My chevy impala 2002 headlights wont turn on. I changed the headlamp relay and still nothing. My brights, dashlights work, corner lights, taillights and brakes work, but no headlights. What should i do now?

Check headlamp fuses and relay.

You replaced the headlight switch? Then check for a fusible link or a maxi-fuse that supplies power to the light switch.

If the relay were the problem both sides wouldn't work . Do you know how to do automotive electrical testing ? How to read a wiring diagram ? You can view wiring diagrams here http://www.bbbind.com/free_tsb.html Enter your vehicle info. year , make , model , engine size . Then under system click on lighting , then subsystem click headlamps . Click on the search button , then on the blue links one at a time . At the top of the first diagram you will see the fuse's for low an high beams . The fuse's send B+ voltage directly to the high an low beams , from there B+ voltage goes on to the dimmer switch shown on the next diagram .Low beam headlamps from the dimmer swich goes through the headlamp relay when energized by the BCM . When the relay is energized that compleats the circuit to ground at G- 201 . So you see if one side is working it can't be the relay . Doing electrical testing , voltage drop testing is the way to find the problem .
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GOOD ADVISE--I ALSO LEARNED THAT THERE MAY BE FUSES IN UNDER THE HOOD ALSO. FOUND OUT TODAY THAT IF THE DOME LIGHT DON'T WORK THEN IT'S FUSE COULD BE BLOWN AND HINDER THE CIRCUIT TOO. I'M NOT GOOD ON VOLTAGE READING , BUT DO HAVE A TEST LIGHT. IF NO FIRE AT THE COMMON TAIL LIGT-DASH LIGHT FUSE , THEN THAT MIGHT NARROW IT DOWN. I HAD THE SAME TROUBLE IN MY 1990 FORD XLT LARIAT AND WAS BLOWING THE TAILLIGHT FUSE. IT WAS A SHORT IN THE EXTERNAL TRAILER KIT HARNESS WHICH CAUSED FUSES TO BLOW REGUARLY. WHERE IS RELAY FOR TAILIGHTS AND OTHER FUSES UNDER THE HOOD??

Okay, these are hard to find. I assume you have no problem when you do not have the Tailights on? This would mean problem could run all the way to rear taillights.

But if the problem is not related to putting power through the wires to the taillights it is under the dash area. You would have a short from the power supply to the lightswitch. You have a Relay for the lights in the Powerbox.

Go to Autozone.com Website and register your vehicle for a free wiring diagram and Powerbox layout.

You can then see for yourself about how the dashlights are grouped with the taillights. You could have a bad Relay.

Look at how the taillights get their power and this will show you a color/coded path from the front to rear of your car. As I said earlier, it is important to know if the lights only short when they are turned on by the headlight switch.

If they short out all the time, regardless of the headlight switch being on or off, then the short is more towards the front, between the dash and Relay or the Relay itself.

Use the built-in cutoff points as a way of eliminating the shorted part. The headlight switch is a cutoff point. Power rearward is halted with the except of the Brakelights. If the Brakelights work fine, the bulb sockets are probably grounded properly.

If the fuse pops with the headlamps off, the power is not going rearward and you are okay.

There are two "dimmers".. The first is used to switch between high and low beam healamps. This switch is integrated into the "smartswitch" which contains the turn signals as well. The other dimmer switch is for the dashboard lamps and allows you to adjust the brightness of the dashlights. This is part of the the headlamp switch assembly.This is a common failure item in impalas and when it fails it usually results in loss of dashboard lamps when driving at night. Replacement of the headlamp switch is necessary.

If you are 100% sure the lights are ok, it's going to either be the headlamp relay or the high/low switch. I'd swap a bulb for a new one before moving on to more troubleshooting.

Hope this helps.

yes sounds like the switch went bad or haves a short in the wiring

if you have auto lights it could be the photo eye or its the headlight switch

Check headlight and high beam switch for power in, power out. If power there, change whichever switch isn't working (remember dimmer switch gets power from headlamp switch) If no power going to headlamp switch check main fuses and fusable links for problems.