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Headlight relay install with photos

8901 Views 6 Replies 5 Participants Last post by  dondavis
Just finished installing a headlight relay system on my 82 Spider. Thought my experience and photos might help someone else.
Bought the kit from Daniel Stern Lighting. Rounded up 12 gauge red and black wire for the power and grounds. Green 12 gauge for the high beams feed and blue 12 gauge for the low beam feed. Almost impossible to find small quantities of grey 12 and 14 gauge wire to keep the original color code. Also bought 14 gauge blue, green and black wire for the relay triggers. All the wire was in either 12 foot or 15 foot packages. Bought a pack of 7 ring terminals and pulled the insulation off of them - more about that later. Package of 10 foot of corrugated wire keeper and electrical tape was about it for supplies other than two sheet metal screws to mount the relay housings and a M6 bolt, nut and washers for the ground and some small zip ties.

I chose the drivers side front to mount the relay because it was close to the power and was next to the original routing of the headlight wiring. This location appears to keep all the wire runs fairly short. Of course before starting I removed the positive battery cable. Also had to remove the air intake system to give me access to this area.

For the power source I decided to use the power distribution terminal on the same side of the engine bay. To be able to fit the new wires on this terminal I needed to remove the insulation from the ring terminals. This junction is protected by a cover so the insulated terminals are not needed. There was just enough room to add the two wires needed to feed the relays. There were three original wire keeper tabs on the side of the bay that work perfectly to hold the wires in place as the wire is routed from the reays to the power terminal.

I really did not like the stock grounding configuration of the headlights. They simply put a small ring terminal under one of the headlight mounting screws. Used small gauge wire and the connection was marginal at best. In the photos you can see that I chose to drill a new hole next to the relay location and ground off the paint to make for a good ground. Used that for the main grounds from the headlights as well as the grounds for the relay triggers. This location also keeps the wire runs very short. The trigger grounds from terminals 85 on the relays went directly to this ground only inches away. (I ran a bit of extra wire to create a loop so the photo doesn't seem to show it coming directly from the relay). You can either drill the hole from the engine bay or from the inside of the headlight area. Another bonus is that you can reach both the nut and the bolt head when you tighten everything up. Downside is that you would have to remove the headlight if you ever want to retighten or add another ground to this location.

Wire routing to the headlights followed the original routing. The drivers side went from the relays directly into the access hole above them and the passenger side went in front of the radiator to the access hole. I ran both the high beam trigger and low beam trigger wires to the drivers side headlight to connect to the original headlight mounting socket using one of the connectors supplied in the kit. To keep things simple I used a very small screw driver to release the terminals from the original headlight connector so that I could remove the grommet and wires from the bucket. I then reattached the terminals (except for the ground) to the connector so that I could attach the kit connector to the original connector outside of the bucket. This retains the original wiring and connectors if for some reason someone would like it to go back to stock. I also had to buy two rubber grommets from the hardware store for the new wires to the buckets. In the engine bay I used electrical tape to make wire harnesses appearances to match existing wiring and used wire ties to attach it to the wiring in front of the radiator. Inside the headlight areas I used the corrugated split wire keeper to protect the wires from chaffing. I will post a couple of pictures of that area in a follow up post.


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additional photos

Here are a couple of other photos of the project


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Thank you, Steve. Very useful information!
I put my relays the same place, plus one more under for the front fog lights. I ran my power wires straight off the alternator. Good wright up, the factory should have done that in the beginning!
Steve, I too followed your lead and did the same exact install last week - huge benefits in headlight output! I used Daniel Stern's excellent services as well. Thanks for a perfect tutorial.

Next circuit in line for this treatment is the ignition.

I know the relays help save the light switch, but the lights are brighter now, too?

I nominate this thread for the Technical FAQ Digest.

David O'D
Irvine CA
I know the relays help save the light switch, but the lights are brighter now, too?
Oh, yeah. This illuminates (geddit?!) the reason relays are used, they pass more current than a switch. Think of it as a bigger pipe to items that draw a lot of current: headlights, starter motors, etc. Before, the headlights were trying to suck as much current as they could through the headlight switch, now, the switch just turns on the relays, and the relays do the heavy lifting.
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