Alarm troubles on an '89 300 E
 

I've just recently purchased an 1989 300 E from a private party and when I open the door from the drivers side the alarm goes off. I've been reading the forums trying to figure out the alarm on this car and believe I'm having a similar problem to the person in this thread:
http://www.peachparts.com/shopforum/showthread.php?p=1081291

I'm not having any problems with the lock in regards to the person in that forum, the car locks and unlocks just fine, but when I do open the drivers side door it doesn't seem to register with the alarm system and it goes off. Sometimes I fiddle with the door lock and it stops buzzing, or if I start the vehicle the buzzing stops. I still need to figure out how the alarm works on this vehicle, then figure out whats wrong with it. Any advice or information for a factory alarm off a 124 sedan would be nice, or if you have a solution to my problem I would appreciate it.

Thanks in advance,
Jamie

I do have information the alarm system and how to test system. It sounds like you have bad sensors.

Yeah, any information you have would be appreciated. Anything that would help me diagnose and fix this problem. I don't know anything about how the alarm system works on this vehicle.

UPDATE:
After checking this vehicle out a bit further, I realized a few things:

• the drivers side door will only lock with the key, when I press down the inside door locks, they all go down, except the drivers door remains unlocked. I don't know if this is a actuator problem in the drivers door perhaps?
• When I unlock the car with the key, the alarm goes off when I try to start the car.
• The only time the alarm does not go off, is when the car thinks it's locked. I.E. if I lock the door again via the key before getting in and starting it, or if I leave the drivers door "unlocked" since when I lock the doors the drivers side doesn't actually lock due to the suspected actuator problem.

So now I have 2 problems instead of just one. If anyone has any thoughts to either the alarm or the door lock problem feel free to help.

Sounds like the driver's door switch is the culprit. There is a switch that goes to that door handle that is used to arm/disarm the alarm when the key is turned or when the car is unlocked with the master key.

First, check the vacuum lines to that door lock actuator. Make sure it's getting vacuum signal. Check by the vacuum pump and see if you have any cracked Y connectors there. Those like to rot out.

If you're getting good vacuum signal to the door, then put a hand vacuum pump on the actuator element. Pump it down and see if the door locks. Using the dial, see if the element HOLDS the vacuum. If it doesn't then it's got a cracked diaphragm and needs to be replaced.

That's a good place to start.


-tp

need your email so I can send you some pdfs