START HERE - Disconnect the battery

Remove the red/positive/+ lead from the battery. Do not attempt to proceed with any further work until the battery is disconnected.

If a large spark is seen when you disconnect the red/positive/+ lead from the battery - stop here. You have a short somewhere in your wiring that needs to be identified and fixed before proceeding.

Step 1: Removing the headlights

Remove the 3 screws from the headlight bezels and remove the bezels from the grill (my retaining clips had broken/come loose, pay attention to any falling clips - you might want to replace them with new screws. your experience may vary.). Next, remove the 3 small phillips head screws securing the headlights ring to the headlight buckets. You want the chrome ring, not the bucket to come off. NOTE: Do not remove any screws with springs as the springs are used to align your headlights, removing any screws with springs will cause the headlights to go out of alignment and causing dirty looks from oncoming drivers.

Step 2: Checking your existing headlight circuits

overview

We are going to use some existing wiring to help speed the installation up. We are going to use the circuit from the dimmer switch all the way to the headlight bulbs. But, we are going to read the circuit in 2 steps to make sure that the wires are in great shape before we use them, this will help isolate and resolve any problems that may exist. Use the resistance settings on your multi-meter to read between the connector block and the headlight plugs on both the right and the left headlight. Do them one at a time, i.e. read the connector block to the left plug. Once that reads correctly then read the connector block to the right plug. Do this for both the high beam and low beam circuits. Then we will read between the dimmer switch and the connector block

zero the meter

Move your meter to the lowest resistance setting (mine was labeled R x 1) and zero the meter. To zero the meter, connect the + and - leads together, find the adjustment wheel, and move the needle/display until it reads 0. The zero position in also known as the open position.

checking the headlight circuits

battery is still disconnected, right?

Starting with the left headlight plug, read pin 1 (hi beam) to connector block stud hi beam checking for zero/open. It should read open, if you get a closed reading you need to replace the wiring or the plug. Open means that there is a connection between the 2 points. If you are using an analog meter the needle should swing from the closed (or infinite resistance) side to the open side. If you are using a digital meter then it should read 0. Use the lowest resistance setting you can, but even at the highest setting the needle should move (analog meter) or the gauge should read 0 (digital). If you have problems here be sure to do a visual first before panicking. Is the wire cut somewhere as it comes thru the grill? Are the connectors corroded? Is the plug decayed? Try reading the connector from the back of the plug to make sure you have a good connection. Now, read pin 2 (lo beam) to connector block stud lo beam checking for zero/open. read pin 3 (ground) to a bare metal spot on the body somewhere. Resolve any issues before moving on.

Once all the readings are correct, move to the right headlight

checking the dimmer switch circuits

Now this one is a bit trickier, but only because they are pretty far away from each other. We are going to read from the output of the dimmer switch to the connector block. Pull the carpet back and disconnect the plug from the dimmer switch. Read the hi beam circuit - between the hi beam/right lug on the connector block and pin 1 on the dimmer connector checking for zero/open. Since your meter leads probably won't reach between these 2 spots use some additional wire on your leads to help reach the 2 spots. I made a small "extension cord" with about 8 ft of wire and an alligator clip on each end to help out on these types of distances. Read the lo beam circuit - between the lo beam/center lug on the connector block and pin 2 on the dimmer connector checking for zero/open. Resolve any issues before moving on.

checking the power feed

this will help us identify where we can patch in to the main power feed for the headlights. remove the headlight switch by first removing the knob from the switch. Reach under the dash and push the pin/button on the bottom of the headlight switch in as far as you can and then pull out on the switch. The knob and pin should come right out, but this can be tricky. Using a small flat blade screwdriver, spin the inner ring so that it loosens and the switch should come out. Ok, after looking at the pin identifiers on the switch, read between the H connector on the headlight plug and the power input on the dimmer switch checking for zero/open. I believe that the wire on my truck coming off the H connector was yellow, but as always with any jeep yours may be different. The switch has the letter H marked on the plastic, be sure to match that up with the correct wire on the plug when you read the circuit.

finished?

Resolve any incomplete circuits before moving on. If you can't figure out what the issue is that is causing the problem then replace the bad wires with new ones. Use #10 gauge wire as a replacement, and try to match wire colors on the wires that you are replacing to make troubleshooting easier later. To help you identify replaced wires, cut the connectors off each end and place a tie-wrap snugly around each end of the wire. Later on if you see a single wire with a tie-wrap on a wire you know it should be dead.

Remember, if you find any problems here you will have problems later once we try to fire the lights up later on. Once you get zero/open readings all the way thru move to step 3

Step 3: Cleaning your connectors

OK, the hard work is over. If you have made it this far, then you have seen all the wires that affect the headlights ability to put out light, and we know that they are good. This will help you troubleshoot any problems that come up later after we are done. Now on to the cleaning and mounting phases.

Use the 400 grit paper to clean your connections on the connection block. This will help ensure that any crud built up over the years will not cause the power to drop as it move towards the lights. Any power drop, no matter how slight, will significantly reduce the amount of light your headlights put out, our goal here is for minimal, if any, power loss.

Use a 3/8 wrench to remove the nuts ONE AT A TIME from the connectors being careful to put them in a safe spot where they will not be disturbed and you won't forget where they are. You have 5 things to clean using the sandpaper. 1) clean the stud/post till the crud is removed, don't sand it too far down and affect the threads. 2) Clean the bottom of the nut. 3) Find the 2 wires that route down to the grill and clean both of the round eye connectors. 4) Find the wire that comes from the passenger compartment and clean the round eye connector. 5) clean the washer. Put the nut back on and tighten it down.

Repeat for the other 2 posts. Even though there are only 2 connectors for the headlights, do all 3 this way - one at a time. The 3rd connector is for your parking lights in the front, cleaning the connectors for the parking lights may help make them brighter (it won't help for the blinker circuit, those are different wires)

Step 4: Install the new bulbs

Install those brand-spankin' new Sylvania XV bulbs into the plug. Install the retaining ring and screws. Install the bezel. Repeat for the other headlight

Step 5: Install the new dimmer switch

Remove the 2 large phillips screws holding the dimmer switch to the floorboards and install the new switch. Reattach the dimmer connector plug.

Step 6: Install the new fuse box

Find a spot on your inside firewall to install the new fuse box. I found that since I don't have a clutch, the spot on the firewall to the left of the brake pedal was a good spot. I would not recommend putting the fuse box in the engine compartment, getting water in fuse box could cause problems. Do not install the fuses yet, let's get it wired up first. Locate the power input for the fuse block and identify a power out circuit for the lights and another the switch.

Step 7: Install the new relay

I located my relay right above the fuse box, I also stuck a piece of rubber from a bicycle tube behind the relay to make sure that there would be no possibility of shorting the wires out to the body. Drill a hole in the firewall and thread the screw into the metal. You might want to leave the relay out until we go to hook it up, the connections can be hard to see.

Step 8: Wiring the wag

Coming down to the end of this, be sure to take your time here

main power feed

Ok, lets connect the wire directly from the battery to the fuse box - be sure to read all of this first before proceeding. Here's how to do it - Crimp the large round eye lug to the fused wire. Using a straight connector crimp, crimp the fused wire to the 10 gauge wire. Remember that we have not hooked the battery up yet. If you used the un-insulated lugs be sure to use your shrink wrap tubing here to cover the exposed connectors. Remove the nut on the positive battery connector and attach the large round eye connector to the bolt and finger tighten the bolt back down - do not connect the red/pos/+ terminal to the battery yet!. Note that this connector will be prone to corrosion so be sure to check it at least every time you check you oil, replace the lug as necessary. Carefully route the wire into the passenger compartment by using the hole directly above the ballast resistor on the firewall. It is in the middle of the firewall and has a pack of wires going thru a rubber grommet. Route the wire in a safe fashion (use your better judgement here!) to the fuse box, measure and cut the wire to length. Attach the correct connector for the fuse box and connect the 10 gauge wire to the power input on the fuse box. Secure the wire using tie-wraps both in the engine and passenger compartments.

a note on fuse boxes

Not all fuse boxes have "one power in to many circuit output" configurations - some are one power in to one circuit out. Be sure you understand how your fuse box is designed to be wired up before you go further. This doc assumes that you have one power circuit in and the fuse box provides multiple output circuits based on the presence of a fuse. If not, be sure that each fuse will have some power source.

switch power

Connect the 10 amp fuse into the fuse box socket that you identified earlier as the 10 amp line. Run a 10 gauge wire (this is overkill, but...) from the 10 amp fuse box output to the connector marked B1 on the headlight switch plug and disconnecting the wire that is currently in the B1 socket. You can splice the new wire onto the old or (preferred) you can remove the lug from the plug and crimp a new lug onto the plug. <set doctor seuss mode off>. My wire was red/white, yours may be different. Grab the old wire that was going into B1 and trace it back into the wiring harness as far as possible. Since this wire carries 12v we want to disconnect it. Once you have found the source, take a big breath and using your wire cutters clip the wire, now exhale. Remove wire, feel the empowerment, throw it into the air and onto the ground on the driveway, do the dance. If you were unable to snip the wire at the source, place a wire nut over the end of the exposed wire to be sure that it does not short out. You now have a huge power feed into the switch.

HOWEVER, do not stop here - these headlight switches are not designed to handle the power requirements of the new bulbs that you put in. You will smoke the switch and may light your cherished waggie on fire if you do not install the relay in the next step!

Essentially what you have done is installed large current sucking devices (headlights) that are still connected to the switch, and have fed the switch with a huge amount of possible power (30 amp line direct from the battery). The switch is the weak sister, it will attempt to pass in all the power as it overheats and starts to smoke and burn.

relay power

Connect the 30 amp fuse into the socket that you identified earlier as the 30 amp line. safely string a 10 gauge wire from the 30 amp fuse box output to the connector marked "30" on the relay using a spade lug on the relay end of the wire. This is you 30 amp power that will be delivered to the headlights when the relay is turned on. Put a spade lug on the end of a 10 gauge wire, and run it from relay connector "85" to ground, use the small round eye connector on the ground end. This provides a relay ground.

headlight power

last step!

ok, we now have power to both the relay and the switch, now we need to have the headlight switch activate the relay AND get the 30 amp power out of the relay and into the dimmer switch on its way to the headlights.

Take the wire on the headlight switch connector marked H that we used our meter on before in Step 2 - checking the power feed and snip it in two. Take the wire from H and splice on enough wire and a connector to attach it to relay connector "86". this turns the relay on and off when the headlight power switch is pulled in and out. Run the other side of the wire that we just snipped to relay connector "87", this feeds the 30 amp circuit into the wire that goes to the dimmer switch.

if you have not already done so, attach the relay to the firewall making sure that all wires and connections are safely protected. All other wires connected securely? Wires cut to length? No iffy connectors still attached? Wirenut on the old headlight power feed? Knock any non-headlight wires loose that need to be reattached/reconnected?

Reinstall the headlight knob into the switch, this will be temporary until we check things out. Once everything checks out then we will reinstall the switch permanently. Be sure that the modular connector is attached back on the top of the headlight switch.

You're done!

Step 9: lets review

you've done the following, right??

• connector block reassembled correctly
• fused wire connected from battery to fuse box
• 30 amp circuit from fuse box to connector 30 on the relay
• 10 amp circuit from fuse box to B1 on headlight plug
• headlight plug H to relay connection 86
• relay connection 85 to ground
• relay connection 87 to dimmer switch connector 3
• verified against schematic

Step 10: Action, Camera, Lights!

OK, first off - use some sense here. If something bad seems to be happening, disconnect the battery and resolve the issue. With that said...

action

Install the fuses into the fuse block

Connect the battery terminal keeping an eye out for large sparking when the terminal touches the battery post.

If all is ok, then proceed

camera

capture the moment

lights - oooohhh, ahhhh! or ahhhh, crap! ??

the moment of truth - pull the headlight switch out so that the lights go on

for those with "oooohhh, ahhhh!" be sure to test both hi and lo beams, make sure the front parking lights are working as well since we cleaned those connectors. Install headlight switch back into the dash

for you "ahhhh, crap!" folks, don't despair, lets figure out whats going on.

Step 11: Troubleshooting

OK, you know where the wires are, so lets start at the beginning, take a breath and turn brain on...:

Assuming that there is no sparking when you hook the battery back up, and neither headlight is working check the following in this order:



1. check for 12v DC in at the fuse box - if no power here then check both sides of the fused link. it might be blown indicating short in the new wire between battery and fuse box, look for cuts in the insulation or connectors touching metal. Did you really tug on the wire when you were running it thru the firewall? if so then you may have pulled it apart in the middle without tearing the insulation, replace the #10 gauge wire if there is 12v DC power at both sides of the fusible link coming off the battery.
2. check for 12v DC out on the 10amp fuse, if no power then fuse may be blown, check for symptoms as above.
3. check for 12v DC out on the 30amp fuse, if no power then fuse may be blown, check for symptoms as above.
4. check for 12v DC at headlight connector B1, if no power then wire between fuse box and switch bad
5. with headlight switch pulled out and into the on position check for 12v DC at pin 86 on the relay, if no power then check it at connector H on the back of the headlight switch
6. with headlight power switch off, check for 0 resistance between relay pin 85 and ground, a bad ground will not turn the relay on when the headlight switch is pulled out even if you have power on relay pin 86.
7. with headlight switch pulled out and into the on position check for 12v DC at relay pin 30, no power means bad relay (be sure to check diligently for a good ground or it will look like a bad relay)
8. If you have made it this far and everything looks good, you have an open wire/bad connector somewhere.
9. Leave your headlight switch on for the rest of these tests
10. check for 12v DC at pin 3 of the dimmer switch, no power means open between relay pin 30 and the dimmer switch, check the wire for bad connections
11. check for 12v DC on both pins 1 and 2 on the dimmer switch, no power on either indicates bad dimmer switch
12. figure out what position your dimmer switch is in, hi or lo, and check for 12v DC power on the corresponding lug on the connector block in the engine compartment, hi on the right lug, lo on the center lug. No power here means bad wire/connector between dimmer and connector block (should have been caught in step 2).
13. if you have not caught it by now, you have either missed something or you need to recheck your ground on the relay, otherwise at least one light should be on. its highly unlikely that both will be out.



If one headlight is working and not the other



1. check the connector block connections to make sure that all the wires are connected correctly and connectors are clean (should have been caught in step 2).
2. pull the offending headlight bezel and retaining ring and check for 12v DC in the headlight connector, if no power then bad wire/connector between connector block and headlight connector (should have been caught in step 2).

Images and Pictures

Figure 1 - Bosch 0-332-019-150 30 Amp Relay

Figure 2 - Headlight and blinker wiring block connector. Lug with green wire is hi beam power, brown wire is lo beam power, leftmost lug is parking light power.

Figure 3 - Headlight connector drawing

Figure 4 - Drawing of headlight switch w/circuit designations

Figure 5 - Dimmer switch drawing

Figure 7 - Simple wiring schematic for headlights and parking lights, click for full sized image

Addendum

Power Drop Information

Well, today I bought a new Sylvania H6024XV light to replace a broken one on my truck, so I devised a quick experiment.

I hooked up the lamp to an adjustable power supply so I could apply any voltage I want to it and monitor it with a DVM. I taped a white card to the wall and pointed the headlamp at the card from a distance of 8'. Then I mounted a Sekonic incident light meter on a tripod so I could read the brightness of the light reflected from the card. Took a few data points at various voltages and got the following:

Percentage of full light output at various voltages, with 12.6 volts being "100%" :

12.6v = 100%
11.5v = 75%
10.3v = 50%
8.7v = 25%

At 10.3volts they only put out 1/2 of their full light output!

The highbeam current on a 65w bulb is about 5.15 amps, 2 bulbs makes 10.3amps Consider that if the *total* resistance of all the wire, connectors, headlight switch and dimmer switch is equal to only 0.3 ohms (which isn't very much!), than with 10.3 amps flowing thru the circuit you will loose 3.09 volts in the wire and switches.

So, with a battery voltage of 12.6, the bulbs only see 9.5 volts. That's over 1/2 of Your potential light output thrown away right up front! The voltage loss on my '71 wiring was about 3 volts before I did the relays, now it's about 0.4 volts.

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