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Headlights NOT on

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Old 07-27-2004, 09:03 AM
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Originally Posted by mySStery_machine
I just got off the phone with Chevy and they are saying the module that I found last night behind the stereo is the DRL/headlight module. They also informed me that to the right of this behind the glove box area is the three relays that I need to get to. The relay in the middle is the winner according to them...this sound right to all people? The other relays they said are sensors for theft and something else ( I can't remember).
No, as you can see from the diagram, the headlamp and parking lamp relays are internal to the DRL module (broken line surrounding the relays in the diagram). Checking the service manual component locator page shows a theft deterrent relay behind the dash but no separate light relays.
Old 07-27-2004, 09:31 AM
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So then I need to open that module I found last night and just replace that one relay? Thanks for the help WhiteBird got a copy you can shoot me of the other stuff you were looking at?
Old 07-27-2004, 09:32 AM
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Originally Posted by WhiteBird00
No, as you can see from the diagram, the headlamp and parking lamp relays are internal to the DRL module (broken line surrounding the relays in the diagram). Checking the service manual component locator page shows a theft deterrent relay behind the dash but no separate light relays.

He's right, the starter disable relay is located to the right of the glovebox opening above the BCM, however, no headlight relays there.
Old 07-27-2004, 09:42 AM
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Originally Posted by mySStery_machine
So then I need to open that module I found last night and just replace that one relay? Thanks for the help WhiteBird got a copy you can shoot me of the other stuff you were looking at?
Well, you can open up the DRL module and see if the relay is replaceable. I'm sure that GM doesn't sell it separately (they'll sell you the whole module) but you might find a generic pc-board relay that will work.

Sorry, the manual is in web page format so it would be very difficult to post. You can get the service manual CDs on ebay for around $40. They cover all GM models from 98-up as well as service bulletins and other info for earlier models.
Old 07-27-2004, 10:30 AM
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See the part numbers I got off of the module I found last night was 10407669 and that comes back via GM as a DRL/headlight module. The parts section today came back as 12177233 being the actual relay. Any confirmation? DRL module is over $100 and relay is about $30.
Old 07-27-2004, 10:40 AM
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My parts list shows 10407669 as the correct number for the DRL module. However, 12177233 is listed as the rear hatch release relay. It is mounted near the DRL module next to the theft deterrent relay (which is part number 12103601). The parts list doesn't show any internal parts of the DRL module being sold separately - just the module as an assembly.
Old 07-27-2004, 10:53 AM
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OK so then the whole thing has to go then I guess...dammit! So one relay inside is good for parking and power sending to fogs...and one is crap. The parking dimming as headlights would be going on is a good thing then I would guess correct? This shows that at least SOME of it is working.
Old 07-27-2004, 10:58 AM
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Yes, there are two internal relays - one for headlights and the other for parking lights. The fog lights use a different relay which is under the hood in junction box #1. The front lights dimming is proper operation - they should be on full bright as daytime running lights and then dim to running/parking lights when the headlights are turned on.
Old 07-27-2004, 12:31 PM
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OK so my original assessment from two weeks ago was correct, it needing a new relay now I need to locate the part from a salvage yard so it won't cost so damn much...maybe ebay. Thank you for all the help. Hopefully I will have one in so I can get to the track Thurs, it's been killing me not able to leave past dark in my car, especially since we moved to within 5 mins of the local track and what sweet music every Thurs and Sat.
Old 07-27-2004, 01:12 PM
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Just found it for only $25 over at a salvage yard, the guy needed to know where to find it and then said 'Uhh $25 sound good?' Guess I found a winner, it's from a 99 too so not too bad there.
Old 08-01-2004, 08:01 AM
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WHITEBIRD or anyone electronic savvy I have changed out the DRL module and still no headlights are working. Could it be the relay in the parking brake area? I was thinking it may be somehow linked since it I was using the bypass to get the original problem of headlights coming on instead of the DRLs, and then just turning the headlights on when needed at night.
Old 08-02-2004, 08:42 AM
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OK, lets start with some testing to see if we can narrow down the source. Best place to start is at the headlight switch. You can get at the connections by removing the trim plate and the two bolts that hold the switch in place, then pulling the switch out of the dash.

First, check that you have 12V at both red wires. One is the 12V battery feed which comes from a fusible link which is under the hood on the left inner fender. The other is the output to the DRL module. Both should show 12V+ at all times. If neither does then check the fusible link. If one does but the other doesn't then replace the switch. (Note: you will also have 12V+ at the orange wire but that is the feed for the parking/running/fog lamps and you said that they still work.)

Now that we've established power, let's check output. Connect a test light from the yellow wire to a ground. With the switch OFF or in the PARK position there should be no power on the yellow wire. When you move the switch to the HEADLIGHT position the yellow wire should have power. If not, replace the switch. Another way would be to place a jumper wire between the red power supply and the yellow output wire to see if bypassing the switch gets the lights working. Just be careful because that would be a high-current connection.

The next step is to test the headlight dimmer switch. You will find a 3-pin connector near the bottom of the steering column on the left side that has yellow, tan and light green wires. First check that the yellow wire has power when the headlight switch is on. If not, find where the yellow wire is broken between the headlight switch and the dimmer switch. Then check that the tan wire has power in the low beam position and the light green wire has power in the high beam position. If not, replace the dimmer switch.

From there, the wires just run through the big grommet on the left side of the firewall to the headlights and then to separate left and right grounds. I am assuming that it's unlikely that all the bulbs would have burned out at once or that both side ground connections would go bad at the same time. If everything else checks out, check for power on the tan (low beam) and light green (high beam) wires at the headlights then trace back to find any break in the wires.
Old 08-05-2004, 11:30 AM
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This really helped a lot Whitebird the only thing that I cannot figure out and nor can the electronics guru I have helping me is, where the hell is this fusable link you speak of? I have been under the hood and looking all over but can't find what you are talking about. I see all the connections over behing the battery towards the ECM but see nothing like I think you may be talking about. Another type of schematic or really copious directions would be great.
Old 08-05-2004, 11:45 AM
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According to the service manual, the fusible links (there are two) are located "Forward of the left front wheelhouse, behind the underhood electrical center #2". They are black in color and are both connected to a heavy gauge red wire from the "Engine Wiring Harness Junction Block #1" at one end. The other ends both are connected to smaller red wires - one goes to the headlight switch and the other goes to the BCM.

I hope this helps because the manual doesn't have any pictures or diagrams of these fusible links that I could post.
Old 08-06-2004, 06:15 AM
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OK so that would mean left as in driver side, I wasn't sure if it was left looking at the car or left once in the car. Those must be the 'open' links under the lid in the engine fuse area. Does this sound about right?
Old 08-06-2004, 07:32 AM
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Yes, parts and service manuals always refer to left and right from the driver's position. There are two electrical junction boxes on the left (driver's side) fender well. There are three fusible links bundled together below the heavy cable that attaches to the red covered stud on the rearward box. They are short pieces of wire with black insulation that has a broken white line running along them.
Old 08-06-2004, 03:46 PM
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OK so I went along and checked all output numbers and this is what I came up with. I have power at port J behind the switch but not at G. The yellow has no power EVER either at the switch or the 3 point juncture. Remember now that when I bought a new switch al while ago that it just smoked out and for the most part died. I luckily did that at the salvage yard and just told them sorry but apparently that wasnt what I needed. I am no longer getting the 4th of July sparks though from bridging directly from J to the yellow so maybe a new switch is in order now? There is another yard in the area that has one available. What say you?
Old 08-07-2004, 02:18 PM
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Power at pin J would mean that the fusible link is OK. That's your main power supply to the switch. If you have no output power at pin G (DRL module output) then the switch itself is fried. There appears to be some kind of internal fuse or fusible link inside the switch (according to the diagram) but it doesn't seem to be replaceable according to the manual. That internal fuse would also keep power from reaching pin E (the yellow wire feeding the lights).

Replacing the switch will be necessary but I'm concerned that whatever caused it to burn up in the first place may still be a problem. Try checking the wires at both E and G with a meter for any short to ground that might have caused the original problem.
Old 08-07-2004, 02:56 PM
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Hey Whitebird do you have PayPal? I need to sent you some $$$ so I can at least buy you a beer for all the help. I was thinking a grounding prob over near the new battery I put in could be a problem, might it be a ground near the handbrake since I used that to bypass the orig prob for so long? Just things I think about while sitting around at night (since I can go out) and drinking.

As a side note how would I be checking exactly for this bad ground? The stupid gene has stuck me down once again.

OK yellow E is checking in with a whopping 0.0 and the 2nd red G is coming in with a huge 0.09, that's about it lead the way. Oh and grounds at the battery are good into the harness.

Last edited by mySStery_machine; 08-07-2004 at 03:07 PM.
Old 08-07-2004, 08:09 PM
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What you want to look for is either the E or G pins being shorted to ground someplace (worn insulation on the wire or whatever). You do this with a multimeter set to ohms. Touch the red meter probe to the switch pin and the black to a known good ground like a bolt under the dash. The meter should not show any number close to zero. The reading will change somewhat because the circuits are connected indirectly to ground but it shouldn't be close to zero (for example, the yellow wire goes through the headlight bulb to ground so the filament prvides resistance). If it does show zero then you'll have to follow that wire until you find where it's grounding out.

Thanks for the offer but I couldn't take money from someone who also lives in Jacksonville (even if in another state).


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