1 Dim headlight and lots of questions - Toyota Nation Forum : Toyota Car and Truck Forums

Brann · 02-14-2010, 10:01 AM

I have a 95 Corolla DX with an odd electrical problem that is confusing the hell out of me.

Issue:

The passenger side headlight is VERY dim while the driver side headlight functions 100% fine. When you turn the high beams on the passenger side shuts off both bulbs and the drivers side works 100% fine again.

What I have tried:

The battery terminals were replaced and the battery was cleaned. Both passenger side hight and low beam bulbs where replaced. The only effect this has had on the problem is my wallet is getting thiner

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I have now idea what could be causing this to happen to only one side of the car and after being pulled over by the cops twice and with the inspection sticker being up in a month this is turning into a big issue. I have basic electrical tools like a multimeter and would be very thankful if anyone could give me some more troubleshooting ideas since I am anything BUT a car guy.

Thanks in advance

gold94corolla · 02-14-2010, 10:50 AM

Maybe you need new wiring or connectors.

Brann · 02-14-2010, 11:02 AM

There is no chance it could be a relay or a switch issue right? I had a friend of mine bring that up, but I kind of dismissed it. I assumed if it was a relay or switch problem it would effect both headlights and not just the one... Right?

Bitter · 02-14-2010, 11:11 AM

its probably a burned terminal or a bad ground at that one headlight, you'll need a wiring diagram to tell which wire is ground for that side and then just splice onto it and create a new ground. that sounds like it may cure the issue...if it does not then its likely a power feed issue and you'll need to chase down where theres a bad spot in the wiring or just run a few new wires.

Brann · 02-14-2010, 11:21 AM

I have found diagrams for a bunch of other models other than the 95... You or anyone else would not happen to know of a legit place to find a good diagram would you?

Bitter · 02-14-2010, 01:15 PM

they probably are the same wire colors, why not just go and check?

Hook · 02-14-2010, 06:27 PM

First off, check for any burnt or broken wires, because on H4 bulbs, the low beam cuts out when the high beam kicks in, so it appears you're not getting any high beam power on that side (verify this with the multimeter).
Also, sometimes the spade connectors inside the socket get bent open when replacing bulbs and doesn't make proper contact, so eliminate this possibility early on before u move on. A loose terminal sparks and becomes sooty, which prevents it from making proper electrical contact with the bulb pins. At worst, it becomes hot from all the sparking and can melt the wire conductors inside of the sheath (making an apparently good wire with bad conductors inside) or terminate the wire completely (you'll see where it either bubbles the insulation or burns it completely).
Provided the wires are fine, you can clean the connector with contact cleaner spray and use a precision screwdriver to bend the ends of the spade connectors back in if this is the case, but personally for a 15y/o car, I'd replace the entire socket.

If physically the wiring and socket checks out fine and the ground is fine then you'll need to trace back the wires along the harness to the source and checking for continuity and that the headlight relays are fine.

Brann · 02-14-2010, 07:29 PM

Thank you for the detailed reply. I will go out replace the socket tomorrow since it does look a little beat up. I could not really spot any damage to the connectors inside the socket itself, but I could of missed something... For the price of a new socket I might as well just remove that from the pile of would be problems.

I will post back with my results

speedy25 · 02-14-2010, 09:26 PM

The REASON for the dim headlight is a bad ground. Search the wiring for where the common connection is made. It could be on the bulb connection or more typically the connection where it attaches to the body is rusted or broken.

-SP

Hook · 02-14-2010, 10:32 PM

Yeah, hopefully it's as simple as a bad ground connection on the socket itself. I just put a little more into it because the possibility exits it could be other faults in the circuit or multiple problems.

It's best to start with the simple stuff first. Start with a physical inspection and check for proper voltages, grounds, then continuity in the wires, then start checking more complex components.