Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello & Welcome,
Are you saying that the low beams do not work at all when the headlights are turned on (manually)?
Below is the schematic for this part of the system.
I would suspect the Turn Signal/Headlight Switch, which I have highlighted above.
I would also want to verify that it is bad by putting a jumper between the input of that switch (Pin 19 of connector C216) and the output pin of that same connector (Pin 13 for low beam, Pin 20 for High beam). You will notice that there is a separate ground line that comes in when you hold the switch back (the Pass setting), so you could also just try a jumper from a good ground point to Pin 19 of that connector, when the headlight switch is ON. Here is the other part of the schematic that shows how the Headlamp Relay is used.
I hope this helps. Please let me know what you find.
Take Care, Greg A.
In your first message you said that the DRLs do work.
Now you say the DRLs do not work.
Which is correct?
OK - Thanks.
I just wanted to get that straight. So when the DRLs are on, the headlights are ON at a reduced level - correct? You have verfied that the low beam lamps are actually ON during the day?
I only ask because sometimes there is an indicator on the dash for DRL operation, but the lights are not actually on.
One other thing - Do you have a test light or multimeter you can use to do some testing?
OK - Good.
How do you keep the DRLs on at night if the light sensor turns them off (just curious)?
OK - Thanks.
Please let me know when you get a chance to test that switch, and we can go from there.
I also wanted to send along the circuit description for Headlights & DRL system. This might help explaing the sytem a little better.
The daytime running lamps (DRL) control module and the turn signal/headlamp switch control the headlamps. The H/L, L and H/L, R Fuses supply voltage to the headlamps, the high beam indicator and the headlamp relay through the DRL diode at all times.
With the switch in the HEAD position and the dimmer switch in low, ground is provided to the low beam filaments through the dimmer switch and the closed contacts of the Headlamp Relay to G200. The low beam filaments will light when the ground is supplied.
With the dimmer switch in the high position, the high beam filaments in the headlamps ground through the dimmer switch, through the closed contacts of the headlamp relay to G200. The high beam filaments will light when the ground is supplied. The ground path for the high beam Indicator is the same as the high beam filaments.
With the dimmer switch in the pass position, the high beam filaments in the headlamps ground through the dimmer switch to G200. The high beam filaments will light with ground supplied. The ground path for the high beam Indicator is the same as the high beam filaments.
The ON or START position of the ignition switch applies voltage to the DRL control module through the IG Fuse. The DRL control module permanently grounds to G200. The following conditions are required before the DRL system will work properly:
When the parking brake engages, the parking brake switch closes. The switch provides a ground to the DRL control module. The ground disables the DRL operation. When the generator is not operating, a switch in the generator closes. The switch provides a ground to the DRL control module. The ground disables the DRL operation. When the turn signal/headlamp switch is in the HEAD position, a ground is provided to the DRL control module. This signal disables DRL operation.
When all of the conditions for DRL operation are met, the DRL control module provides a ground for the low beam filaments in the headlamps through the DRL control module to G200. The H/L, L and H/L, R Fuses supply the voltage to the headlamps at all times. The low beam filaments will light at 80 percent intensity.
The ON position of the ignition switch applies voltage to the ambient light sensor through the DEF Fuse. The ambient light sensor permanently grounds to G200. When the ambient light sensor senses a low light condition, a path to ground is provided to the headlamp relay through the ambient light sensor. This same signal is also provided to the DRL control module and disables DRL operation. Voltage is provided from the H/L Fuses, through the DRL diode to the coil of the headlamp relay. The relay contacts close providing a ground to the headlamps. The headlamps will light at full intensity.
Please let me know what you find.
Take Care, Greg A.
It does sound like we are making progress and I kind of like it that the dimmer switch is not bad, as those can be hard to change sometimes.
What I would do is double-check that you have the right relay for the headlight relay. Then I would test to see if you can make it operate properly. You might need some help with the switching, but you should be able to turn the manual headlight switch to the headlight setting and hear (and feel) the relay turning ON and OFF when the switch is used.
You could also pull that relay out and test to see if you are seeing the right conditions for the headlight relay to be closing. That is, ground from the headlamp switch, and power from the DRL diode.
Please let me know what you find or if you need more information.
Thanks for the accept and for letting me know what the issue was.
Good Job in finding and fixing it!