I've had a 88 300E for about 2 months now. I read the owners manual and assumed the car didn't have an alarm as I don't have a key with a red dot and it never went off.

A least until Saturday morning when I opened the door (it wasn't locked.) The horn started beeping and the lights were flashing. I eventually disconnected the horn but the lights stayed flashing. They eventually stopped. (I didn't try the key in the door, would this have turned it off, I did try it in the ignition.)

It was raining fairly heavily out so I believe I have a short of some kind in the system. I would like some advice on finding the short if possible. Just places to look or common problems.

Also, If I do happen to fix the problem, how can I tell if I have a master key that will turn off the alarm (try turning it off, got that.) But can I get a master key if I don't have one.

Thanks for the great site. Looking forward to buying stuff here.

I too have an '88 300E. (None of my keys has a red dot either.) If you use the key to lock the doors (from either passenger or driver side front doors), the alarm will be armed. Also, If you lock the trunk (which also locks the doors) this arms the alarm. I have a problem now in which I lock the doors but the rear passenger side door does not lock, so I open the door and off goes the alarm.

To turn off the alarm place the key in either the driver or passenger side front door and turn the key. This will shut off the alarm.

The alarm will go off if someone tries to:
-Open a door
-Open the trunk
-Open the hood
-Remove the radio (stock radio that is)
-Switch on or bridge the ignition circuit
-Step on the brake pedal

The alarm will sound for approx. 150 seconds (the horn will honk for 60 of those seconds) with the lights flashing on and off.

On some models (190's I think) there is a way to dis-engage the alarm system all together. I'm not sure how/if this is possible on the 300E's.

Good luck!

Stephen Davis
1988 300E 90k miles "The Cabernet Cruiser"
MBCA - N. Texas Section

p.s. - did I answer question you already knew the answers to?!? Sorry if I did.

Me again.

I had an idea - Is the radio in your 300E stock or after-market? If aftermarket - how was the anti-theft wiring treated?

Also, if the ignition circuit could cause an alarm and this is one of the more likely palces to get wet - maybe you could check the connections at this point outwards. You may have a trick wire there.

Finally - check the sensors/switches under the hood & in the trunk. Maybe they are gummed up or not functioning properly.

Maybe one of the tech guys will have more light to shed on this.

Stephen Davis
1988 300E 90k miles "The Cabernet Cruiser"
MBCA - N. Texas Section

On all of the older MB's the control unit can be disconneted of its power and it will be disabled without having any problems with any other systems. The alarm can be armed and disarmed from the trunk as well.
On an aftermarket radio you just have to lay the harness for the alarm out of the way and it will ignore this part of the system.

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