Lighting Systems


    It was a dark and stormy night...we were trying to stay on the twisty Sawmill Parkway in rush hour traffic, and the four weak headlights on our 25 year old Plymouth Belvedere were not doing a thing on the glistening slick pavement.  I thought, boy, there has to be something wrong here. Well, many moons have passed and I' ve learned the answer is yes and no.

And by the way, if  you are sitting there smug, with a late model, or different brand vehicle, wake up and smell the coffee.  There are a lot of  pretty inadequate systems being used out there.  See Daniel Sterns web site for specific comments on that.   When I got my '85 Jeep Grand Wagoneer, I could believe how weak the headlights seemed.  I had gotten spoiled I guess.
 

Lamps

    Naturally, the place to start the discussion is the lamps. From the 1960s through the 1970s, all US manufactured vehicles were using sealed beams.  That is, the lens, reflector and lighting filament were all combined in a sealed unit.  An improvement in the sealed beam lamps was the halogen sealed beams, which are slightly brighter  because they are more efficient.  Otherwise, they are exactly the same and totally interchangeable.  A concours restoration vehicle would not want them because they are marked differently.  Other than that, they are more than worth the slight additional cost.

There are only a few variations on the older systems:
a) Two 7" round lamps combining high beam/low beam
b) Four 5" round lamps, two combining high beam/low beam, two high beam only.
c) Two Large rectangular lamps combining high beam/low beam
d) Four small rectangular; two combining high beam/low beam, two high beam only.

    All of the standard low beam/high beam lamps are rates 55 Watts/60 Watts.  That is the power each lamp should draw and does not directly indicate lighting power.   For the same 55 Watts, the halogen lamp will produce more light (see Lamp Efficiency below).   The European's have been far more creative and aggressive in the search to put more light safely on the road.  The result is the H4 Halogen lamps, and they can be purchased in the States.  These are sometimes referred to as E-code lamps, because they are designed to the European standards.  Technically, their legality will vary in the USA from state to state, depending on how each state defines adequate lighting.  What they generally lack is the three nibs that the headlight aiming machines used to use.  New Jersey state inspection used to check headlight aiming this way, and last I was resident there, would not pass a vehicle without the correct marks.  Hella makes H4 E-code lamps with the DOT aiming marks.  That's what has been on my car for about 10 years, because I got tired of swapping out the regular H4s every year.

    The heart of the H4 lamps are what we commonly call light bulbs.  They plug into the back of  a lamp and reflector assembly.  When the H4 bulbs burn out, only the bulb is replaced, not the lens and reflector.  The cost for the H4 bulbs are about the same as sealed beam halogens, but you must first invest in the H4 lens/reflector.
 

    Fog lights

    The advice I got from the rally crowd was to save my money and upgrade my headlights first, to H4s.  Only then should I go for fog lights if I still needed them.  It was good advice.  The H4 lamps  put most of the light below the headlight height, and if aimed right, very little will be reflecting off of the fog when on low beam.  In fact, recently I found this advice from Scott Harvey in Sports Car Graphic (May 1967) p 70 "Several makes of European headlights have a very flat top cut-off on both beams.  These lights are as good in snow or fog as any fog light I have used.  Also, they have a relatively low current-draw, so their bulbs have quite a long life.  They are not sealed beam, so they continue to function even if the lens is cracked.  These headlights double as good fog-lights and reliable..."  He then went on to explain that the other 4 lamps permited were a combination of 2 narrow driving and 2 wide beam aircraft lamps, all mounted above the bumper for better protection.

    My Wagoneer came with Marchal fog lights.  I got one to work, but the lens and reflectors were shot.  I have replaced them with H2 Cibie Tango 40s.  They put out a lot of light, but basically support the light in the low beam area.  Aardvark intl. has graphics showing the light patterns (and dimensions) of each of the Cibie auxiliary lamps.  Let me know if you find the same for any of the others (Hella, KC) and I'll add their links too.
   So in use, even the good foglights have been somewhat disappointing when combined with H4 headlamps. Granted, the mounting location on the Wagoneer is higher than ideal (above bumper). But in foggy conditions, the extra light was not found to be helpful on the small, twisty roads through New Jersey's hills. My guess is that the amber lens would be more effective combination with the H4 headlamps. There are also some larger foglamps (the Tango 40 is pretty small) with deeper beam patterns which are potentially better here.
 

    Lamp Efficiency

    Daniel Stern has created a chart showing the light output for each type of bulb, so you can determine for yourself what is better.  Lumens is a measurement of light, that's what counts most.  Watts is power consumed.  So, notice that an H2 bulb puts out 50% more light than an H3 for the same 55 Watts.  So, do you want a auxiliary lamp that uses an H2 or an H3?
    The halogen bulbs do not work well if they do not get adequate voltage.  In other words, if they don't get 13.5 Volts, they don't draw 55 Watts, and don't put out the lumens listed.  Below 12 volts, they are very unhappy.  Stern also has a big chart of small bulb types.
 

    System Efficiency

    Perhaps to save money, Chrysler wiring was just adequate to carry the current required on the Plymouths.  The A-bodies actually have lighter wiring than some of the mid and full size models, and only have a 15 amp (instead of a 20 amp) circuit breaker in the headlight switch.  The wires to the headlights are only 18 gage.  That's barely adequate to carry the 10 amps, two 55/60 Watt lamps can draw.  The main problem seems to be resistance in the connectors and grounds.
          Resistance does two things.  First it causes a voltage drop. Second it draws current.  If this is concentrated, it produces heat in one spot.  Watts = Volts x amps  It doesn't take too many watts to melt a plastic connector!
 

    Ye old electrical analogy:

    Think of Volts like water pressure in a pipe or garden hose, and amps as the flow rate (gallons per minute).
 

    Problem solving

    After staring at the shop manuals long enough, and reading and asking around, I decided to go install a relay system.  That seemed much easier than rewiring behind the instrument panel.  I already had a big hole melted in my headlight switch connector, and wasn't impressed with what the wiring diagrams indicated.  A 14 gage wire carries most of the current into the headlight switch, and a 16 gage carries it down to the dimmer, where it drops to two 18 gage wires, one for high (red) and one for low (black).   The connection that had failed was on the 14 gage input wire.  That said to me that I would have to beef up that wire as well as the ones coming out of the headlight switch, and each and every connection would have to be gone over, including the ones in the firewall connectors.  The engine harness was replaced about seven years ago with a nice repro from Year One.  Its a good repro. and every bit as inadequate as the original.
    Once the electricity is done with the headlamps, it has to return to ground.  The original design is not so bad here.  Each headlight got its own ground wire (black with white stripe) that goes to the radiator support and is held on with a sheet metal screw.  If there is paint underneath, or the screw doesn't tight anymore, or its corroded, then the final connection will be bad.  Also, realize that the only connection back to the negative of the battery and the ground of the alternator is through the engine block, and the only electrical connection from the body to the engine is the little strap way over on the firewall.  Running another ground wire from the battery negative to the radiator support can only help, and can be done very discretely.
 
 

    Relays

    Relays are remote switches.  Send them power and they turn a switch, Turn the power off, and they turn the switch off.
So, in a relay system, the high beam power is used to turn on the high beam relay instead.  Ditto with the low beam.  A relay only draws a drop of current so what was barely adequate becomes super overkill.  The real power is fed to the relays directly from the alternator or battery using as heavy of a wire as required AND a circuit breaker or fuse.
 

    Parts

    The hardest items to find are good grade connectors and relays.  My sources were West Marine Discount, Waytek Wire, and Radio Shack.   Marine duty stuff is more moisture resistant, the wire strands are all tinned, and sure it costs more.
I was going to use the automotive circuit breakers that reset themselves (just like the ones in the Chrysler and AMC/Jeep headlight switches)  but instead went for the buss fuses in a sealed marine fuse holder.  Tough call for me.
    Relays can be purchased in two patterns, 5 terminal and 4 terminal.  In both, two terminals are for the signal, in & ground.  In the 5 terminal, the two outputs can be arranged to be both on and both off.  That can simplify wiring.  One can go to the left light and the other to the right light. Or, one can be used to feed your auxiliary lamps.  That way, your fogs can only turn on when the low beams are on, or your driving lights only when the high beams are on.
    But, be careful when buying 5 terminal, they also come as double pole (DPST).  In this arrangement, one output is on when the signal is on, and when the signal is turned off, the other output is on.  Something is always on. Ooops.
 

    Assembly

    I couldn't find a good replacement for the headlight connector.  The one NAPA carries was unimpressive, although its been suggested since then that Autozone may carry a decent one.  I disassembled the harness, and used my original Chrysler harness as reference.  If you don't have two harnesses. then you will want to do some careful measurements or trial fits of the wire lengths on the car.

   1.  Removed the headlight bezels and headlights.
    2. The power for both headlights goes into the drivers side headlight socket.  The wires out to the left headlight is crimped together with the power lead on to the connector.   So the bundle going to the connector has two reds wires (high beam in, left high beam out), two black wires (low beam in, left low beam out) and black with white stripe (right side ground).  I decide to use the original wires to signal my relays on the left fender.  Since I wanted the socket, I clipped the wire bundle, and reconnected the reds and the blacks by soldering.  The ends were then sealed with liquid electrical tape and cold shrink tape.
    3. The left head light wire bundle was also clipped, but only an inch from the connector.  The leads were then ran to the left fender.  Connectors made for the relay sockets were then crimped and soldered on.
    4. Fun part. not. Slipping a cotter pin in the flat T of the headlight connector, the catch was depressed and the metal clips pulled out.  This is when I found the crimps on the new harness weren't that great.  In fact the Chrysler crimps were observably better upon close inspection.  Then each metal connector was gently placed in a wood jaw bench vise, and the crimps opened up.  I used an ice pick and small screw driver working in parallel to the wires from the insulation crimp toward the front.  It is possible the Packard 56 series 12 gage connectors would work here.  The 14 gage ones are too small, but otherwise look and fit right.  Made up a new high and new low beam wire out of 14 gage wire connecting  the relay connector to the head light sockets.   Instead of joining the wires in the headlight sockets, I spliced them in line.
    5. Made up two 12 gage wires with in line fuses to carry power from the alternator "bat" stud to the relay connectors.  The connectors were only for 14-16 gage, but by soldering as well crimping, I am sure I have very good connections.  Same with the 18 gage signal wires soldered to the same  14-16 gage connectors in step 3.
    6. Made up a bracket for the relay connectors with some sheet steel and  some old rubber feet electronic cabinet(radio or something) .  Holes already in fender from former air conditioning  system.
    7. Made up new ground wires for each headlight, a new ground to from the battery to the radiator support (12 gage marine wire soldered to a very sad and corroded unused lead on the Belodon battery cable, soon to be replaced).  Made a second  ground point on the battery side of the radiator support just for the headlights using a self tapping machine screw and nut left over from the speaker replacement on the Grand Wagoneer.  see, AMC still helping Plymouth ;)

Matt's Vehicles Page
'67 Barracuda
'85 Grand Wagoneer

More Tech:
Fuel Delivery Facts and Figures
Improving Forward Lighting & Electricals (You Are Here)
Ignition Wire Comparison
Handling Theory for late-'60s to mid-'70s Mopars

Oct 13, 2001 rev March 22,2004