I just installed a new stereo and now my running lights are always on even when I turn headlight switch off. It is a U.S. car and everything else is working fine.

If it worked before the stereo, look for burned fuses. Check for a.c. signals at the coils and injectors. Is there fuel pressure at the schrader valve on the fuel rail? Try scanning the computer for hints.

replace switch

I don't have a wiring diagram ,but on most cars I would say your low beam bulb is bad. Try swapping sides to see if the problem goes with it, or just replace the bulb. You can always keep the new one until needed someday... shadetree mech by necessity.

This is just an idea, I may be wrong but any input is helpful, right? I would think that the switch that controls the plow lights is designed to alternate between the circuits for the truck light and the plow light. If the trucks headlight switch is turned on then the circuit is closed and turnes on the light. When the plow light switch is turned on it may cut the hot side of the circuit going to the headlight and engage the hot wire to the plow light. The headlight and plow light may share a common ground. If they don't share a common ground then the plow switch may cut the ground wire opening the circuit. If you can't find a solution you can always wire the plow lights directly to the battery with the same switch or a new toggle switch and then turn on the parking lights only on the truck. On most GM cars and trucks there is a space in the fuse pannel that is for a power accesory. It is basically a fuse slot that is empty labeled ACC. This is a 12V hot power source and you would run the positive wire here then ground the neg to the chassis. This way if you forget to shut off the toggle it will cut the hot when the key is shut off. When running the wire it is near the hood release able and you may be able to run the wire thru there and not drill a new hole. I've done this for neon lights under cars as well as stereo systems requiring an amplifier. If you drill a new hole even though its under the hood I would put a little blue RTV silicone over the new hole to prevent moisture from getting past the fire wall or road salt.

SOUND LIKE FAULTY DRL HEAD LIGHT RELAY.CHECK HEAD LIGHT RELAYS YOU HAVE RELAY STAYING CLOSE NOT OPEN TO TURN OFF CONTROL CIRCUIT TO HEAD LIGHTS.

Start by setting your auto headlight switch to off if this solves it replace your headlight switch If your car is equipped with daytime running lights there could be a short bridging them with your auto head lights look for broken or frayed wires do this also if you have installed or had someone install an aftermarket stereo or speakers/sub woofer, amplifier. Good Luck with this

Hi there. You need to tap into an ignition live wire. This means that it can not be used when the ignition is off. If you have a volt meter you can put the negative to the chassis and positive to fuseboard turn your ignition on and off you will get voltage to this when ignition is on . you will also get permenant live do not connect to these.

There are fuses for each headlight under the hood, against the passenger's side fender, in a relay box that includes the clutch relay and main relay. Make sure these are not blown and getting constant power (they are 'upstream' of the switch, so they should always be 'hot'). Then, check for power to the switch, and finally power to the lights.

Well...lets start with the obvious. Check fuses and NEVER piggyback any stereo or security stuff into their fuses...you dont want the lights to shut down during a night drive!!
Check under the hood for a relay center...also has some fuses there as well.

The Daytime Running Lamps are a "straight through wiring configuration". Doubt it even goes through a headlight switch at all.
But the regular lights do.
Unless you've worked on the front of the car and forgot to plug the headlights back in, do this...
Turn the light switch on...looking at the instrument cluster , can you make the high-beam-indicator light come on?
As you rotate the headlight switch knob...does the instrument panel lights brighten or dim? You probably have a faulty headlight switch...auto stores have them...they simply plug in.

Pull instrument/ cluster panel and re-melt cold solder joints where circuit board connects to dash connectors. Get them hot enough to turn them bright silver, usually 3-5 seconds each pin.
Good Luck!