After getting a mustang dome at a wrecker today, I thought I'd try and and see if I could try and make all three bulbs illuminate when the door opens, rather than two of the three sitting unused for the majority of the time.
This method leaves the vehicle's wiring untouched and only modifies the dome. Both switches still function as normal without any side effects. Cheap and easy to do, shouldn't take longer than an hour. Of course, I nor FordRangerForums is responsible for any damage to your vehicle. Proceed at your own risk.
Things you'll need.
Wire. A few feet should do. I wouldn't go any thinner than the dome light's original wiring, but not too thick either.
Two diodes. These diodes
should work.
Click Here (SB5100 Diode)
A pair of needle nose pliers wouldn't be a bad idea.
A soldering iron and solder
A power supply capable of delivering half an amp at 12 volts or better (for testing purposes)
A multimeter.
A screwdriver
And of course, the dome.
First off, we need to pop the dome apart. To do this, there are four Philips screws, location marked by the four red X's.
Remove those and the white plastic should come right out. If it doesn't, gently push on one of the switches to pop it free. Fear not, there aren't any pieces that are going to go flying.
Now turn the board around so that it looks like this.
Note the bolts numbered One, two, and three. You'll be testing your dome light with these bolts. You should find the following is true.
1 - Constant Power
2 - Ground
3 - Door Circuit
If it isn't, adjust accordingly.
Be careful to wire this up correctly! If you don't, you risk burning your truck to the ground.
You should see that the various bulb's terminals are marked. We'll be only making use of three of the contacts.
Yellow boxes with a black X inside designate ground. Blue boxes designate the door circuit. Green and orange boxes designate the 'always hot' lead.
After you're sure that the domelight ohms out properly, we'll start building the circuit.
This is where some alligator-clipped jumper wires will be handy.
Take your diodes and connect them as shown by the purple 'wire' going from mark to mark. Make sure to orient them correctly, otherwise it won't work properly. They should allow current to flow from the center festoon bulb but not back to it.
Note that the orientation shown may or may not be correct for your specific diode. Simply flip the diode around if it doesn't work at first.
Once you have your jumper wires connected, apply power and see if the lamps illuminate properly. They should be on regardless of what position the switch is in. But of course, if terminal 1 is powered and 3 is left open, they should operate only by the switches and the center bulb should be dark no matter what way the switches are pointing.
All three bulbs should
only illuminate when terminal three is powered.
If it works, take the bulbs out and solder on some wire to the
outside of the festoon's clips, taking care to route the wire so it doesn't get in the way of anything or potentially shorting anything out. Once that's done, test it again to make sure it still works.
If it does work, the following should be true, spoken as if it were mounted in the truck.
- When the door is open, all three bulbs come on regardless of what state either switch is in.
- When the door is closed, both outer bulbs should turn on and off independently of each other. The center festoon bulb should not be active until either the door is opened or the cargo light switch is turned on.
- When the cargo light switch is on, all three bulbs should illuminate, again regardless of what position either switch is in.
If this all is true then you're done. I, however, would recommend leaving the domelight running outside the truck for an hour with all three bulbs on. There's a reason for this.
Diodes have a forward voltage and with this produce heat. If they get too hot to hold onto you may need different diodes. You should be able to hold the wires and the diode barehanded indefinitely. Cool to the touch is okay, warm to the touch is okay, but hot enough that you can't hold it is a warning sign. Swapping the diodes may be necessary, but shouldn't be.
Warnings:
-If you don't remove the bulbs before soldering to the contacts, you'll end up ruining the bulb. While the bulbs are cheap, you may be mislead into thinking you damaged the actual dome circuit by accident.
-Make sure your diodes can handle upwards of 16 volts and at least five amps of current each. While at most you'll see 15 volts from your truck and it doesn't draw 5 amps, stick to these parameters otherwise you may find yourself with a smelly, hot, mess of melted diodes, which could potentially set your headliner on fire.
-When soldering, be careful not to melt the plastic housing.
-It is advisable to use heatshrink tubing over the diode to prevent it's leads from shorting out. However, leave the inner bulb contact uncovered otherwise the bulb may not receive power.
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This is the first 'how to' I've ever done, so I hope it's easy to understand. If there is any confusion, please, do not hesitate to tell me so I can clear it up. I hope you enjoy your modded dome light.
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While I was browsing YouTube, I was watching a couple videos about diodes. Picking out diodes can be very tricky, so I thought I would provide some helpful information on the subject.
In this application, a Zener diode is the worst type of diode to use, and the video on it will explain why. I'd hate to hear somebody burned their truck down to the ground, so I thought I'd try and help to prevent that with a little more knowledge explained by someone more qualified than me.