1990 SL300 Factory Alarm System
 

Well here is another problem on my 1990 300SL.
The LED lights (Arm RED and Dis-Arm GREEN) in my door handles and trunk no longer function. The Alarm will not work as it did before. I have changed the batteries on both of my hand factory keyless units. I tried to re program the keys (when batteries go bad) This has happened over this past winter, it all worked flawlessly before. I looked for blown fuses, none that I could find. I know there is some sort of controls under the passenger side floor mat. If I leave all doors unlocked, I can drive the car. If I should lock the car, upon reentry and start the car, If I move the car a few feet the lights and horn flash, the engine still runs. The only way to stop the alarm is to take the key out of the ignition and put in drivers door (Outside) and turn key clockwise to stop it. Does anyone know what this problem is? Module etc.? Can I just unplug this from the under the passengers floor mat.? then what? I would like this to work as before as a fully restored alarm / warning system.

Thanks Guys AGAIN!!

Just trying to get a handle on your problem...

...you followed the procedure for reprogramming the keys after replacing the batteries (i.e. placing the key in the ignition and turning to position II for a few seconds so the computer can reinitialize the key chip)?

Also check the orientation of the batteries in the key housing. I have had mine stop functioning for no apparent reason until I readjusted the battery contacts, and verified that the batteries were installed properly.

I have two key units that were handed to me when we purchased our car (used), but only one of them works anyway. Replacements are $100+. :(

G-Benz...Thanks for the respose. The 1990 verison on your SL didnt have a chip in the key. In Reprograming the 1990 year you do it from the Drivers door. I checked the batteries with a volt meter on both hand held Alarm keyless remotes, they were good. I still replaced the one I use everyday. So I think that possibly the Alarm master "What Ever Module" is the problem. At this point I want to find out is that whats under the passenger side floor mat., and have some input as to disconnecting everything from here, or pull out the module and borrow another from an SL to see if this is the problem. If this was an everyday car I would fix it ASAP, but its my toy, and keep it under wraps in the Garage, till the driving season hits the North East.
Thanks Again..:cool: