Note: Allpar does not take responsibility for the veracity of any information or opinions here, does not claim expertise, and is not responsible for any consequences. Please proceed at your own risk.
by Richard Henley for valiant.org and allpar.com
Daniel Stern recently sent me a kit to upgrade the headlights on “Old Blue” to European style (E code) headlights that take an H4 halogen bulb, and a pair of relays to run the new lights; just adding the switches adds brightness to the existing headlines by taking out voltage drop from the long stock wiring. In this article, we'll just install the relays - relatively inexpensive, but high quality. In a future article, we replace the standard DOT-type halogen sealed beam headlights with tightly focused E-code headlights (we also suggest preventing crashes by using amber turn signals). Without any further ado, however, here is the before-and-after for just the relays:
Daniel Stern Lighting has just about everything you need to upgrade your headlights, and then some. A few things that are not included are readily available at any parts house. The order sent to me included:
All I needed to supply was some wire, di-electric grease, a few screws, some shrink-to-fit tube, and solder. Most of the job requires common hand tools but one thing that will help make a more professional job is a crimper that will do the factory-style Packard connectors. I got mine several years back at a pawn shop, and it sure beats the $1.99 crimpers they sell at the discount stores. I would also recommend a soldering iron to solder the connections. About the only other specialty tool you may wish to have on hand is a multi-meter.
The relay mounts are designed so that they interlock, allowing you to make a bank of relays that will look like a factory installation. Everything in the kit appears to be the good stuff, no butt connectors here. I didn’t need everything in the kit for this install, but it’s always better to have more than you need.
Any electrical project requires some advance planning, so you can eliminate as many of the potential surprises before they come up. Dan Stern’s website is a gold mine of information, and provided two good ideas for this install:
I didn’t feel the need to hide the relays, but I could hide most of the wiring, and the part I can’t hide I can blend in with the factory style. On an A body like Old Blue the relays could have been hidden pretty effectively under the battery tray with the horns, but that would be a bit of extra work for both the installation and again if one needed replacing down the road.
Fortunately Daniel Stern has a great tech section on his website, and this should be read and taken to heart before starting this job. Some of the info there I already knew, and lots I didn’t, including a bunch of trivia on lighting development and what all the numbers mean. I wish the regulators would take a look at what he’s written concerning the blue “imitation HID” headlights that idiots seem to want to blind oncoming traffic with.
One of the best things about his website is that the tech pages come in a printer friendly version, so those of us who don’t have a computer in the garage (or a garage) can print it out and take it to the car with you.
After reading the relays page, you understand about voltage drop in the factory wiring system, and how a little voltage drop has a drastic affect on headlight performance. The wiring diagram for the Duster shows the headlamp wiring is a puny 18 gauge, and I can confirm this. In the past I installed halogen sealed beams, and only saw a marginal improvement; the best headlights in the world aren’t going to work without enough power, so measuring volt drop is the first step in determining where poor lighting problems are. Dan Stern’s website has a good description on how to measure volt drop, so I’m not going to go into it here.
My first readings showed a bit over 3 volts lost between the battery and the right headlight on both low and high beams. Ouch. Just out of curiosity I measured the drop between the battery and the alternator, almost a full volt dropped there. New battery cables have been on the agenda for a while, so I put them on, and for good measure added a ground strap from the alternator to the body. That solved the volt drop to the alternator, less than a quarter volt lost now, but at the headlights I was still showing a 2.8 volt drop on high beams and 2.6 on low beams.
One part that required a lot of thought was tapping into the alternator side of the charging system. Several ideas come to mind, but the easiest was to run a wire right from the stud on the back of the alternator. The problem is Ma Mopar used a terminal end with a big plastic shield to keep things from accidently getting to it and creating a short. Not wanting to eliminate the plastic shield, the solution came to me when I found a spare harness that had the plastic shield busted on the main charging system terminal. I reused the main charging wire from the spare harness to supply power to the relays, and fit the busted shield together with the original charging wire so it’s still shielded at the alternator.
Relay mounting location was another thing to think about. It had to be close to the front of the engine compartment to keep the wiring as short as possible. The location needs to be accessible enough that one can get to it to change a relay if necessary, but out of the way enough to keep it from accidental damage, and, needless to say, dry. I the garden hose to test spray through the radiator with the engine running, thinking that should simulate driving in wet weather. I found that the left side inner fender beside the battery is about the driest place there is toward the front of the engine compartment.
Please read the discussion over fuses vs circuit breakers which follows before using circuit breakers.
One place I differ from Daniel Stern is in the use of fuses for the headlight circuits. He and I agree that circuit protection is vital, but I prefer to have one circuit breaker over two fuses for my headlights. Circuit breakers will interrupt the current in case of a short as well as fuses will, but if it’s a momentary problem a circuit breaker will reset itself, possibly allowing you to see where you are pulling off to fix the problem. In practice only high or low beams should be on at one time, if they are both on at the same time you will ruin the headlight bulbs in short order. I’ve had a dimmer switch hang up once and had both beams on at one time; with a separate circuit protector on each beam, it will allow both beams to burn without registering a problem until the headlamps blow. A 15 amp circuit breaker is plenty to run two headlights just fine, but if the dimmer hangs up it will break the circuit letting you know you have a problem.
After this article was posted, Daniel Stern sent an email regarding using fuses vs circuit breakers. In disagreeing with him I wasn’t trying to say that his preferred method of using two fuses was wrong, but rather that it not the only way to protect the circuit effectively. Daniel Stern has far more expertise in automotive lighting than I do, and I certainly respect his opinion. What he’s written on the subject ought to be required reading for anyone engaging in the design, manufacture, and regulation of automotive lighting systems.
The two fuse method Dan recommends is the one to use for the absolute best in circuit protection for every instance other than the dimmer switch failure I mentioned, and as he pointed out, dimmer switch failure is so rare as to be almost unheard of. When manufacturers moved the dimmer switch from the floor to the column they dramatically reduced dimmer problems, as floor mounted switches are exposed to all the mud and snow that gets tracked in when using the vehicle in extreme weather conditions, leading to the corrosion that causes the problem.
His method is simple and straightforward: a short in the wiring blows the fuse, cutting power to the affected circuit completely and immediately. Fuses don’t reset themselves, so there is no danger of the circuit being reactivated before repairs have been made. Having a separate fuse for low and high beams means that a short in one won’t deactivate the other.
The single circuit breaker relies on some of the protection coming from “overbuilt” wiring. To eliminate voltage drop in the headlight circuit, the length of the wires from the switching device to the beams was shortened by about 50%, and the wire size increased from the stock 18 gauge and 20 gauge to 14 gauge. Since the breaker must trip if the low and high beams are on simultaneously, I used a 15 amp breaker that is only sufficient to operate either the low or high beams, but not both. Since a 7 foot length of 14 gauge wire is rated to handle 40 amps, even in the instance of a dead short, a 15 amp breaker will trip long before the wire gets hot enough to burn. Using a single breaker for both beam settings does kill both if you have a short in one, but only momentarily until the breaker resets, and if you switch beams as soon as you lose headlights, it will reset fairly quickly.
While dimmer switch failure is a very rare occurrence, I’ve had it happen on three different vehicles, each time on a vehicle older than 30 years and with over 100,000 miles on it. Most people don’t use 30+ year old high mileage vehicles for daily drivers, and fewer yet put such vehicles through the rigors of emergency vehicle service in a rural area during extreme weather conditions like I do, so for most the two fuse method shouldn’t be a problem.
Over the years the manufacturers have used variations of both methods, and if done properly, either way will work. I have talked with several automotive electricians on the subject, and the opinion about which method is best is divided, but all agree that both will work well if installed and maintained correctly. While the thought seems to be divided on which method of circuit protection is the best, all agree that the use of quality components is an absolute must. Daniel Stern and I may disagree on the best form of circuit protection, but we can both agree that he offers the absolute best components on the market.
Determining where to mount relays meant that the circuit breaker (or fuse) could be mounted in the same area, and the shortest routing from the alternator to the relays is to the core support and with the lighting wires to the battery. After test fitting the wire to determine the correct length, a ring terminal was installed on the other end of my salvaged 8 gauge charging wire, with 2 pieces of shrink to fit to support and protect it.
If you don’t have a spare harness, any piece of wire (at least 12 gauge) with a ¼” ring terminal soldered to the alternator end will work, or if you prefer to use the fuse holders that come in the kit, solder the ring terminals to them to hook to the alternator. The other ends will be connected to the relays.
Next up is the headlight wiring. When doing the rough cut on the wires, run them along the path they will follow, but make sure you leave a few inches extra, it’s much easier to trim off excess than to splice extra on. I used 14 gauge wires from the relays to headlights with the dual 87 terminal relays that come in the kit. The dual 87 terminal relays mean that you don’t have to splice the headlight power wires in route, they each connect to their own terminal at the relay. I also ran a separate wire for each headlight ground, they join when they get to the battery terminal. I wrapped a small piece of tape around the wires every foot or so to make sure they stayed together as neatly as they would in the factory harness. After the initial fitting I took the new wiring back off and to the workbench to do the finish trimming and install the connectors.
When installing connectors you want to make sure they don’t corrode or come loose at the connections. I tin the wire with solder before installing the terminal, crimp it securely, and if it’s something critical I add a bit of solder after it’s crimped. From here I’ll let the pictures do the talking for a bit.
When putting the terminals in the connectors, make sure you get them in the right position. If you get one wrong it’s not the end of the world, press the tang with something thin like a dental pick and slide it back out. The relay mounts are tricky to wire up, as there really is no good way to mark them before you start snapping the terminals in. This is where good notes come in handy.
Once you have the new harness built, the real work starts if you are going to hide the wiring like I did. If not, simply install your new headlight harness and fish the old headlight wires out at some point in the harness near your relays. Another option would be to install one of the male connectors to one of your existing headlight plugs and route the wires from that to the relays, if you don’t want to cut into your original harness. If you are going to hide the wiring like I did, you’ll to have to take the factory harness apart to install the new headlight harness in with the original harness.
First, measure where all the branches come out and the harness holders are mounted, so you can get everything back together the way it was.
Next, undo the old harness from the front lights all the way into the engine compartment where the relays are. If you have new harness wrap, you can cut the old wrap off, but I’m cheap so I unwrapped it carefully so I could reuse the wrap. The original wrap was ended at the right marker light connection, so that’s where to start unwrapping.
After you get the harness unwrapped you will have to remove the original hi and low beam wires as far back as where the relays are mounted. Inspect the harness carefully; you never know what future problems in your 35 year old wiring you might find.
If you have a late A body like mine, you can also remove the left headlight ground back to the main splice, but the right headlight ground also grounds the rest of the lights on the right front of the car. This will require clipping the wires and splicing them to remove the right headlight plug.
The high and low beam power wires need to be rerouted to the relays, as they are what activate the relays. Tin the wires and crimp them into the terminals and install them in the appropriate place in the relay holders.
After the factory headlight wires are installed in the relay holder, rewrapping the harness began. It takes a bit of care to get it wrapped factory style; the best tricks I can offer are to check the wrapping after every three or four turns and have a helper hold the loose end of the harness so you’re not fighting with it. Then mount the relay holders on the inner fender and connected the power wires to the circuit breaker, using a little di-electric grease on the breaker terminal.
I soldered the headlight grounds to one of the wires sticking out of my new negative terminal, eliminating future ground problems with the headlights. It took a bit more harness wrap than what came off the original harness due to the extra harness length added in the run to the relays; the harness is now a bit larger than it was originally, and I wrapped the parking light wires that were originally cloth tape covered, but the tape had disintegrated over the last 35 years.
Once the harness is rewrapped and reinstalled, install the relay holders, connect your power wires to the breaker if you used one instead of the fuse holders, and plug the relays and headlights in and test your wiring. A little di-electric grease in the relay and headlight connections will insure trouble free service for many years.
One thing I found I didn’t think out as good as I should have is that, when I closed the hood, the mounting tabs on the relays interfered with the hood closing. Since the mounting tabs aren’t needed for this install, I trimmed them off with a hacksaw and touched the relays up with a file. You have to look close to see the modification.
The finished wiring looks as good as the factory job, but the size difference with the added larger gauge wires is noticeable. There’s plenty of room on the inner fender to mount more relays if I decide to add driving or fog lights at a later date.
Now for the results of the relay installation.
When I first turned on the headlights, I noticed the halogen sealed beams were a lot brighter. The park and marker lights are also brighter now also, probably because they aren’t sharing a tiny 18 gauge wire with the headlights.
The real success of this operation is shown when the volt meter is hooked up. Before the conversion I was losing 2.8 volts on high beam and 2.6 volts on low. After the conversion the volt drop readings are .5 volts on high beams and .45 on low. This is a drastic improvement, better than two more volts going to the headlights (around 20% more voltage), and that makes a significant improvement in the lights. [Editor's note: voltage has a nonlinear relationship with brightness, so 20% more voltage is more than 20% more brightness.]
Installing the relay upgrade was a very noticeable improvement and I'm hoping the camera will show some of that. My wife has been driving the Duster, and she hasn't complained once about “can't see well at night,” which used to be one of her chief complaints about the old car. The relay kit by itself is certainly worth looking into if one desires to upgrade a stocker without making it look too upgraded.
I wish I had gone all out in hiding the install, just to see what could be done. Relay location was probably the biggest reason I didn't, as the only really well hidden spot I could come up with was under the battery box, and that idea didn't appeal to me from the ease of maintenance standpoint. The main power wire for the system could be hidden better in the main harness, but would involve a bit more work as the whole under hood harness would have to be unwrapped and rewrapped.
Thanks to Daniel Stern Lighting for providing the components and basic instructions. Also see preventing crashes by using amber turn signals at acarplace.com.
We strive for accuracy but we are not necessarily experts or authorities on the subject. Neither the author nor Allpar.com / Allpar, LLC may be held responsible for the use of the information or advice, implied or otherwise, on this site. This page is offered “AS IS” and without warranties. By reading further, you release the author and Allpar, LLC from any liability.
Wrangler weight, strength, and economy
Chrysler at Geneva
All Mopar Car and Truck News
Chrysler 300 Letter Cars
The Engine Cleanup Committee