Strange Headlight/High beam Issues

With the high beams off, the low-beams and the DTR lights are on. When I turn the high-beams on, the low-beams turn off and LEFT DTR turns off, the RIGHT switches to the high beam setting. The dashboard indicator stays off. I tried getting a new switch (inside the engine fuse box) but it seemed to just alternate what lights stayed on and which turned off. I should sit down and try to decode that puzzle but wanted to verify that there wasn’t another hidden switch (maybe in the box under the steering wheel?) I just replaced all four lights as I thought they were dead, now I’m not so sure.

There would be a relay and the wiring to th light. You can swap relays as a test if it has the same number. I’d suspect the wires itself or ground. I’d the wire and run a test wire to see.

What are DTR lights?

Daytime Running - low setting on the high-beams (that’s how I saw them being referred to online).

Thank bing, I’ll try to find the relay to test that. I am not sure I have the skills or materials to swap out the wires, but maybe I can at least pinpoint the issue to save a diagnostic fee at the mechanic. The wires could be bad as I did have a mouse in the car a while back and he may have done all sorts of damage unseen.

What year?

2004 Civic Coup.

A good mechanic or shop is going to do a diagnostic so that they fix the actual problem and stand behind their work . If they just repair what you tell them to do and it does not solve the problem you will have wasted money.

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This may be a bit tricky to find…

The DTL, or more correctly DRLs, are wired in series when on to make them less bright. When you turn the low beams on, they are wired in parallel so they are brighter. The low beams always shut off when high beams are selected.

That said, check for bad ground connections. Electricity can find strange paths when ground wires are broken or corroded.

Wait, the low beams shut off when the high beams turn on? I saw a video where they stayed on… Maybe I’ve been losing my mind over nothing.

In that case the left high beam works on daytime running setting, but not on high (bulb is brand new). I’m going to try the switch again to verify it’s behavior.

Then maybe rip apart the center console to clean out mouse debris and check for chewed wires (poison is in the car, all mice should be dead by now).

Most of the wiring and relays for this are underhood, not in the console.

Relay works so it’s definitely the wires. Glad to know I can pretend I didn’t see the nest in the console for now. I’ll focus on the under dashboard and hood areas.

Relays, relay plural. It takes, I think, 3 to handle this.

Left and right in the under the hood fuse box. I don’t see any others listed

Look for a DRL relay.

I may have had a mouse? Details details details. If you bring it to someone, don’t forget that detail. Now look for chewed up wires. Underneath stuff.

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Yes, that’s the case for all cars I know.

It was the fuse, half of them are bad. The lights work now!

Yes, I should have suspected a nest in the trunk equated to a nest in the console as well and mentioned that earlier. Didn’t see that nest until I was looking for more relays under the dash and started wondering about wires.

But good news is it was a fuse, or more correctly half of them (the swap I initially did still failed because the spare and I think the abs were also dead). Now a whole new set of fuses and I have lights. Thanks for your help!

I expect this is going to be nearly impossible to resolve without the aid of the car’s wiring schematic. I’m presuming the model year is 2000 or later. You might have a chance without the schematic if 1999 or earlier. If you’d prefer to solve this yourself, suggest to focus your efforts on obtaining a copy of the wiring diagram, rather than replacing stuff on random guesses. Depending on model year, the pertinent info can be found in an aftermarket repair manual (Haynes/Chiltons) or from a service data base, such as All Data or Mitchells. Short term subscriptions to those kinds of databases for one car are usually reasonably priced. Another idea is to get a pro mechanic to diagnose it for you, then you can do the actual repair yourself if you like, replacing only what’s needed.