Hello, I don’t post here at all so I’m not sure this is the right way to go about this but I’ve been having some issues with my headlights.

I have a 97’ sc300, and just recently only my running lights will come on when I am in the on position, they still work fine when in auto, (I can use my brights and fogs), but they don’t work in regular on.

and just now I hit a bump and my horn wouldn’t stop blaring (it’s working but previous owner didn’t connect it to the wheel), and when it stopped I wasn’t getting the lightbulb on my dash to tell me my lights were on, and now my brights are on at low light, while my right headlight won’t light up.

sorry this is super long just looking for any answers or help on what’s happening thank you.

There’s no obvious solution to these things but they all have in common electrical issues. Loose battery connections, loose electrical components, bad ground connections, and or electrical stuff getting wet.

check your connections on your battery. Are they tightened down, need cleaning?
if horn does something weird when hitting bump, check the electrical connection to horn in front of radiator.
check for water leaking into headlight housing, check tightness of headlight plug connections.


that kind of stuff

^^ It is most likely a connection under-hood that has been affected in some way... but it might also be a problem with your headlight/high-beam/running-lights/fog-lights control stalk or horn wire.

However... my first thought is to ask you if you have lowered your car at all beyond 1-2". If your car is aggressively lowered it can happen that you hit enough bumps so as to have your driver's side front tire wear down the inner plastic fender liner. If that has happened then your tire may have begun to rub away the wire shielding on a very large bundle of body harness wires right in that location.

With aggressively lowered SC's it is highly recommended to do a body harness extension and slightly relocation in that area (basically you want that part of the body harness mounted higher inside that fender or routed above it in the engine bay-- by extending each wire in the harness).

If this is not your issue then please disregard the above notes and check all your underhood relays and fuses the steering wheel horn connection and inspect and test the lighting control stalk again both while driving and while parked.

...

A similar event happened to me once but only briefly:

My SC is not lowered but one time I had a good 450-500lbs of extra cargo loaded throughout the car during a long trip. This did make the suspension work harder and I do think the ride height was a bit lower than normal. My car is only lowered 1" from stock at most if even that much so I have not ever needed to do a fender well body harness relocation.

At one point I hit a sharp bump on a highway and all the lights on my dash and my high beams went out but the car was still running. Since I have a manual transmission model I shifted into neutral, shut off the engine and then restarted while rolling and coasting along. At that point the entire electrical system recovered completely and I was able to rev back into the appropriate RPM range, shift back into the appropriate gear and resume driving. You cannot do this with an automatic model so you would need to find a way to pull over to do the same.

After the fact I suspected that my extra cargo added so much weight that when my suspension compressed over that sharp highway bump it threw something off in my electrical system by just bumping the fenderwell body harness that I mentioned. My problem was never ongoing however but it demonstrates that in an extreme scenario this can happen.

It is far more likely to happen if your SC has been lowered with no fenderwell body harness extension and relocation.

this is not refuting Kahn’s ideas above…

I had a 92 Acura Integra that started having electrical issues while driving. Radio, ac, fan, dash lights would all cut off intermittently.

Checked battery charge and alternator, both fine. Realized it was happening when hitting bumps in road. Eventually found that one of the battery terminal connections was loose enough to alter the connections. Tightened it down and forever fixed.

sometimes it’s the simple things

Please let us know if you figure this out, it’s nice to get closure

This!!!! ^^^

Yowza, thank you GAsc300!! I can't believe I didn't think to mention that as well-- yes!

OP, as he mentions above, definitely check your battery negative and battery positive terminals for secure connection. Sometimes these do wear out and it can cure weird electrical issues to replace them with new OEM terminals.

For reference:

SC300/400 1992-2000 OEM battery terminal NEGATIVE -- P/N 90982-06022
SC300/400 1992-2000 OEM battery terminal POSITIVE -- P/N 90982-05030

Hey guys, finally getting back here, first wanted to thank you guys for replying, I do appreciate it, and second, I did some looking and it’s definitely the harness under the driver front fender. I’m not the first owner on my SC, or even the second, so I’m not sure exactly how much it’s been lowered but it is down there, and it has taken a toll on that wiring harness. Which leaves me to to either extend/relocate/repair all the wiring; or take it to somewhere/someone who could repair it for me, though I’m more than willing to repair it myself. Would you guys have any tips/advice for the job? Or know anyone in AZ I might be able to take it to?

I've done it myself on my car and to be honest it's not the worst job (that's coming from a guy with NO patience for electrical work and wiring)... Get yourself a nice heat gun and some solder/shrink connectors in various sizes (don't just use the crimp ons - pay the extra money for the ones that heat shrink with solder inside for a good repair). Take your time, pick through the harness after un-wrapping it, and start matching up wires. They're all color coded and quite simple to match up as you repair. Triple check EVERYTHING (I checked mine twice and still missed a couple of little spots where wires had been rubbed through) and also check the connector inside of the footwell to ensure it's plugged in completely (mine actually pulled out of the connector slightly). When you're done, wrap everything up nicely and you can simply tuck it above the pinch weld in the wheel well with some good zip-ties so that it's safely out of the way. I even ended up raising up my car slightly on top of tucking the harness up higher to hopefully avoid anything like this happening in the future lol.

Hey guys, coming back a little disheartened, just finished repairing and relocating the wiring harness and to my dismay almost nothing has changed. I didn’t do much in terms of lengthening or repairing for that matter, only a handful of the wires had been fully rubbed/worn through, and I added new patches of wire, soldered and heat shrunk them together, re ran the harness and plugged everything in. Triple checked as Rudy said and still nothing.

Here’s how the lights are acting atm

Off- no lights or anything
— - running lights
On - runnings lights
Auto - Driver side head light, both brights at super low level, running light on passenger side
Pulled towards driver - only driver side bright
Pushed away from driver - only drivers

It also acts differently when I unplug my passenger headlight and brights but I’m not sure how to explain, please ask any questions you have.

Fog lights are working fine, any other tips or advice? This is starting to drive me insane