My high and low beams were off, then i cleaned the corrosion off the connector of the battery and now the high beams work...low beams still do not! 2005 hyundai sonata

Headlamps
The headlamps are operated when the driver places the headlamp switch in the HEADLAMP position. The LT HDLP and RT HDLP fuse in the IP fuse block, supply battery positive voltage to both the left and right headlamps. The low beam and high beam circuits continue to the headlamp switch. Depending on the position of the dimmer switch, either the low or high beam circuit will now have a path to ground. Ground is provided at G204. The low beam and high beam circuits also provide the body control module (BCM) with both low and high beam inputs. The headlamp switch includes the dimmer and the flash-to-pass switch.
If the headlight switch is left in the HEADLAMP position, the headlights will remain on until turned off or the battery runs dead.

The ground under the battery has nothing to do with the headlamps . G-204
G204
On the steering column support bracket

Just the low beams not working ??????
Headlamps Inoperative - Low Beams
Step
Action
Yes
No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
1
Did you perform the Lighting System Diagnostic System Check?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Lighting Systems
2
Place the headlamp switch in the HEADLAMP position.
Place the headlamp dimmer switch in the LOW position.
Do the low beam headlamps illuminate?
YES - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
NO - Go to Step 3
3
Inspect for poor connections at the harness connector of the headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 5
NO - Go to Step 4
4
Replace the headlamp switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column.
YES - Did you complete the replacement?
NO - Go to Step 5
--
5
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3

Basic Electricity for Service Techs Ohm law Current Flow Opens Shorts
Electric Testing Techniques You Need to Know

Learn how to test the electrical circuit's properly . Using a DVOM - digital volt ohm meter . An get yourself good factory service repair manual ,don't guess an think you know how to fix it.

try checking the connector. It is pretty common for the spade lugs that connect get corroded. Make sure there is no corrosion or clean them off and squeeze then together a little to make the connection tighter. If that does not help, verify if the high beam works or if the problem is only the LOW beam. If you have handy a multimeter, check for +12V on that connectors.

Check connector may be bent.

Check the socket for corrosion. If there is some clean it up and see if the light works. If there is no corrosion or if the light still doesn't work after cleaning the socket then test the low beam circuit for power. If there is no power consult an auto electric shop or the dealer.

You have a bad electrical connection. Check the wiring harness and both sides of it's connectors for corrosion and or breakage. The connector terminals will become worn and corroded and the wiring sheaths a prone to weathering and become brittle. Replace or clean as needed.

From under the car below the battery box, check the harness near the connector for signs of corrosion. If you see green on the wires they've been exposed to run off from the battery and will need to be repaired by solidering in new wire.

Make sure the connection at the lamp is clean and corrosion free. If corroded, clean with an electrical contact cleaner or baking soda and water then retest. Check the high-beam operation. If the light works on high-beam then you have a wiring problem on the low-beam power circuit. If neither the high nor the low-beam works then you likely have a ground circuit problem. Check the pins at the lamp connector using a Digital Volt/Ohm Meter and the appropriate wiring diagram. Voltage should be within 0.5 volts of battery voltage. Resistance to ground should be less than 5 Ohms with the ignition key off. These tests will give you a better idea as to which circuit is faulty.

Check the Pink wire for high beams and the Dark Blue wire for low beams. Common locations for wiring problems are behind the headlights, under the battery tray. Check for a corroded wiring harness connector or wires at this location. If the wires or connections are found to be corroded, repair or replace the wire or connector as necessary.

Several things on your cavalier could cause this to happen...
If it's just your high-beams, low-beams, or DRL that are out (just one), start with the DRL relay (in the fuse box). If that's not it, and it's not the DRL, try the multi-function switch (the thing attached to the left of your steering wheel, the headlight switch/cruise control switch). If all that checks out ok the next place to look under the hood... there is a pin-out connector/harness under the battery box (located in the front on the driver's side) that may be corroded. It is attached to the underside, and not easy to see without a mirror. If there is corrosion on the battery box, this connector is probably corroded as well...anything that runs off the battery will find it's way to this connector.

Note for anyone else that reads this: Different people will experience similar problems, sometimes with the low-beams, sometimes with the highs, because of different corrosion patterns and the DRLs being run from different bulbs.
Good luck...i hope this helps, please take time to rate me a fixya.

Hi,

Since it is only the left low that is the concern, then probable faults are:

• bulb (low filament) replace if necessary;
• loose wiring connection (either the wire itself or the connector). Try wiggling the wiring/connector. In some instances, you may need to scrape the lugs/pins to clean any corrosion or burnt marks.
  

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.