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Topic: 1978 Interior lights not working

in Forum: C3 Electrical


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1978 Interior lights not working (1/6)
 10/1/24 8:08am
rigal02
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HARRISBURG, PA - USA

Vette(s):
1978 Silver Anniversary


Joined: 9/12/2024
Posts: 3

I have a recently purchased 1978, late year build date, that the interior lights don't work. The headlight switch turned counterclockwise does not turn them on. No power at either of the door switches. If i ground the bulb in each of the three lights, they light. Glove box light works, radio works, and dash lights work and dim with headlight switch. I was told that the timer was replaced and they were working prior to me purchasing. Is there a test procedure for the timer? What else might I check? Thank you!

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Re: 1978 Interior lights not working (2/6)
 10/1/24 1:20pm
Kentvetteuk
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, - France

Vette(s):
1978 L48 Auto. Red with Oyster Leather interior. Owned since 1990.


Joined: 8/21/2002
Posts: 115

You may be able to get an idea of what to look for from these (not great!) photos of the Electrical Troubleshooting Manual.

At a quick glance you could check the two fuses mentioned, the CLK LTR CRTSY and the GAUGES fuse, both of which seem to be good for the timer to work.   

Based on and experience I had it will be worth checking that the timer unit is fully plugged in!

 

 

 



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Stephen J Irons
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Re: 1978 Interior lights not working (3/6)
 10/1/24 9:33pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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rigal02 said:

...... If i ground the bulb in each of the three lights, they light. 


You answered your own question. Check for good ground at the door switches. If you can ground the sockets, and the lamps come on, then you have power to them....you must have a ground AT the door switches for the lights to work. The delay timer controls voltage to the sockets, as does the light switch dimmer, but the ground comes from the door switch itself. 😉



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Re: 1978 Interior lights not working (4/6)
 10/2/24 8:26am
rigal02
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HARRISBURG, PA - USA

Vette(s):
1978 Silver Anniversary


Joined: 9/12/2024
Posts: 3

Thank you Kentvettuk for the pics, I'll be able to get back to troubleshooting this weekend.  I'll pull the timer box and recheck the connections.

Re: 1978 Interior lights not working (5/6)
 10/2/24 8:31am
rigal02
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HARRISBURG, PA - USA

Vette(s):
1978 Silver Anniversary


Joined: 9/12/2024
Posts: 3

Thank you Adams' Apple, I did run a test ground to the door switches to check that but possible didn't get through the rust. I ordered two new switches and hopefully will get them before the weekend.  If not I'll pull them out to try to clean them.

Re: 1978 Interior lights not working (6/6)
 10/2/24 9:21am
Kentvetteuk
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, - France

Vette(s):
1978 L48 Auto. Red with Oyster Leather interior. Owned since 1990.


Joined: 8/21/2002
Posts: 115

As you're a relatively new owner of the '78, the Electrical Troubleshooting Manual might be a good purchase😄   There are usually a few decent copies on ebay. 

But in the meantime I came across this on-line version:   https://www.corvettebergen.com/teknisk/1978_corvette_electrical_troubleshooting_manual.pdf

I'm no automotive electrician, but I've found my copy useful for diagnosing a few issues and invaluable when I fitted a new radio and had to unravel "bubba's" work on the radio wiring!😱

Good luck with the car and don't forget, photos are always appreciated!👍



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Stephen J Irons
Corvette Club France
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Corvettes of Southern California
NCM Family Member
Red Corvettes Have More Fun!
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