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Electrical Fog lights come on with headlights

  • Thread starter Thread starter sav22rem22
  • Start date Start date Jan 14, 2021
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    fog lights headlight switch

sav22rem22

5 Year Member
Feb 6, 2020
397
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North Carolina
Jan 14, 2021
#1
  • Jan 14, 2021
  • #1

So I recently tackled the project of re doing all the wires behind my headlight switch on my 89 GT. It’s always had weird affects on my car like the headlights seem to pull a crazy amount of power and my fog lights turn on when the headlights are turned on.

Upon taking the switch out I saw that there was nothing plugged into the fog light switch at all. I did also see that the Blue/Black wire and the Tan colored wire were just wrapped together. So I ordered a new headlight switch and fog light switch harness and switch. The picture above is what the current wiring looked like which is why I didn’t feel bad about re doing all of it. It was a mess. So after i finally got everything done and made sure to do it all right I wired up the fog light switch correctly and it still does nothing and the fog lights still come on even though they aren’t wrapped together anymore.

What could be causing this? I really suck at wiring and have next to no knowledge on anything wiring. So I’m really lost and confused and a little irritated that I spent all that time and money rewiring it just for it to not work. Any help is greatly appreciated. Here are a few more pictures of before and after the job below. I know my work doesn’t look the best but it’s my literal first time ever doing anything like this.

 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,224
17,909
224
Massachusetts
Jan 15, 2021
#2
  • Jan 15, 2021
  • #2
Sounds like a wire is still crossed somewhere. Double check the wire layout against this diagram, bottom right.



might want to replace that melted connector.

Mustang Headlight Switch Connector (87-93) - LMR.com

Replace your melted 1987-1993 Mustang headlight switch connector with this factory style replacement!
lmr.com

You might actually want to split off the fog lights and wore the independently. They are know to overload the wiring and cause fires, or melted connectors as you can see. Googke 87-93 mustang fog light fix.

Classic Mustang's Overloaded Headlight Switches - 5.0 Mustang & Super Fords Magazine

Read all about how to stop overloaded headlight switches by simply hard wiring your foglights to an aftermarket relay - 5.0 Mustang & Super Fords Magazine
www.mustangandfords.com
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,224
17,909
224
Massachusetts
Jan 15, 2021
#3
  • Jan 15, 2021
  • #3
Head/fog light wiring for reference

 

sav22rem22

5 Year Member
Feb 6, 2020
397
86
48
North Carolina
Jan 15, 2021
#4
  • Jan 15, 2021
  • #4
Mustang5L5 said:
Sounds like a wire is still crossed somewhere. Double check the wire layout against this diagram, bottom right.



might want to replace that melted connector.

Mustang Headlight Switch Connector (87-93) - LMR.com

Replace your melted 1987-1993 Mustang headlight switch connector with this factory style replacement!
lmr.com

You might actually want to split off the fog lights and wore the independently. They are know to overload the wiring and cause fires, or melted connectors as you can see. Googke 87-93 mustang fog light fix.

Classic Mustang's Overloaded Headlight Switches - 5.0 Mustang & Super Fords Magazine

Read all about how to stop overloaded headlight switches by simply hard wiring your foglights to an aftermarket relay - 5.0 Mustang & Super Fords Magazine
www.mustangandfords.com
Click to expand...
Greatly appreciated on the diagrams. I’ll get to looking as soon as possible. Yeah I don’t know why I forgot the picture but I did actually replace the connector and properly redid all the wires including the tied together fog light wires. Once again thanks so much for the diagrams
 

arnie93lx

Active Member
Oct 1, 2005
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29
Columbus, OH
Jan 15, 2021
#5
  • Jan 15, 2021
  • #5
Wow, that was a fire waiting to happen. Glad you got it repaired, someone jury rigged that wiring
 

sav22rem22

5 Year Member
Feb 6, 2020
397
86
48
North Carolina
Jan 16, 2021
#6
  • Jan 16, 2021
  • #6
arnie93lx said:
Wow, that was a fire waiting to happen. Glad you got it repaired, someone jury rigged that wiring
Click to expand...
Yep. I went for over a year without seeing any of that and I’m so thankful it didn’t burn me or my car to the ground. Unfortunately my whole car is sort of rigged together from the previous owners and I’ve been spending all my time fixing their mistakes rather than enjoying the car
 

DemonGT

Founding Member
May 24, 2002
871
51
49
Sparta,WI
Jan 16, 2021
#7
  • Jan 16, 2021
  • #7
When using my headlights and fog lights it would over load and shut off my headlights and fogs. Common issue, someone
on here or corral had a how to wrote up with a parts list to get from your hardware store and how to rewire the fogs to not over load the circuit. Someone may have it saved and could post it.
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,874
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203
polk county florida
Jan 16, 2021
#8
  • Jan 16, 2021
  • #8
Look for post #11 I think

Electrical - 92 GT Convertible - Fuse 13 Continuity Testing Question

Hey there, I have no interior dash lights, except the radio works and dome light and the exteriors are all good. Tried two dimmers, turned all the way down, fuse is good. Once I turn them up, no lights, hits "Dome Light on" and pops the fuse. So read I have to test the LB/R wire per the...
www.stangnet.com
 

sav22rem22

5 Year Member
Feb 6, 2020
397
86
48
North Carolina
Jan 16, 2021
#9
  • Jan 16, 2021
  • #9
Mustang5L5 said:
Sounds like a wire is still crossed somewhere. Double check the wire layout against this diagram, bottom right.



might want to replace that melted connector.

Mustang Headlight Switch Connector (87-93) - LMR.com

Replace your melted 1987-1993 Mustang headlight switch connector with this factory style replacement!
lmr.com

You might actually want to split off the fog lights and wore the independently. They are know to overload the wiring and cause fires, or melted connectors as you can see. Googke 87-93 mustang fog light fix.

Classic Mustang's Overloaded Headlight Switches - 5.0 Mustang & Super Fords Magazine

Read all about how to stop overloaded headlight switches by simply hard wiring your foglights to an aftermarket relay - 5.0 Mustang & Super Fords Magazine
www.mustangandfords.com
Click to expand...
Yeah I’m going to look tomorrow and try to find where the wires are crossed. My fog light switch does nothing and the fog lights come on when the headlights are turned on. So once I figure that out I’ll do the fix to put them on a different circuit. Is the fix you linked me the same one I saw jrichker post about on here a while ago? If I remember right that is
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,224
17,909
224
Massachusetts
Jan 16, 2021
#10
  • Jan 16, 2021
  • #10
Probsbly so. If you just search “fog light fix” it should pop up.

if you look at the wiring diagram, Ford wired the headlights and fog lights all through one single terminal on the headlight switch. As you’ve seen, this is not good
 

Blown88GT

Founding Member
Nov 13, 1999
2,283
524
164
Palm Beach Gardens, FL
Jan 16, 2021
#11
  • Jan 16, 2021
  • #11

'87-'93 GT Fog Lamp & Main Light Switch Fix

Main Light & Fog Lamp Switches - only affects GT's. In the February, 1991 edition of Popular Mechanics, the "Car Clinic" by Mike Allen had the following: Fogged Out Q: "I have a 1988 Ford Mustang GT. After about 20 minutes with my headlights...
www.stangnet.com
 
Reactions: DemonGT and General karthief

sav22rem22

5 Year Member
Feb 6, 2020
397
86
48
North Carolina
Jan 17, 2021
#12
  • Jan 17, 2021
  • #12
Blown88GT said:

'87-'93 GT Fog Lamp & Main Light Switch Fix

Main Light & Fog Lamp Switches - only affects GT's. In the February, 1991 edition of Popular Mechanics, the "Car Clinic" by Mike Allen had the following: Fogged Out Q: "I have a 1988 Ford Mustang GT. After about 20 minutes with my headlights...
www.stangnet.com
Click to expand...
Awesome, thanks!
 

90sickfox

Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
6,945
5,816
213
Jan 19, 2021
#13
  • Jan 19, 2021
  • #13
Check the wiring up front. They may have wired the fog lights to the headlights at the front of the car.
 
Reactions: General karthief

sav22rem22

5 Year Member
Feb 6, 2020
397
86
48
North Carolina
Jan 25, 2021
#14
  • Jan 25, 2021
  • #14
90sickfox said:
Check the wiring up front. They may have wired the fog lights to the headlights at the front of the car.
Click to expand...
That's also what I'm thinking. Going to check sometime this week and I'll update this thread with any findings. Thanks for the help
 
Reactions: 90sickfox
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