Headlights Turn Off...help!!!

[1992MustangGT]

I have a 92 Mustang GT 5.0 and I have a major problem with my headlights shutting off, which is scary as hell when it's dark outside and you can't see where you're going. It is random when they go off and usually when I turn them on high beam they will come back on, most of the time, but not all the time. So I purchased and installed a brand new turn signal/wiper switch (multifunction switch) and still the same thing. Didn't fix the problem.



However, when I removed the multifunction switch and looked at the wiring I noticed one of the plugs that plugs into the multifunction switch was melted (see picture--long, slender plug). I looked online at several Mustang parts suppliers (Latemodel Restoration, Mustang's Unlimited, Auto Krafters, Mustang's Plus) for wiring and plug replacements. I found a replacement kit from Latemodel Restoration that included a multifunction switch, a headlight switch plug and one of the multifunction switch plugs, but it's not the plug that's melted. I can't find that plug anywhere. Does anyone know what my headlight problem is (assuming it's not the melted plug) and where I can find a replacement plug for the one that's melted? Any advice would be appreciated. Thanks...

 

[Mstng93SSP]

I had the same problem with my '93. Headlights would work for about 5 minutes then shut off. My problem was a bad headlight switch. I replaced the switch and have not had a problem since.

Chris

 

[Justin81]

Check out this write up. www.corral.net/tech/maintenance/foglights.html I used it on my '87 gt and it fixed the problem for me. It also lets you have your fog lights on with just your parking lights.

 

[jdb3rd]

Check out this write up. www.corral.net/tech/maintenance/foglights.html I used it on my '87 gt and it fixed the problem for me. It also lets you have your fog lights on with just your parking lights.

That's what I had to do with my 87 and my 88. If I remember correctly it's due to the gauge of the wire being to small for the voltage needed to support both the foglights and headlights.

 

[1992MustangGT]

Thanks guys. I will definitely change the headlight switch and see what happens. Justin81, thanks for the link. It was very informative. I just got my parts in from Latemodel Restoration tonight so sometime in the next week I'll tackle this project.

Oh, another problem I forgot to mention when I described my problem was my windshield wipers quit working also and are stuck in the middle of my windshield. That's why I originally thought it was the multifunction switch malfunctioning. Anyone know what is causing the wipers to not work? It's not tied into the wiring on the headlight switch somehow is it?

 

[jdb3rd]

that sounds like the multi function switch on the column

 

[jrichker]

SEE Mustang GT Fog Light Fix to fix the problem. The stock wiring isn't up to the job and is overheating. The headlight switch & turn/multifunction switch are affected by Ford's wiring problem. Sometimes it overheats so badly that the plastic shells of the wiring connectors start to melt. This will show you how to add a relay to the fog lights to relieve the overload on the headlight wiring.

I did mine differently, but I had to build my own wiring harness for the fog lights. This is more trouble than it is worth for most folks. I left all the wiring on the stock light switches in place and used the fog light wiring to power the relay coil. The other side of the relay coil is connected to ground. I have an inline fuse that picks up power from the battery side of the starter solenoid. It is connected to the relay contact. The other relay contact is connected to the new wiring harness I made for the fog lights.

The advantage of making your own fog light wiring harness is that you can run 100 watt fog light bulbs. The stock wiring harness will not use 100 watt bulbs without overloading and causing a fire.

Unless you are good at electrical wiring, have the skills and tools (crimp tool, soldering gun, heat gun for the heat shrink tubing, etc.) I recommend that you stick with the Corral method.

Technical explanation of why the wiring and switches overheat.
You asked for it...

I= Current
E= Voltage
R= Resistance
W= Watts

Two 55 watt fog lamps =110 watts. Find the current in the circuit
I= W/E
110 watts/14 volts = 7.85 amps for fog lights alone.
Since the lighting circuit supplies headlights, taillights, and parking lights, etc.

56 watts 2 each GE Part # L3156 corner light 28 watts each
90 watts 2 each GE Part # 9004 headlight 45/65 watts each (low beam)
63 watts 2 each GE Part # L194 parking light 31.5 watts each
56 watts 2 each GE Part # L3157 tail light 28 watts each
265 watts Total

Total other exterior lighting current
I=W/E
265 watts/14 volts = 18.92 amps
18.92 amps other exterior lighting current
+ 7.85 amps fog light current
26.77 amps with all exterior lights and fog lights on.

The 12 gauge power feed wire to the exterior lighting switch is rated at 20 amps
26.77
- 20.00
6.77 amps excess current

7.85 amps used by fog lights
-6.77 amps excess current
1.08 amps to run the fog lights left if you stay within the 20 amp limit of the wire.
With 1.08 amp of current, the fog lights probably won’t produce any useable light.

Added resistance required to reduce fog light current to permissible 20 amp limit
R=E/I
14 volts/6.77 amps = 2.06 ohms
Resistor wattage
W=EI
14 volts x 6.77 amps = 94.78 watts
You would need a 2 ohm, 100 watt resistor.

Light bulb ratings from http://www.roadparts.com/catalog/section30.pdf
Radio shack resistor catalog - no matches , and no combinations that could be used to make a 100 watt, 2 Ohm resistor.
See RadioShack.com

Ohm’s law – in case you have any questions about my formulas - Ohm's Law Calculators

 

[Taino]

Had same issues, Turns out wires behind unit backed out came loose and caused short. Push wires in and make sure they are securely completing the connection.

 

[2000xp8]

By any chance did you put in higher wattage headlight bulbs ones that are white?
Those things melt down the connector you see in the pic above.

 

[Taino]

No, I've have same lights on for yrs. The slot you see burnt is for the hight beam. I got a new pigtail and replaced it and had to replace the head unit as well as it fried the back of the head unit as well

 

[2000xp8]

No, I've have same lights on for yrs. The slot you see burnt is for the hight beam. I got a new pigtail and replaced it and had to replace the head unit as well as it fried the back of the head unit as well

Taino, i was asking the OP lol, i figured yours was sorted out considering you know the problem.