Headlights stopped working - 1987 GT

[gt420hp]

My headlights stopped working and I am perplexed. The parking lights work fine, and the high beams work fine. I pulled the left and right headlight bulbs, they appear fine, no blown looking or destroyed filament. I checked the fuse, it was fine, but I replaced the fuse with a new one just in case.

If I turn on the high beams with the turn signal switch, I can pull it toward the driver and the high beams work. If I push it towards the engine, the high beams do not work. Any ideas of what the problem is? Is it the turn signal switch? or is it the actual flip switch to turn on the headlights gone bad? How can you tell where it might be?

I don't see any wiring out of adjustment, and nothing (no one) has been doing any wiring recently. It just stopped working...last time I used the headlights was about a week ago.

1987 Mustang GT - 5.0

 

[bt15]

It's sounds like the "multi-function switch" aka turnsignal switch. I had a similar problem occur on both my 1987 LX Coupe and my 1998 Expedition. You can get new ones from 5.0 resto or Ford. Ford runs about $70.00 and 5.0 resto's are about $40.00. Good luck!

 

[88stangmangt]

by-pass it to be sure that is how i found out that was my problem on my 87 gt.

 

[gt420hp]

how would I go about by-passing it to find the problem? Remove the headlight switch and try to get it to turn on that way?

 

[fivepointohgt]

It's sounds like the "multi-function switch" aka turnsignal switch. I had a similar problem occur on both my 1987 LX Coupe and my 1998 Expedition. You can get new ones from 5.0 resto or Ford. Ford runs about $70.00 and 5.0 resto's are about $40.00. Good luck!

I second that. I had the EXACT same symptons. I had to replace the multi-function switch and the wire harness to the headlight switch was melted, so I had to replace that too.

 

[dvs bullet]

Ford had a prob. with the GTs, they didn't upgrade the wiring harness for them, so when you have your fogs on you are putting a huge power load through the headlight circuit. It might be your sig switch, but when you repare it you are eventually going to have another prob. in another area down the road. I was chasing these probs for years, the only way that you could solve this prob is to install a relay for your fogs using the park lights for you reference and a new 12V source. You will still control you fogs through the stock switch, but you will be able to have you fogs on when you parks are on ( which looks really cool ), they will not turn off when you put on your high beams though. My car has melted switches signal switches wires, everthing, now it's not an issue. Good luck

 

[dude5l]

I agree with bt15 and fivepointoh, its the multi-funtion switch.

 

[gt420hp]

Thanks everyone for your posts. I'll go ahead and find a multi-function switch and let you know if that solves my problem...which it sounds like it will.

 

[Geo3]

My headlights stopped working and I am perplexed. The parking lights work fine, and the high beams work fine. I pulled the left and right headlight bulbs, they appear fine, no blown looking or destroyed filament. I checked the fuse, it was fine, but I replaced the fuse with a new one just in case.

If I turn on the high beams with the turn signal switch, I can pull it toward the driver and the high beams work. If I push it towards the engine, the high beams do not work. Any ideas of what the problem is? Is it the turn signal switch? or is it the actual flip switch to turn on the headlights gone bad? How can you tell where it might be?

I don't see any wiring out of adjustment, and nothing (no one) has been doing any wiring recently. It just stopped working...last time I used the headlights was about a week ago.

1987 Mustang GT - 5.0

Hi i was wondering if this solved your head light issue as I seem to have the same problem with my 87LX?

 

[jrichker]

SEE Mustang GT Fog Light Fix to fix the foglight 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.

Be careful not to use bulbs rated at more than 55 watt each with the stock fog light wiring. Using oversize bulbs can result in overheating the wiring harness and electrical fires. Definitely do the fog light fix first.

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 foglight 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