Not a big issue but every time I start the car I get nag prompts stating that both auxiliary rear lights are on and I should check them. They aren't, the main bulbs are working fine. Strangely I get a slightly different message if I do remove the main bulbs but then it just simply states that the rear auxiliary lights are in use, no mention of checking. I've tried resetting the fault using decent garage software but it doesn't work. My battery or alternator or possibly both are a bit crap (I occasionally get that prompt too) and I suspect that will be the issue but I'm a bit skint at the minute and need to leave it a while. Could it be anything else?
The car uses current draw on the circuits to determine if a bulb is out. Sometimes incandescent bulbs will have a higher than normal resistance before they actually fail.
The solution is to either replace the bulbs, or add a resistor to draw slightly more current on a given circuit. No need to go crazy here - you just need to change the value enough to fool the car computer.
If the car thinks the bulb is still on, that is a separate issue. But sometimes these cars can do wacky things. Have you disconnected the battery before? If done improperly (reconnecting the negative cable before positive), the front SAM can be permanently damaged.
The solution is to either replace the bulbs, or add a resistor to draw slightly more current on a given circuit. No need to go crazy here - you just need to change the value enough to fool the car computer.
If the car thinks the bulb is still on, that is a separate issue. But sometimes these cars can do wacky things. Have you disconnected the battery before? If done improperly (reconnecting the negative cable before positive), the front SAM can be permanently damaged.
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The solution is to either replace the bulbs, or add a resistor to draw slightly more current on a given circuit. No need to go crazy here - you just need to change the value enough to fool the car computer.
If the car thinks the bulb is still on, that is a separate issue. But sometimes these cars can do wacky things. Have you disconnected the battery before? If done improperly (reconnecting the negative cable before positive), the front SAM can be permanently damaged.
I have disconnected the battery and it has also gone completely flat, I could well have just chucked the leads back on in any old fashion. BTW what is a SAM? ... ... Module? I've seen them mentioned loads, I assumed it was a fancy term for the fusebox. Is it something else?Originally Posted by slammer111
The car uses current draw on the circuits to determine if a bulb is out. Sometimes incandescent bulbs will have a higher than normal resistance before they actually fail.The solution is to either replace the bulbs, or add a resistor to draw slightly more current on a given circuit. No need to go crazy here - you just need to change the value enough to fool the car computer.
If the car thinks the bulb is still on, that is a separate issue. But sometimes these cars can do wacky things. Have you disconnected the battery before? If done improperly (reconnecting the negative cable before positive), the front SAM can be permanently damaged.
The SAM (signal acquisition module) is a PCB that is attached to the fuse box. The W203 has 1 in the front and 1 in the rear, both attached to their respective fuse boxes. In your situation, I would check both. The lights you're having problems with are in the rear of the car, but my understanding is the front one is usually the one that fries when the battery is improperly reconnected.
The other option is to figure out which relay drives the auxiliary lights and swap positions with another identical relay. Relays can go bad but it's extemely rare.
The other option is to figure out which relay drives the auxiliary lights and swap positions with another identical relay. Relays can go bad but it's extemely rare.
