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Discussion Starter #1
Hello, 1995 Caprice with Twilight Sentinel...I always have the T/S switched off. Headlights low and high do not work all of a sudden. Everything else works. Put in new lamps and the under dash column dimmer switch...Nothing..Does the actual physical headlamp knob switch quit on these? I have not probed anything yet with a tester....Any ideas? Does a bad Sentinel switch kill the headlights even though it is switched off?...Hot as Hades here in Florida so this is a real drag working under the dash now....Thank you much, Uvaldi..
 

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Check headlight switch.. Might not be working. Check other positions to see if you can get the parking lights to come on and such. If I recall, the power for the lights runs through the switch... If you are running bigger wattage bulbs it can burn out your switch..

Rodney
 

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Did you check the fuse?


Throwing parts at it is not always the best way to fix a problem. Do the troubleshooting first, then replace parts. The switch is a good possibility, but check your grounds as well.
 

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Check the relay under the hood, it controls ALL the headlight functions. This is why Gary's harness is a nice upgrade. With Gary's harness his 2 relay harness has one relay that controls low beam and the other controls high beam. His 4 relay uses one relay for each beam function.
 

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Discussion Starter #5
Thanks for the replies...Stock headlights. Dash fuse is good. What should I check on the underhood relay? I am kinda of an electrical idiot..
 

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Discussion Starter #6
Cant seem to find the underhood relay. The fuse box (convenience center) by the A/C dryer does not have one labeled for headlights that I can see...
 

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First grab your FSM or go to Goldswagon and get the headligts/twilight diagram.

Goldswagon diagrams

Headlights low and high do not work all of a sudden. Everything else works.
If your parking lights work you know the fusible link is ok. So the path of power next goes to the headlightsw. In on a red wire constant battery power. The switch sends it out on a yellow wire to the High/Low beam switch on the column.

As the High/Low switch is easier to check I would with the headlight switch on look for 12V at the yellow wire in the H/L beam switch. If it has voltage does the tan and green wire to the headlight have 12V when you move the stalk?

You should not worry about the twilight sentinel at this point. The headlight switch overrides it so you can use the headlights without it. If you have to do a lot of testing I would unplug it until you get the headlights working. The T/S may be confusing if you are working inside or in the dark.

It is unlikely you have a ground problem as each headlight has a separate ground.

If your yellow wire does not have power with the headlightsw on then it is time to take the dash apart and check for power at the red wire.

If you can read my scrawl this is what I used the last time I looked at the headlightsw
 

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Discussion Starter #8
Got your post. Thank you, Took apart dash and want to test the red wire lead to the Headlight switch. It that DC running from that? Have standard Voltmeter. Put red probe on red wire. Where do I touch the black lead from Voltmeter to find if it is 12V? I am a electrical dummy. Thank you, Blake..
 

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Anything with a battery directly connected is DC.

So multimeter set to DC auto range or a range over 15 volts (20?)

If you have a test light it is better for car work.

Red lead to the red wire on the headlight switch. It must not touch anything else. This wire does not have a fuse, if it shorts out it will burn out a hard to replace fusible link.

Black lead needs to go to ground. All the sheet metal in the car is ground, BUT it is covered by paint. The two easy spots to ground to are: The bare metal brace around the fuse holders. Driver's side door open, cover off the fuse panel on the end of the dash. The second easy one is the exposed metal around the cigarette lighter.

If there is about 12 volts on the red wire, repeat the test on the yellow wire with the headlight switch on. If there is power there you will have to check the High/Low beam switch at the bottom of the steering column like I suggested in the last post.

When I get "no headlights" on someone car I start with a spare bulb. I started doing a bulb swap or voltage check at the headlight after someone burnt out all the high and low beams before bring it to me. Wasted hours testing the circuit before I figured out the owner had run the headlight bulbs into the ground.

As with anything on the internet do not do anything you are not sure of.
 

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Just some quick pics.

Testing for voltage output at switch.
You can test the breaker inside the headlight switch by checking for power on the Dark Green wire with white stripe that goes to the twilight module. Wire is not in this 9C1 wire harness.

Testing switch operation with Ohm meter. Near zero ohm when on good.
You can see contact damage on power in and headlight out contacts.
 

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Discussion Starter #12
Ended up being the twilight sentinel module appears to have shorted out the headlamp switch. Put in replacement switch and unplugged the T/S box by the passenger kick panel. Headlights work normal now... It was a real PITA. Mostly from dealing with the brittle lower dash that crumbled on removal and needed to be rebuilt.
 

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.... It was a real PITA. Mostly from dealing with the brittle lower dash that crumbled on removal and needed to be rebuilt.
Every time I have to remove the under panel I'm reminded of a lizard shedding its tail to escape a predator after seeing those tabs left behind. Define 'rebuild' for us. A plastic stick and some plastic epoxy works about 50% of the time for me.
 

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Discussion Starter #14
Yep. Just plastic epoxy...All of the bolt clips just fell out also from the plastic ashtray mounts and the knee panel. Plastic just crumbled. The lower dash panel along with the door panels are truly a terrible design...:frown2:. I am glad the rest of the car is not like that...
 
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