Headlights will not turn on

2002 CADILLAC DEVILLE
200,000 MILES • V8 • 2WD • AUTOMATIC
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KNIELSEN84
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The fuses are all good and relays are all good, but the parking lights come on?
Jan 29, 2021 at 6:32 PM
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DANNY L
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Hello, I'm Danny.

It sounds like you might be having an issue with the headlight low beam relay. Here is a tutorial showing how to test a relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

I've attached a picture of the under hood fuse block which houses the low beam relay in location #28. I've circled it in red. If you want to try this, Switch the high beam relay in location #27 below it and see if the low beams come on. That will let you know if the relay is bad or you have an electrical wiring problem. Let us know what you find out. Hope this helps and thanks for using 2CarPros.
Jan 29, 2021 at 11:28 PM
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KNIELSEN84
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No, sorry that doesn't work.
Jan 30, 2021 at 8:12 AM
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KASEKENNY
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Just to clarify what the issue is that you are dealing with, when you turn the head lights on, they do not come on but the parking lights do come on?

Do the high beams work? Either when you have the lights on and you turn the high beams on or the flash to pass?

I would suggest starting with checking the signal from the switch to the relay. The last attachment below shows a close up on this wire from the switch to the relay. We need to test this by removing the relay and putting your red meter lead on battery positive and the black lead on the terminal of this wire and turn the headlights on. You should have 12 volts on the meter as the switch grounds this circuit to close the relay and that sends voltage to the headlights.

Let's run through this and see what turns up. Thanks
Feb 2, 2021 at 3:34 PM
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KNIELSEN84
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Okay, get back to you. thanks
Feb 2, 2021 at 7:35 PM
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DANNY L
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Hello again.

Just curious to know if you made any progress with wire testing. Let us know if you need anything else. Hope this helps and thanks again for using 2CarPros.

Danny-
Feb 5, 2021 at 9:24 PM