Alarm question 560SEL
 

Are the factory keys required to arm the alarm?

I have ordered a set of keys through the dealer, in the mean time I have been trying to see if the alarm works. So far I have not been able to arm the alarm. The only key I have is an aftermarket, laser cut key.

If this key should arm the system, then I can start trouble shooting, if not I'll wait for the real keys to arrive.

Mike,

To my knowledge, once the car is locked the alarm is armed. I could be wrong as I purchased a Viper alarm system right away, with key FOB etc. They now work in concert and it's always armed when I lock it up, same as it was before the Viper.

There is no special key, just the ignition/door/trunk key. When the alarm goes off, the head lights should blink and the car horn sounds.

Thanks Ted. I'll put "check all connections, etc" on the list. Mechanics first, the nice stuff last :).

Sure thing :)

It could be the Becker unit itself, behind the faux pass side firewall *or* it could be the wiring. I've heard of and experienced probs with the wiring in the door. Sometimes the window mechanism can mess things up, esp if someone has gotten the inside panel off in the past in order to repair a regulator or what have you. I suspect if you have a short the alarm would simply not shut off (in my case) or it's been disconnected altogether, probably your case. Good luck with the big Benz!

You may be right in the case of later 126 cars, but I can tell you from experience that my wifes 83 280SEL came with a wad of keys. Only the ones with the red dot on them would set the alarm.

I also can tell you that on early cars with standard keys the only difference between a valet key and the master was the blank it was cut on. One could cut a master from a valet by using the right blank.

OK, no alarm trouble shooting until the keys arrive from the factory. The manual definitely refers to the red dot, the factory keys are supposed to be red dot and the only key I have has no dot.

Dang, that almost sounds like morse code ;).

Interesting... I just checked my manual and there's no mention of a red dot key. Just a flat (for the wallet), valet and master key. It can only be armed by the flat or master by locking the either front doors or the trunk. It will sound if the doors, trunk, or hood are opened - or if the radio is removed or brake is depressed.

I guess the red-dot just refers to the master key and they changed the "lingo"...

Nonetheless, it sounds like you solved the problem.

The manual I'm refering to Ted is the service manual. I hadn't looked in the owner's manual yet, but I might later tonight just to see what it has to say.

Hi Mike
I only got one key with my 560 and it has the red dot and the alarm works
Maurice

MB got rid of the dot before 91. My 91 didn't come with a dot key.

Sixto
91 300SE
81 300SD

Here's my story.

Bought my 85 500SEL and it came with two keys, both MB, one with red dot (flat key is M.I.A)

Both keys lock the vehicle completely, but only the red dot sets the alarm. At the same time the sensor chip in the driver's door was (supposedly) worn out from years of use.

Using the red-dot key:
If I lock the drivers door, I could unlock anywhere and the alarm did not go off.
If I lock the passenger side, or trunk, and then unlock the drivers side, the alarm did go off.
If I lock the pass/trunk, and unlock the pass/trunk the alarm was set, but did not go off.

Using the plain key:
No matter what, the alarm never went off.

But ..
Using the red-dot on the pass/trunk locks to set the alarm, and if my wife came later with the other plain key the alarm always went off regardless of which door she used.

This all seems to confirm that
1) The red-dot key is the only one to set/disable the alarm
2) The sensor chip in my drivers side door lock is worn.

Part 2
 

My story Part 2 :

I have since purchased 2 new keys from MB dealer.
They do not have the red dot.

But ....
No matter what I do, the alarm does not go off.

(For example)
I can trunk lock the vehicle using the old red-dot key, and unlock the drivers side with a new key -- no alarm.

Are the new keys just like the old red-dot key?
Is the alarm being set with the new keys?
Do I still need to replace the drivers side sensor chip?

Sorry about the long story MT, but it may be worth something when you get your keys and start tinkering with the alarm.

What is this sensor chip? AFAIK, there's a pair of switches built into the door lock mechanism. Either the key triggers it or it doesn't. My driver side door only has one working switch -- on the lock side. I unlock the car, open the door and turn the key again to the lock position so the alarm doesn't go off. Bugs the heck out of my wife because she never remembers to give it a second twist. :)

Sixto
91 300SE
81 300SD

The alarm on my 1987 went off a couple of times with the red dot key. I guess the sensors are a bit worn. I am seriously thinking about disabling the alarm by unplugging it as it is embarrising when it goes off.

Old Blue - did you check with the Mercedes dealer to see if the ones they sent you should activate the alarm??? Just wondering if you have to specify.