Author Topic: Interior Lights Only Work When Key is Turned - 68 DeVille  (Read 202 times)

Offline Bentley

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Interior Lights Only Work When Key is Turned - 68 DeVille
« on: November 29, 2017, 06:31:31 PM »
Hello,

When I open the door, the interior lights do not go on until I insert the key and turn to either the accessory or on positions. Same thing for the glove box light and the trunk light. Also, the presets on the aftermarket stereo get deleted each time I shut the car off. The body shop was the last place that worked on it, so they must have done something. I picked it up from them last summer, and didn't notice it until now that the days are shorter. Any ideas on what may be causing this?

Thanks,
Wes
Wes Bentley
CLC # 30183

Offline Glen

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  • Name: Glen Houlton
Re: Interior Lights Only Work When Key is Turned - 68 DeVille
« Reply #1 on: November 30, 2017, 12:04:51 AM »
Sounds like the car has been rewired.  Maybe a past owner had a battery drain problem and this was his fix. 
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Offline m-mman

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  • Name: Jim Crabtree
Re: Interior Lights Only Work When Key is Turned - 68 DeVille
« Reply #2 on: November 30, 2017, 03:32:31 PM »
A car's electrical system is divided into two general parts. Things that get power when the key is on (run or accessory) and things that get power all the time. (interior lights, trunk lights, clock)

The back of the key of course gets power all the time and then sends it out when it is switched on. Not sure about 1968 but commonly the fuse box has two separate areas. One that is powered all the time and one that is key activated.

An aftermarket electronic radio has TWO power wires. one that should get power all the time (to maintain the clock and presets) and one that is keyed. (powers the tuner and amplifier)

As mentioned above someone has moved the connections to the wrong places.
There is no way to diagnosis it without tracing the wires (and fuses) to see what it powered when and then putting things back to the way they should be.
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Offline TJ Hopland

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Re: Interior Lights Only Work When Key is Turned - 68 DeVille
« Reply #3 on: November 30, 2017, 05:05:35 PM »
I too am not sure how they were doing it in 68 but slightly later there were 3 fusible links on the starter battery terminal.    One to the headlight switch, one to the key which then fed half the fuse box, and one to the rest of the fuse box for the stuff. 

I wonder if the fuse box link blew or was damaged and something is back feeding that side from the key side?   With aftermarket stereo we know there was at least some rewiring going on.  Its also possible that a back feed jumper was installed as the 'fix' when the link was damaged whenever or whoever that happened.   
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Offline Bentley

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Re: Interior Lights Only Work When Key is Turned - 68 DeVille
« Reply #4 on: December 05, 2017, 03:04:00 PM »
Thanks for your help, everyone. I'm working on it.
Wes Bentley
CLC # 30183

Offline Highwayman68

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  • 68 Fleetwood Brougham
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  • Name: Mark Demyan
Re: Interior Lights Only Work When Key is Turned - 68 DeVille
« Reply #5 on: December 05, 2017, 05:22:34 PM »
Hi Bentley,

Do you have a Shop manual? I like to provide page references to help make the answers easier.

Just a quick test, try the horn with the key not in, if it doesn't work that will mean most likely the "Constant On" power section is incorrectly fed.

Remove the fuse panel as described on page 12-50 by pulling the spring lever on the left of the fuse block and let it fall down.
Look at the page appropriate for your model 12-65, 12-67 or 12-69. You will see that the fuse block is divided in to 3 sections based on when power is to be applied to each section. 

The interior lights, glove box light and the trunk light are all fed from the same constant power source at the bottom of the fuse block (The factory radio is in the section fed with the key 'on'). Verify that the fuse for "CLK-LTR Body" is being fed from the section with the #10 B/R wire.

If this all looks good then trace the #10 B/R wire to verify that it is connected continuously to the constant source terminal on the starter.

Offline TJ Hopland

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Re: Interior Lights Only Work When Key is Turned - 68 DeVille
« Reply #6 on: December 05, 2017, 08:01:39 PM »
Is it the 3 fusible link from the starter scheme they used in the 70's?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason

Offline Highwayman68

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  • 68 Fleetwood Brougham
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Re: Interior Lights Only Work When Key is Turned - 68 DeVille
« Reply #7 on: December 06, 2017, 10:57:20 AM »
Is it the 3 fusible link from the starter scheme they used in the 70's?

Yes, there is a 18DG and two 16B wires connected to the Starter.