docstal

OK guy's I need some advice on a 2001 C-320. Immediately after locking the doors with the key fob the tail lights and front fog lamps begin blinking and continue to do so until I unlock the car and then reset by starting the car.
I've heard this may be a symptom of the backup battery going bad in the built in alarm siren???
If anyone else has experienced this problem and has a fix I would appreciate any advice.
Also, if it does need replacing where and exactly how is the siren removed/replaced and anyone know of an aftermarket replacement piece?

laneshift

Yes! This also happens to me! Except it's the instrument cluster that flashes after locking, and perhaps the turn signals for me.

I'll hang around to see what boils up.

nobli

did u recently change them?

docstal

No Nobli, I haven't replaced anything as of yet, I'm hoping someone had the same issues and the siren fixed the problem before tearing into it.
I am however going to try the recommended fix I found here for the seat modules that are both faulty and currently unplugged on my car. There is a thread for rewiring the seat plug wiring to allow the seats to remain plugged in and operable and not drain the battery.
For anyone with battery draining problems that keep popping up try unplugging the connectors found under the front of both front seats. I did this and the problem stopped immediately. What a wonderful piece of craftmanship we all drive!!!!!!!!!!!!!

nobli

ya, how dare we be so spoiled with the craftsmanship of our engineering masterpieces that the only thing we will ever have to complain about is a faulty battery and an uncommon and rare problem. come on now... you can drive your car to hell and back and that motor would still be reliable.

Now, on topic. i had a similar problem with my 194 wedge bulbs in the front. they would blink when hitting unlocked and give me an error message while driving. a simple resistor fixed that.

docstal

"spoiled"...."engineering masterpieces" ??? Your killing me! Obviously you don't drive a W203 model Mercedes. I've never owned a more finicky auto in my life. What other cars can you experience $900.00 seat modules that fail in the majority of these cars and drain the batteries. Or an electronic system that malfunctions during the common task of replacing an expired main battery...... and as far as the lights continuing to blink after locking the doors, I found through trial and error that it is a faulty alarm siren that has a built in backup battery that when it needs to be replaced will put the car in alarm immediately after locking the car. I fixed the problem by first locating the siren behind the passenger side wheel well and simply unplugging the connection for now. As far as the seat modules go, I fixed that problem with some searching here for information in other threads and simply wired the constant 12v wire on each module together with the 12v key controled wire. Now the seats work great (although you can't adjust the seats without the key on) and the battery stay's charged. Your right.....a definite "masterpiece" for sure!

jcnash

This is a standard security feature. If you leave your keys in the socket with the engine off and *shut* the door, the lights (instrument cluster + city lights) will flash 5 times as an indication to the owner that the keys are left inside. Happens on all W203's.