No headlights Chevrolet Prizm
This article is No headlights Chevrolet Prizm
In the good old days you’d turn on the headlights and the lights would go on. If they didn’t, you could follow the power from the fuse box, through the headlight switch and then to the headlights. Well, those days are gone forever. Now, instead of actually switching power to the headlights, the headlight switch is used to signal the daytime running lamps module (DRL) which controls the headlights.
Power runs from the gauge fuse to the DRL. Power runs from the main fuse (40A) to the headlight relay contacts and control coil. The DRL runs power to the headlight switch on the light green/black, red/white wire, and red/yellow wires. When you flip the switch to parking lamps, the switch connects the light green/black wire to the ground located in the right kick panel. When you flip the switch to parking lamps, the switch connects the red/white wire to the ground located in the right kick panel. When you flip the switch to high beams, the switch connects the light red/yellow wire to the ground located in the right kick panel. When the DRL sees power drop to ground on those wires, that’s the signal to provide ground to the control circuit on the headlight, high beam, or tail-lamp relays.
From the headlight relay, power flows to the dimmer relay contact and control coil circuits. In the low beam (default) mode) power flows through the dimmer relay contacts to left hand and right hand fuses and then to the low beam filaments in the bulbs. To get ground, power must flow from the bulb filaments to the DRL relay and then to the ground connection behind the battery. The default position of the DRL relay is OFF. So the control circuit of the DRL relay must receive power from the DRL fuse (7.5A) and ground from the DRL control module.
So you can see there are multiple points of failure here. Start by turning on the headlight switch (parking brake OFF) and starting the engine. Then pull the DRL relay and check for power (from the headlights) on terminal 2 in the DRL socket. If you get power, then power is getting to the headlights, through the filament and is just looking for ground. In that case, test DRL socket terminal 3 for power (from the DRL fuse). If that’s good, check DRL socket terminal 1 for ground from the DRL module. If you’re not getting ground, you’ve got a bad DRL module, bad headlight switch, or a wiring problem.
If you’re NOT getting power on terminal 2, get a wiring diagram and work your way back through the dimmer relay and headlight switches.
© 2012 Rick MuscoplatPosted on by Rick Muscoplat