Poundz9oh9 Posted May 18, 2007 Share Posted May 18, 2007 OK, I'm up to the headlights with my new wiring harness. I'm planning to do a 100/80w H4 upgrade to the headlight bulbs and I know that people have done the headlight relay mod to get more juice to the headlights by bypassing the old wiring connectors. Now my question is this. If I'm running a brand new harness, should I or do I NEED to do the relay solution as well? It's my understanding that it's the old wires in the Z that need the help for the headlights, BUT if I'm going with a new harness will it be necessary? TIA!! Quote Link to comment Share on other sites More sharing options...
jeromio Posted May 18, 2007 Share Posted May 18, 2007 Relays area always better than not. Especially for high draw apps like headlights. You want a heavy gauge wire and as little of it as possible between the lights and the battery. So right in between there you put a relay - one for high and one for low. Then you can run any kind of a tiny wire from relay to switch. There are plenty of good spots to mount the relay between the batt and lites - so it shouldn't really be much extra work. I have 5 relays all in a row on the inner fender by the rad support. Got the nice clip together mounts from waytek that use the nice Bosch relays (waytek sells those too). I have 2 for lites, 2 for fan and one for horn. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted May 18, 2007 Share Posted May 18, 2007 The stock system with all components and excess wire causes about a 3 volt drop to the headlights (about 9 volts). Upgrading to relays will provide a strong 12 to 14 volts to the lights and take load off those old switches and fuse block. It is one mod that I would always recommend. The difference in light output is nothing short of stunning. I always install load relays in every high current circuit of my cars/trucks. Quote Link to comment Share on other sites More sharing options...
Poundz9oh9 Posted May 18, 2007 Author Share Posted May 18, 2007 I understand that the stock wiring is garbage hence my installation of a NEW harness with NEW fuse box. My question was will the NEW wires be up to the challenge? Or should I do the relays just to make sure or will the NEW harness be enough? Thanks for the comments thus far though guys.! Quote Link to comment Share on other sites More sharing options...
DCZ Posted May 18, 2007 Share Posted May 18, 2007 The other advantage of using relays is that the switch on the steering column sees much lower current so you get better reliability there. That said, I have yet to do this mod on either of my Zs Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted May 18, 2007 Share Posted May 18, 2007 I understand that the stock wiring is garbage hence my installation of a NEW harness with NEW fuse box. My question was will the NEW wires be up to the challenge? Or should I do the relays just to make sure or will the NEW harness be enough? Thanks for the comments thus far though guys.! no matter what type of wiring you used, the DESIGN of the harness is definitely not ideal. the headlight relay upgrade is a GREAT investment. Dave (Zs-ondabrain) over at classiczcars.com makes an AWESOME headlight relay upgrade: http://classiczcars.com/forums/showthread.php?t=20365 Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted May 18, 2007 Share Posted May 18, 2007 The other advantage of using relays is that the switch on the steering column sees much lower current so you get better reliability there. That said, I have yet to do this mod on either of my Zs second that. Take the load off your old switch. Quote Link to comment Share on other sites More sharing options...
Poundz9oh9 Posted May 18, 2007 Author Share Posted May 18, 2007 Awesome, good points guys ..... relay mod it is!! Quote Link to comment Share on other sites More sharing options...
Daeron Posted May 19, 2007 Share Posted May 19, 2007 this is a relay write up that I made on my subaru forum; it came up because my ignition switch no longer could handle the current to actiate the solenoid on my subaru, but it has info in it for headlights as well. http://www.ultimatesubaru.org/forum/showthread.php?t=74632 There IS one error in it that I have yet to fix; the five prong relays I mentioned, I am wrong about the output of the 87a prong.. you would understand if you read the write-up, I am not going into it here. PM me if you like the write up, but want more info on my error; it will probably suffice to get me to just fix the mistake. Quote Link to comment Share on other sites More sharing options...
deja Posted May 23, 2007 Share Posted May 23, 2007 Its not so much the wiring as it is the combo switch. That switch will NOT handle the current those new lights require and will die a horrible death very quickly. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted May 23, 2007 Share Posted May 23, 2007 The power consumed (and hence light emitted) by the bulbs is proportional to the square of the voltage at the bulb. What that means for those who hated math in school is that if you increase the voltage across the bulb from say 11 volts to 14 volts, the power consumed (and hence light emitted) is increased by 62%. This is HUGE. Even if you ignore the benefits of taking the load off the switch and increasing its reliability, the increase in the light you can see on the road is worth it all by itself. Do the relays - you won't regret it. Quote Link to comment Share on other sites More sharing options...
spotfitz Posted May 23, 2007 Share Posted May 23, 2007 http://album.hybridz.org/data/500/medium/P10100321.JPG High beam, Low beam, turn signals and running lights. In that order. High res. available in my pics. As already mentioned, using the original wires to control the relay helps your existing wiring and combo switch tremendously. The higher output of the lights is a major benefit aswell. You can't go wrong with this upgrade, unless you wire it wrong. LOL Quote Link to comment Share on other sites More sharing options...
2003z Posted May 24, 2007 Share Posted May 24, 2007 another interesting part of the stock wiring is that when you run your hi beams, all the current goes through the high beam indicator in the dash. Thats reason enough for relays for me. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted May 24, 2007 Share Posted May 24, 2007 I did relays in my new harness that I made. One for regular beams and one for high beams. That way I can run both at the same time for night time mountain driving... I also ran an individual wire for each headlight (I have 4) In my sig you can see the dead wiring harness trying to power the main headlights and new wiring for the two under the hood. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted May 24, 2007 Share Posted May 24, 2007 I did relays in my new harness that I made. One for regular beams and one for high beams. That way I can run both at the same time for night time mountain driving... I wonder if running both filaments at the same time is going to shorten the life of your bulbs? That's a lot of heat to dissipate. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.