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I recently got tired of the dim sealed bulbs and upgraded to a pair of H4 conversion lamps.
The bulbs I chose were 55 W low and 100 W high. I knew it was time to upgrade the wiring harness.
As many of you know already, the existing wiring harness is wired in such a way that high beam indicator light is wired in series with the low beam bulb. This is enough to trigger both the high beam and low beam relays. End result the low beams come on with the high beams. I figured 155 W per bulb would likely cause a bulb to blow and damage the housing.
This is how I kept the low beams from turning on with the high beams. Tapped into the common (which is switch power, 12 V when the selector switch for the headlights is on) and the switched ground for the high beam on the OEM headlight plug. Then used the high beam switched ground and common to drive a 5 pin relay (one with the 87a terminal). This relay provides the ground to the headlight power relay. If the headlight selector is set to highbeam, then the lowbeam relay is no longer grounded and turns off the low beams.
I used two low beam relays, as to not be left out in the dark if one fails. The power for the relay coil on the highbeam and lowbeam relays comes from the common off the OEM plug. If tied to a constant power supply, such as the positive terminal of the battery, the low beams will always be on.
The high beam indicator lamp will not illuminate with the circuit how it is drawn, but heck if 100 W highs don't remind you the highs are on, others will.
Hope it helps. And don't forget to size fuses around 1.5x the sum of the total current that will be running through them.
Also, the relays used where resistor suppressed, but I don't think this is entirely necessary.
Here is the headlight relays wired up. The Ground switch relay is not shown and is currently tucked behind the battery on the truck. I mounted the relay block between the pickup's fusebox and the cowl, tucked underneath the lip of the hood seat.
I've had the headlights wired up for a few months now and it has been great being able to see on the windy North Idaho Roads.
Put headlight guards on to protect from rocks. It is simply expanded metal held on with some #6 self drilling screws into the existing headlight grill
The DOT here likes to pour gravel on the highways in winter. I lost an offroad light and now have several chips in the windshield from the flying rocks.
If it is important to have the Highbeam indicator light to work, modify the highbeam relay as the following diagrams show.
The first diagram involves hardwiring the indicator light, or installing a new light. It also requires a 5 pin relay with two NC contacts (type 87b contact).
The second diagram involves a 1N5404 (3 amp diode) or equivalent, a 1 watt 10 ohm resistor, and a 5 pin relay with two NC contacts (type 87b contact).
What program did you use to make the wire diagram? I work with ATV harnesses, so something like that could be useful for my stuff .
Anyway, looks like a pretty good setup. Just wondering, what size of wire did you end up running? It looks like around 10 gauge, I suspect factory was 14 gauge, so a pretty good upgrade in wiring (new is almost always better anyway vs 30+ year old wire).
atcfixer, I used MS paint for the wiring diagrams.
I ended up running 10 AWG to the driver side low beam to compensate for voltage drop and 12 AWG for the passenger low beam. I used 10 AWG for both of the high beams. On the relay circuit I used some thick insulated 12 AWG because I had it lying around. All connections are crimped, soldered, and sealed with dual wall shrink tubing.
My bet is that the headlight circuit will outlast the tired 22re in there
Wow someone that actually knows what adhesive heat shrink (dual walled) is and uses it! I ran out a few automotive parts stores and the guys over the counter had no clue what I was talking about lol. NAPA has some, but it isn't the greatest quality when you shrink it a lot.
I'd agree, your wires will outlast the wiring on the engine probably, let alone the mechanic parts, assuming you used good quality wire (GXL is great for the engine compartment good for up to 105C and is what OEM uses atleast for the newer stuff).
I was hoping you used an actual program, paint works, but it's kind of slow and you can't just feed it data and generate a harness l.
Great electronic component distributors are Mouser and Jameco.
Mouser has a more user friendly search features and cheap shipping. ( i got heat shrink in a 3" DIA tube that was 7' long and the rest of the order came in a 12x12x8" box. Grand total for shipping and handling was under 9 dollars.)
03-31-2017, 09:55 AM
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