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2001 Silverado Headlights don't work !!!

05-06-2004, 07:51 PM
I am new on trucks and I would like some help to fix it.
The headlights and the license lights do not work.
The higth beams are working ok and my DLR, too.
I heard the switch when DLR are working at sunset but the headlights don't turn on neither with the rotary switch on my dashboard.
Thanks for the step by step procedure.

05-07-2004, 04:21 AM
check the bulbs, fuses, and wiring at the headlamps. Someone may have used aftermarket bulbs and toasted any or all of the above.

05-07-2004, 01:55 PM
I already checked the fuses and bulbs.They are ok.
I don't know how to check the wires from under hood (driver side) electrical center at the headlamps and from rotary switch to fuse box.
I don't know what color wires to look for.Is a simple wiring routing? Is a fusible link in-line with the headlamps? Is these ligths computer control?If I fix this problem,I will solve the license plate ligths,too?
Or is different approach to do it.
Thank for your helping hands !!!

05-10-2004, 06:12 PM
Does anyone have the any hint for my truck problem?
Anyone know who sell the electrical wiring manual ,service manual for this truck at fair price.Helm's is so pricey
Thanks !!

05-10-2004, 08:23 PM
helm's is expencive because they are complete dealer manuals, you can join alldata or ask a local garage if they can plrint a scematic for you. your licence plate lights are wired with you rear runnind lights if your running lights work then it is a bulb a corroded socket or a broken wire . the wire color for rear licence and running is brown for Lh side brown/white for Rh powers black are ground. check and see if someone wired up a trailer connector if they sliced into the wires they may have corroded. as for the lo beams they are grounded through the dimmer switch in the steering colum which is part of the multi function switch which should be a yellow wire running to the connector if you ground this wire the low beams should come on. if they do you need a new multifunction switch. sometimes you can manualy turn on the headlight and have a friend watch the headlights while you jiggle the switch to see if they flicker. from what you discribe i am think it is the switch if your high beams and drl's are working ok. good luck

05-12-2004, 07:11 PM
Is there a fusible link between headlamps and switch?
Someone can describe the routing of the wiring from switch to HLamls?

05-13-2004, 01:35 AM
I have a 99/01 CHILTON manual!
Here is a simple brake down on how your headlamps work, starting with the B+ and working our way to B- (battery + & - voltage)

(a) B+ begins at a relay under the hood and is energized by either the (ambient light sensor) or the (headlamp and dimmer switch)

(b) The relay supplies power for both the High and low beams Via a left and right 15A fuse through "A" single wire.

sense your high beams work you can discount, both a & b above.

(c) left and right headlamp low beams have a single "-" negative ground wire (Yellow) all the way to your (Dimmer switch).

(d) left and right headlamp high beams have a single "-" negative ground wire (purple) all the way to your (Dimmer switch).

sense your high beams work you can discount (d) but (c) is a possibility.

(e) once the wires reach the dimmer switch, you will select what ground (high) or (low) beam you want to use.

(f) the dimmer switch has a common ground (black) for all the above functions.

sense your high beams work you can discount (f) but (e) is a possibility.

To finalize, I think you either have a bad wire or connector between the dimmer switch and headlamps, or a bad switch it-self

good luck


05-13-2004, 03:29 PM
So, I can say there is not a wire between ambient light sensor to dimmer switch and low beams headlamps? If I have a bad switch, the sensor will turn on my low beams, Am I rigth? Is this the way the sensor work?
Thanks to all for the reply!!!

05-14-2004, 12:49 AM
The ambient light sensor energize's the headlight relay and provides power for both high and low beams.

The head-light/dimmer switch bypass's the light sensor, so you can force either high or low beams to aluminate.

Your problem in a nut shell is you lost the (ground B-) to the low beams.

To test my hypothesis locate the low beam (yellow) wire right at the headlamp connector.

Turn on your headlights with the head-light/dimmer switch.
Ground the yellow wire to the truck, and the Low beams should come on!


05-18-2004, 02:37 PM
Thanks,Mike. Your hypothesis was right !!
I ground the yellow wire and the headlamps work.
Unfortunately,I was enable to fix it .
I traced the yellow wire from headlamps and the wire ended underneath the "underhood electrical center"(fuse/relay block).I removed the screw to release the socket and the wire has spade terminal without exit at the top. I am puzzled with this design!!!
Also, I disassembled the dimmer switch (springs,ball bearing,contacts) and it looks OK; but I didn't find the yellow wire here.

These are the color wiring for the dimmer switch:
Green,purple,blue/white,black,orange,white,orange,light blue.

Color wiring for headlamps socket:
Low beams:Yellow and orange.
Hight beams: purple and orange.

Does someone knows where are come from/going to these wire?
I would like to fix correctly or any suggestion where to ground the yellow wire?

05-22-2004, 12:39 AM
Are these wires able to handle motor heat?
The jackets look so cheap that I think they are easy to get "open"(when melt down)

05-22-2004, 06:16 PM
the wire colors you listed are from the headlight switch on the dash you want to check the switch on the colum below the steering wheel the one you use to change from high to low also used for signals,wipers and cruise control, (not the one you use to turn on the lights,) which inless you have a broken wire i am pretty sure is your ploblem, you can check by groundind yellow wire on the connector at bottom of steering column look for wires comming down and out of colum.
yes the wires can handle motor heat inless they are very close or right against the exhuast.

05-25-2004, 11:36 PM
Sorry I didn't get back sooner.
Follow mjgjr72's advise, and locate the yellow wire @ the stearing collum and follow it to the nearest connector.
Do you have a an Ohm meter?


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