of custom acrylic pieces, we cannot offer any refund or exchange for returned custom acrylic items.


To make a return or exchange, please request an RMA, or give us a call. When we get it back, you will be notified and credited appropriately.

Again, all returns must be approved, with an RMA. This is so that we can process your return as quickly as possible when we get it. If you would like to return an item, please Request an RMA. Please include as much information as possible about the reason for return.

Alternatively, you can also send us a message, or give us a call!