vegas240

Hi Everyone!

I'm new to the forum and just purchased a his/her's pair of 300E's. I've got one '89 and one '90.

I'm having an issue with the '89s factory alarm system. When i try to lock the doors using the key, the alarm goes off. What can i do to fix this?

Thanks!

-Kevin in Las Vegas

Lucky13

Welcome vegas! The first thing to do is STFF. I'll give you the Reader's Digest version: W124 is notorious for bad alarm controllers. It's about $125 to replace with salvage or e-bay, fairly simple DIY. Search to find it. These guys know their stuff and almost everything has been covered somewhere. You will find everyone helpful but search first, then ask specifics. Good luck, you have a great set of vehicles!

whipplem104

The easy answer is unplug it. It will not effect anything else.
The not so easy answer is that some contact is bad and causing the alarm to go off or the unit is bad as stated above. There is not a easy diagnosis of this system other than testing every item individually.

vegas240

Thanks for the info guys, i've tried searching and nothing covers this specifically. Does anyone have a diagram of the wiring schematics or MB testing procedure for this? Also, if i disconnect the alarm, will the doors still lock/unlock the same?

Thanks again for your help!

BENZITCH

I would first replace the aluminum fuses in the fuse box with the copper ones of the same size.

The aluminum fuses can get voids in them from the contact with the copper fuse holders over time, leaving gaps.

I have cleaned up quite a few electrical gremlins this way.

They are always available on EBAY priced reasonably.