Underdash courtesy lights
Underdash Lights
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Junior User
Joined: Jun 2012
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Underdash Lights
I scored 2 underdash lights from the local Pull-a-whatzit, my question is where does the underdash courtesy lamp harness extension plug into the factory harness? This is not an original option for my model truck, but I do have working doorjamb switches and dome light.Great site, always helpful.
Thank you
1978 F150 Ranger 4x4 Shortbed
Thank you
1978 F150 Ranger 4x4 Shortbed
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
Originally Posted by BigMightySam5600
This is not an original option for my model truck. 
Originally Posted by 78&79F250
Hopes this helps.
> > COURTESY LAMPS and WIRING 1974/79 F100/350 ~ ILLUSTRATION SECTION 137 ~ PAGE 7 < <
The 1973/79 Ford Light Truck Parts Catalog is available on a CD from hipoparts.com / FTE members: 78&79F250, mikeo0o0o0, jermafenser (and etc) are using this CD version, but not I.
I have an original FoMoCo microfiche viewer, original catalogs on FoMoCo microfiche slides. Have 4 editions of this catalog: 10/1979, 10/1981, 10/1986. final printing 10/1988.
Posting Guru
Joined: Nov 2008
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From: Halifx Pa
As Bill said all trucks were wired for this, just your truck did not have this option just like mine didn't. I bought a pair of courtesy lights off of flEbay along with the wiring harness. As shown in the second picture it shows the plug you would hook your harness too. All of our trucks were set up to accept all possible options. It is very intuitive as far as plugging in the harness. If you look under the dash, on each side is a circle cut out as its a two layers. I placed mine there and the screw holes are already there to. If you just pulled the lights and did not get the wiring harness I suggest you go back and get the rest of the wiring. While you at it see about getitng the ash tray, and glove box lights too. The plugs are at those locations as well.
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Junior User
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Courtesy Light Connections?
What color are the wires coming from the factory harness to the plug? The 12V keyed has three open slots. I have ash tray light (coming from econoline turn signal switch) and open stock receptacle (blue/red for stock ashtray light) and glovebox light operational as well, there is an open brown connector(oil pressure?) and a connector with a black/blue wire with an open blade in the receptacle, jumping this open blade to the courtesy lights works but is constantly hot. I know there is some harness part # unknown that plugs into the stock harness and jumps another lead to the courtesy lights????
ok
thx
ok
thx
Last edited by BigMightySam5600; Sep 14, 2012 at 07:02 PM. Reason: Error
Moderator & parts slinger
Joined: Feb 2007
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From: S/W Missouri, Polk county
I gave all the help I could, even though some point out it was all wrong or incomplete.
Anyway....at least I tried......
I would think you could tap into the dome light power wire, that is what I would do if I did not have or could not find the plug behind the dash.
Maybe at plug #11401 ?? Or the door jam switch, not the power in side, but power out when pin is out to close the loop and provide power to the dome??
Anyway....at least I tried......
I would think you could tap into the dome light power wire, that is what I would do if I did not have or could not find the plug behind the dash.
Maybe at plug #11401 ?? Or the door jam switch, not the power in side, but power out when pin is out to close the loop and provide power to the dome??
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Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
Here's the illustration Bill was reffering to. There is a wiring harness for the courtesy lights that would probably simplify the proccess.
In the picture, ignore the 14677 relay, that's for the roof mounted marker lights.
Wiring harness, courtesy lights
77-79 F100-350 Reg & Supercab
D7TZ-13A709-A
Green Sales, Cincinnati, OH has 5 (800)543-4959
Wesley Obsolete Parts, Liberty, KY has 2 (606) 787-5293
Parts International, Farmers Branch, TX has 2 (972) 241-8730
Click on the link to view the illustration from the ford parts catalog.
In the picture, ignore the 14677 relay, that's for the roof mounted marker lights.
Wiring harness, courtesy lights
77-79 F100-350 Reg & Supercab
D7TZ-13A709-A
Green Sales, Cincinnati, OH has 5 (800)543-4959
Wesley Obsolete Parts, Liberty, KY has 2 (606) 787-5293
Parts International, Farmers Branch, TX has 2 (972) 241-8730
Click on the link to view the illustration from the ford parts catalog.
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From: Halifx Pa
The plug that 77&79F250 shows in the picture looks to be the plug you want to use. I found mine behind the dash in the area of the radio, ash tray. As far as colors of wire for a hard wire job, I am unsure and do not remember off hand.
Hotshot
Joined: Apr 2009
Posts: 14,333
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From: Stanley, VA
The factory wiring diagram shows the under dash courtesy lights wiring is black w/ blue trace and tie into the dome light wiring at C-702 (connection 702) the notes show C-702 left hand side behind instrument panel. The plug will be a brown connector with two sets of wires, one set black w/ blue trace and one green w/ yellow trace.
Go here to check out the factory diagrams. Right now they aren't finished with '78 but, for this, you can use the '79 copy.
You want page 8, section 1E.
1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net
Go here to check out the factory diagrams. Right now they aren't finished with '78 but, for this, you can use the '79 copy.
You want page 8, section 1E.
1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net
Logistics Pro
Joined: May 2010
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From: Regina, Saskatchewan
I just picked up a set and will try to describe how they mount...
There should be a 1" recessed circle on the under-side of the dash directly below the glove box (dead center). There's basically 2 layers of steel to make this circle, with 2 small holes drilled in the middle of the recessed circle. Once you find it, it's easy to install. The bent tab on the light socket goes in the hole closest to the seat. The second hole is for a self-tapping screw. Install as described, hook up the wiring, and Bob's your uncle when you open the doors.
That's for the passenger side... The driver's side is directly below the 9 o-clock position on the steering wheel, same under-side of the dash.... same recessed 1" circle with 2 holes. Hard to miss.
There should be a 1" recessed circle on the under-side of the dash directly below the glove box (dead center). There's basically 2 layers of steel to make this circle, with 2 small holes drilled in the middle of the recessed circle. Once you find it, it's easy to install. The bent tab on the light socket goes in the hole closest to the seat. The second hole is for a self-tapping screw. Install as described, hook up the wiring, and Bob's your uncle when you open the doors.
That's for the passenger side... The driver's side is directly below the 9 o-clock position on the steering wheel, same under-side of the dash.... same recessed 1" circle with 2 holes. Hard to miss.
Mountain Pass
Joined: Jul 2020
Posts: 155
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I just picked up a set and will try to describe how they mount...
There should be a 1" recessed circle on the under-side of the dash directly below the glove box (dead center). There's basically 2 layers of steel to make this circle, with 2 small holes drilled in the middle of the recessed circle. Once you find it, it's easy to install. The bent tab on the light socket goes in the hole closest to the seat. The second hole is for a self-tapping screw. Install as described, hook up the wiring, and Bob's your uncle when you open the doors.
That's for the passenger side... The driver's side is directly below the 9 o-clock position on the steering wheel, same under-side of the dash.... same recessed 1" circle with 2 holes. Hard to miss.
There should be a 1" recessed circle on the under-side of the dash directly below the glove box (dead center). There's basically 2 layers of steel to make this circle, with 2 small holes drilled in the middle of the recessed circle. Once you find it, it's easy to install. The bent tab on the light socket goes in the hole closest to the seat. The second hole is for a self-tapping screw. Install as described, hook up the wiring, and Bob's your uncle when you open the doors.
That's for the passenger side... The driver's side is directly below the 9 o-clock position on the steering wheel, same under-side of the dash.... same recessed 1" circle with 2 holes. Hard to miss.
these holes correct?
Laughing Gas
Joined: Nov 2016
Posts: 853
Likes: 62
From: Oxnard
The correct location is the ones that are within the circle that has three small pre-drilled holes with the single larger hole forward. That larger holes allows the light fixture mounting tab recess to prevent the fixture from moving side to side.