![]() Why Are My Lights Dimming and Brightening in My Car? We discuss the main causes of car lights dimming and brightening randomly and we also share simple solutions to this problem. Sometimes you may notice your headlights are too dim or too bright, and there are several reasons why this may be happening. Also, every time you drive with dim headlights you are putting yourself and other people at risk. Whether it is just a dark day with poor visibility, or you are driving at night, your car’s headlights help you to see and will alert other road users to your presence.ĭriving with headlights that are too dim is a driving offense that may just land you with a hefty fine. Outside of checking the connections and wiring there is not much you can do without a scan tool.Car headlights are essential to keeping drivers safe on the road. You can see the FEM, G304, and C179 in the picture below. S139 Dash panel to headlamp junction, near T/O to C192 Front Electronic Module (FEM) G304 is connected via C179 (C means connector) and through S139 (S means splice)Ĭ179 is located behind the LH side of the instrument panel So where do you go from here? With or without a scan tool, the grounds are a good place to start. Outside of security theft deterrent systems they allow the aftermarket professional scan tools to access their systems. You many even need a factory scan tool, though I doubt if for a Ford. You will likely need a scan tool to diagnosis the car, and not a cheap one, but a professional model. This system was an early Multiplex design that reduced wire and total circuits where the modules communicate on a single serial line, now referred to as the CAN Bus (Controller Area Network). The FEM grounds the headlamps when it wants to turn them on. The Front Electronic Module (FEM) to be exact. If this sort of thing is actually happening, it is rare because I have not been able to confirm it.Ĭurrently, I have a "quick disconnect" on the battery and I always disconnect the battery when I park.īasically your headlamps are controlled by a computer. I can't be sure of this because it could have just been a matter of looking at one place or another while the lights were turning on/off, and thinking some lights were on and others were off. It seems that sometimes, the parking/tail lights will come on but the headlights will be off, or the left tail light will be on, but the right tail light will be off. Some other oddities that I'm not sure of. It seems it was rare at first, but it happens all the time now. This has happened since I purchased the car used. I Popped this panel out, and removed the connector from the back of the headlight switch, and the headlights remained on.Īs far as I know, when the headlight switch is turned on, the headlights remain on, at least that is what I have observed, but there may have been times where the flashing occurred with the headlights switched on, but I didn't notice. The headlight switch is mounted to a small plastic panel that snaps in/out from the dash. The issue occurs day or night, and regardless of whether the ignition key is on or off or removed, and regardless of whether the engine is running or not. The headlight system is a "standard" system, meaning there is no feature to "automatically" turn the headlights on/off based on the ambient light level. Sometimes the lights come on and stay on without flashing, and sometimes the lights stay off for a while, but then come on later. This will be on and off every 2 to 5 seconds (sometimes more), but it is not consistent. Sometimes, when this happens, they will "randomly" turn on and off a few times or more. If they are off, usually, within minutes, they will turn on, by themselves. Sometimes the headlights will turn off as expected, but sometimes they stay on. Typically, after parking, I'll turn off the headlights and remove the ignition key. The headlights (and parking/tail lights) intermittently come on (and off), even after the headlights are switched off.
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