April 30th, 2004 : Headlight Relays
Before I added relays to my headlights, if I drove for any extended period of time with my high-beams on, I would trip my headlight fuse. Apparently, those long trips the 14-volts had to make from the battery, to the fuse box, to the headlights, was heating the fuse up; my headlights would black-out until the fuse cooled off and then they would come back on again -- a very disconcerting experience to say the least! After installing relays as outlined below, I'm happy to report, this problem no longer occurs.
As part of my Mad Electrical Improvements project, I decided to put relays into my headlight wiring scheme ... one relay for the high-beams and one for the low-beams. You can read Mark Hamilton's article about it HERE.
If this is your first time installing relays, the kit above is the way to go ... but once you have all the supplies and experience, you can buy Bosch relays for about $3.50 each (like I'm now doing) via Parts Express. I just phone my orders in:
1-800-338-0531 but if you'd rather, you can order from the web site:
It's a pretty simple matter to find the two wires that come from your fuse box and send power to your high-beams and low-beams. Once you locate those two wires in the engine compartment area, you just cut them:
1 - Cut the low-beam wire.
2 - Take the section that comes from the fuse box and connect that to the white wire (aka #86) on the relay for the low-beams.
3 - Take the other section that goes to the left headlight and connect that to the yellow wire (aka #87) on the relay for the low-beams.
4 - Cut the high-beam wire.
5 - Take the section that comes from the fuse box and connect that to the white wire (aka #86) on the relay for the high-beams.
6 - Take the other section that goes to the left headlight and connect that to the yellow wire (aka #87) on the relay for the high-beams.
7 - Take the two black wires, one from each relay, (aka #85) and ground them to the frame.
8 - Take the two red wires, one from each relay, (aka #30) and connect them to a steady power source. If you're providing power to your engine area with a terminal block as I have, you'll connect a fusible link to the end of each wire and then connect the fusible link to the terminal block (see schematic below).
Here's a photograph of my engine area ... you can see the fan relays I installed yesterday and the terminal blocks I installed a few days ago. You can see the full photo-diary of each by clicking the "Back to Alan's Ride" link below.
I still have to finish the above by putting split loom on the wires and cleaning things up a bit ... but otherwise, I'm finished with my Mad Electrical project. Let me tell you -- this was all very worthwhile! Feeding power to the engine area with two terminal blocks, supplying a full 14.2 volts ... feeding the alternator with an 8-gauge wire, setting up my ignition-to-alternator wire with a diode and running the regulator wire to the terminal block, made my engine perform better -- and my voltage gauge smiles like it's on a happy vacation! Then, wiring my electric fan with double relays and a fusible link (instead of a circuit breaker) made a huge difference; my voltage gauge doesn't show any reaction at all when the fan kicks in ... and, finally, putting these relays in for my headlights surprised me tonight when I was driving at night and saw how much brighter my headlights are!
If you've been thinking about doing all this, stop thinking about it and do it! I couldn't be happier with the results I'm seeing.
And ... while you're at it, if you still have old "light bulbs" for headlights, swap those puppies out for a pair of Halogen Headlamps and really light the road up!
THANK YOU, Mark Hamilton! MadElectrical.com
P.S. -- You may also be interested in checking these other electrical projects out:
Mad Electrical Improvements -- [Click Here]
Wiring An Electric Fan With Two Relays -- [Click Here]
Wiring Dome Light via Door Switches -- [Click Here]
Understanding Relays -- [Click Here]
About Fusible Links -- [Click Here]