Electrical Interior lighting issue

J

Jack1424

New Member

Sep 15, 2020

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0

1

Pensacola

May 21, 2021

#1

• May 21, 2021

• #1

I tried doing a search but could not pinpoint what I’ve got going on specifically. I’ve got a 1990 GT, all original, and recently when I attempt to turn my lights on, nothing inside is illuminating. Exterior is illuminating just fine with zero issues. Dome light works as it should. But I’m getting no instrument cluster lights, radio lights (factory radio that still functions as it should) and lighting for environmental controls. Any help would be greatly appreciated.

 

General karthief

wonder how much it would cost to ship you a pair

5 Year Member

Aug 25, 2016

27,872

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polk county florida

May 21, 2021

#2

• May 21, 2021

• #2

There is a roller on the dash pod by your left knee. Roll it back and forth slowly tell us if they flicker.

 

J

Jack1424

New Member

Sep 15, 2020

10

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1

Pensacola

May 22, 2021

#3

• May 22, 2021

• #3

I went ahead and tried rolling the dimmer switch and no flicker. However the dome light will still turn on via the dimmer switch. Could it be a bad fuse? Or should I just try swapping out the dimmer switch and/or the actual headlight switch as well?

 

7991LXnSHO

wanna catch the space herp

10 Year Member

Sep 1, 2010

7,387

2,745

194

Kearney, NE

May 22, 2021

#4

• May 22, 2021

• #4

Check to see if there’s power to the rheostat at the right time for your dash lights to be on. If there is, I’d replace that.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,218

17,902

224

Massachusetts

May 22, 2021

#5

• May 22, 2021

• #5

I believe there is a 5 amp fuse. I am poolside at the moment so can’t grab my wiring diagram to pull up the page.

 

KRUISR

10 Year Member

Apr 16, 2015

1,804

903

143

May 25, 2021

#6

• May 25, 2021

• #6

The 5 amp fuse circled is between the rheostat and the rest of the interior/gauge light circuit (instrument cluster, radio, etc.).

 

J

Jack1424

New Member

Sep 15, 2020

10

0

1

Pensacola

Jun 14, 2021

#7

• Jun 14, 2021

• #7

Just to update on this thread, I pulled the dimmer switch out and upon inspection, noticed that some of those finely coiled springs on the wheel had broken, thus leaving me to believe that was my problem. I found an OEM replacement dimmer switch on eBay that was in good condition so I bought it for 30$. I just got it today and tested the new switch out, and now all my interior lights are coming on but only when the dimmer switch is selected to the dome light. Do you guys think it’s a bad switch or a wiring issue with the car? At least I’m making some progress…

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,218

17,902

224

Massachusetts

Jun 14, 2021

#8

• Jun 14, 2021

• #8

Can you measure the output voltage on the blue/red stripe wire coming out of the dimmer? Should be progressive up to 12v as you spin the dimmer wheel

 

Reactions: Jack1424

7991LXnSHO

wanna catch the space herp

10 Year Member

Sep 1, 2010

7,387

2,745

194

Kearney, NE

Jun 14, 2021

#9

• Jun 14, 2021

• #9

First, did the summer fix your dash lights? OEM used is not the same as NOS. The rheostats are a common failure point, and have been forever.
Second, The interior lights should come on in the on position And when door is opened. If your. dash. Lights work now, and TBE dine light comes on when switched, I think you can move on from the dimmer dash switch.

 

J

Jack1424

New Member

Sep 15, 2020

10

0

1

Pensacola

Jun 16, 2021

#10

• Jun 16, 2021

• #10

Mustang5L5, I did what you said and I think you may have helped me pin point it. Upon looking at the blue/red wire connection up on the light switch itself (not the dimmer switch side) it will not stay secured into connector for the light switch. So I’m thinking it’s the blue/red wire. Would you all agree? And if so, is it an easy job to swap that wire out? Thanks guys

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,218

17,902

224

Massachusetts

Jun 16, 2021

#11

• Jun 16, 2021

• #11

If you can do butt splices it’s pretty easy. Here’s a new plug

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

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

lmr.com

 

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jrichker

StangNet's favorite TOOL

In Remembrance. Thank you for your contributions

Mar 10, 2000

27,512

2,813

234

Dublin GA

Jun 17, 2021

#12

• Jun 17, 2021

• #12

The plastic shell often fails to hold the connector pins in place. If the connector shell isn't melted, a dab of high temp hot glue on the wire side of the plastic shell of the connector will hold the wire in place.
The small hot glue guns and high temp hot glue are available at Walmart or hobby/craft stores. for $10-$12

 

Reactions: Wayne Waldrep, Jack1424 and General karthief