I replaced my light switch module located on left side of dash cluster with a new one. Previous one had fried, high beam wouldnt work and light would cut out at the worst times and it was just a mess. Replaced pig tail and installed new Module. I test out the lights, reg, high, fog lights. light come on fine, high beam wont come on and when I go back to nrmal reg beam doesnt come on URGH! I have to fiddle between hign n low to get reg lights to come on. So as long as I dont try to put on high beam lights stay on. All connection are A-ok so not sure where to go from here? Anyone have a diagram of what wires activate what on connector ? or could it be the turn signal swith on the steering colum that went bad ? any help would be appreciated
Light switch issues ???? Help!
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jcgafford
10 Year Member
i had close to the same issues. had to replace both the headlight/foglight switch and the turn signal/wiper assembly (multifunction switch). advance auto parts sells both under the bwd line. when you open the box you will notice that they are repackaged ford parts which is nice. also if you can google a coupon code for advanced and pay online for store pickup you will save you a ton of cash. i had to replace wires to it as well. this is a well known foglight problem and it cooks the wires to the multifunction switch.
fyi, this is a "bandaid" according to those that have gone thru it. while you have to replace these parts if the wiring and parts have cooked, it does not fix the reason they cooked. there are threads for the foglight fix in the forums. it causes problems with all your lights not just fogs.
bet you find this when you pull that multifunction switch http://img.photobucket.com/albums/v34/bmorrisj/S3010230.jpg
fyi, this is a "bandaid" according to those that have gone thru it. while you have to replace these parts if the wiring and parts have cooked, it does not fix the reason they cooked. there are threads for the foglight fix in the forums. it causes problems with all your lights not just fogs.
bet you find this when you pull that multifunction switch http://img.photobucket.com/albums/v34/bmorrisj/S3010230.jpg
Like previous post said, do a google search for the light fix. The wires running the light system are not large enough to support all the lights running at once. Sometimes it fries the switch, other times the wires. I started having the problem with my lights flickering on and off about a year ago. I have not fixed it yet, but i no longer run my fog lights and try to limit my highbeam usage. It is on my list of never ending things to do.
Joe
Joe
jcgafford
10 Year Member
yup. mine looked fine but was toast. replaced that, the wires and the gray connector. tellin ya advance auto parts.
Foglight/headlight switch problems
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
Multifunction switch interchange warning
Before you think about replacing the multifunction switch with one from the junkyard, here's some things to be aware of...
The problem is more common in GT models because they had fog lights on the same power wiring as the headlights. Ford undersized the wire and that caused problems.
A word of caution about multifunction switches is in order here. The multifunction switch (high/low beam, wiper, turn signals) are different for different years. 87-98 will work in any 87-89 car. The 90-93 switches only work in 90-93 cars. You can't put an early model switch in a late model car, nor can you put a late model switch in an early car.
Supposedly you can move the pins around to make the switches work in model years that are different from the car the switch came out of. I cannot verify that and haven’t tried it.
Other possible problem sources for the turn signal & headlight malfunction are the ignition switch, multifunction switch and the plastic shell that holds the turn signal wiring connector pins.
The following diagram is for 87-89 model cars.
Turn signal switch wiring:
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
Multifunction switch interchange warning
Before you think about replacing the multifunction switch with one from the junkyard, here's some things to be aware of...
The problem is more common in GT models because they had fog lights on the same power wiring as the headlights. Ford undersized the wire and that caused problems.
A word of caution about multifunction switches is in order here. The multifunction switch (high/low beam, wiper, turn signals) are different for different years. 87-98 will work in any 87-89 car. The 90-93 switches only work in 90-93 cars. You can't put an early model switch in a late model car, nor can you put a late model switch in an early car.
Supposedly you can move the pins around to make the switches work in model years that are different from the car the switch came out of. I cannot verify that and haven’t tried it.
Other possible problem sources for the turn signal & headlight malfunction are the ignition switch, multifunction switch and the plastic shell that holds the turn signal wiring connector pins.
The following diagram is for 87-89 model cars.
Turn signal switch wiring:
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