A girl I know has an '01 Sunfire GT, and the passenger headlight has went dim. It's like only half on though the bulb itself is fine.

Her service light also comes on because of this, when the headlights are turned on.

Any help? I have put off fixing this for the longest time.

I had this problem up till today, so I'll tell you about my experience.

You didn't say if the light is dim only when the low beams are on, or if it is dim when the high beams are on too. If this is the case, then your problem lies in the power supply to that headlight. In the case of the passenger side, the problem is the orange wire. The orange wire is only connected to a fuse. A quick way to tell is to use a multimeter and check for continuity between the passenger side headlight fuse and the middle socket on the headlight connector. If this is the case, tthen you're going to want to next check the connector right under the battery. I found it to be a pain to remove. You need to slide both parts of the harness toward the firewall to slide it off it's plastic mount, then there is a gray 'U' shaped piece that you need to pop off. Just use a screwdriver, it should pop right off. You'll need to put a screw driver in the opening to depress the little tab that holds the harness together. Lastly, check for continuity between the wires in that harness and the wires at the light socket. The colors on the light socket are the same as the ones on the harness--Dark Blue, Pink, and Orange if memory serves right.

My problem was in the Orange wire. It was corroded so badly that it broke off as I was inspecting the harness. It corroded part of the pin with it, so I am looking to replace that. I haven't found anyplace that sells just those pins. I'm just running a jumper across the harness till I get my hands on some of those pins.

Some things to look out for:
1)The passenger side headlight is not connected to the DRL relay. If you don't get continuity between the relay and that headlight, don't jump to conclusions and replace the relay.

2)Your problem is not in the switch. I'm almost positive of that. If your problem were in the switch both of your headlights would be dim, or more likely not on at all. The outside pins of both headlight sockets are connected together, then they go to the same two pins on the headlight switch connector.

Sorry this is so long, but I probed a lot of wires and did a lot of testing, so I felt someone should benefit from it.

You're the man. I had a slight feeling it was a bad ground, or wiring fault of some sort. I believe they stay half dim on high and low beams, but I'll double check. Thanks, I'm going to cut off another harness tomorrow and the junkyard and go to town.

I wouldn't go cutting harnesses off just yet. If you can find which wire is the problem, then you can replace JUST THE CORRODED PIN. When you pull the harness apart, you can grab the offending pin with a pair of needle nose pliers and push it out the back of the harness. Then, go to to the dealership and ask for part number 15326268 if it is one of the skinny pins. If it is one of the wider pins ask for 15304730. The list price is about 3 bucks, I think, but the guy at the dealership I went to just gave me two. He had to search for a while to find them, so if they don't know what you are talking about, print this page: 15326268

I have a theory about why the light is still on--dim as it may be. I believe that the difference between the high and low beam voltages in the switch are enough to barely light the bulb.

I grabbed another harness just in case, I'll tackle it in a couple days. Keep me posted with your findings!