Headlights, park lights, taillights, dash lights, interior lights all suddenly stopped working

HMON4067

MEMBER
1978 CHEVROLET MONTE CARLO
5.0L
V8
2WD
AUTOMATIC
176,000 MILES

We bought this car new! Found that the headlights, park lights, taillights, dash lights, interior lights are suddenly not working? Brake lights, turn signals are working. There are no blown fuses? I am leaning toward a headlight switch? I put a new one in about 35 years ago! Do you know of any additional tests I could perform? I appreciate any help you could give me.
Thank you,
Harold L Montgomery

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi,

Harold, I have to agree with your diagnosis. On these vehicles, there aren't a lot of other things that can cause this. I would tell you to check grounds, but several of the things you have not working have different grounds from each other.

Try the switch and let me know if that takes care of it.

Joe

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Wednesday, February 19th, 2020 AT 4:10 PM

HMON4067

MEMBER
3 POSTS

I installed a new headlight switch. No change. I found a fusible link at the starter bad.
Repaired the link. Headlights, Park, Taillights work! Interior lights, dome and clock not
working? Any ideas?
Thanks

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Monday, March 30th, 2020 AT 1:56 PM

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

I just tried to find a schematic and don't have access to one. Most likely, it's because of the year. Now I can tell that you are very competent. So, what I would suggest is to simply start by checking fuses. In addition to the fuses, confirm there is power available to the fuse. Next, (and without a schematic I can't be specific), confirm the dimmer on the switch has power. With what you have already done, I suspect you have checked bulbs. Also, is the clock on this part of the radio or is it a separate component?

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Monday, March 30th, 2020 AT 7:37 PM