How-to: Disable alarm on a 1993+ W124
 

This is my write-up for those people who have a funky alarm like mine. I have been putting this off for a while now, but decided to tackle it since i had the cluster out for some other work....

The problem: alarm goes-on when i unlock the car from the driver's door.

Solution: Disable the alarm. You can try to fix it, but i understand it will cost a fortune, and too much of a headache for me. Besides, i don't need it !!!

Step 1: Disconnect the car battery so that the alarm does not go-off, or you get hit by an airbag while removing the cluster.

Step 2: Locate the alarm. In my case, it is under the passenger's feet. remove the floor mat and the foam-backed carpet piece. Unbolt the bolt holding the black plate in place. The alarm is the black box on the left with two big plugs going into it (second picture).

http://i893.photobucket.com/albums/a...Q/IMG_3964.jpg

http://i893.photobucket.com/albums/a...Q/IMG_3965.jpg

Step 3: Unplug those big plugs. On pre 1993 cars, this should be sufficient to disable the car. Not the case though for 1993+ cars as they have an immobilizer feature that is triggered when the alarm is disabled. so my car would not start after unplugging those two plugs.

http://i893.photobucket.com/albums/a...Q/IMG_3966.jpg

Step 4: You have to find the relay with the name k38. It is located under the instrument cluster. by jumpering this relay, you will be able to by-pass the immobilizer, and have a fully functional car without the alarm. So proceed to removing the instrument cluster as seen below, that is the nastiest part of the job as that thing is tricky....in the picture, the cluster is removed

http://i893.photobucket.com/albums/a...Q/IMG_3967.jpg

Step 5: Locate the k38 relay. it is in the upper left corner of the cluster space. it is shiny silver in color on my car....pull it out by hand- easy!!

http://i893.photobucket.com/albums/a...Q/IMG_3968.jpg

http://i893.photobucket.com/albums/a...Q/IMG_3969.jpg

Step 6: in order to bypass the immobilizer feature, you need to jumper pins 30 and 87 on the relay, see the picture below. I ran a copper wire between the two pins. Make sure the wire is as flat as possible so that the relay seats properly

http://i893.photobucket.com/albums/a...Q/IMG_3970.jpg

http://i893.photobucket.com/albums/a...Q/IMG_3972.jpg

Step 7: put the relay back in place. connect the battery without tightening the terminal. try to start the car, if it starts, remove battery terminal and install cluster.

Step 8: tighten battery terminal, and enjoy your car with no annoying alarm !!!!!:thumbsup::thumbsup::thumbsup::thumbsup::thumbsup: Easy job over all. the hardest part was removing the cluster.....

Good Luck, Thanks for the help with this guys!!!

Very nice description and pictures. the alarm was giving me a problem on my 400e, so I disconencted it and the car wouldn't start. I tapped the alarm module (you know like you used to tap the tv when the picture shrank, or got squiggly) and it's worked fine since then. (Probably just reseating the connector took care of the problem.)

I would imagine that jumpering the purple wire to the purble/green wire would accomplish the same thing. Now you can remove the relay and little the car up a little. :D

Or put a kill switch in by cutting the red wire and wiring to +12 via a toggle switch, or secondary key.

Which got me to thinking, why not find the wire coming out of the alarm that triggers the K38 relay? Tie it to ACC and be done. No need for cluster removal. :eek:

I had the cluster out since my odometer was not working, fixed both at the same time...

I liked to do it this way in case the next owner decides to fix the alarm correctly...if i it gives me trouble, i will make it more permanent...The reason for this write-up is to document in pictures the wonderful advice given to me here, and to help some other people also who might be unsure about how to do this :)

This thread is where i got the info from, this is such a great forum..
http://www.peachparts.com/shopforum/tech-help/203412-95-e320-alarm-goes-off-no-reason-3.html?highlight=k38+relay

Special thanks to Kestas and others for their help on this :)

Note that for the 94-95 cabriolet, the alarm unit (ATA) is accessed from the trunk and located in the left rear fender well, behind the trim.

Awesome latief, you da man. What was the problem with the odometer?

Also - I do believe that one cause of the alarm problem you are having is the vacuum door lock actuator. I have the same alarm problem you do but mine is intermittent. My door lock vacuum actuator is dodgy anyway so I am replacing that first and then we'll see if that fixes the alarm.

Once you get your trans fixed, with all this other stuff you've done, your car should be in pretty fine fettle :cool:

Last time I jumped a relay like that I had a fire :D

So you think i will be in trouble? I could not think of any other way to do it....

My door actuator seems to be working fine, ever since i got the car the alarm will go off if i unlock the driver's door. not any more...

Hopefully, it will not catch fire as Panzer said, :eek:

The Odometer stopped working for a day after i reset the trip repeatedly while driving. i did not get the memo about not doing that:o

thanks,

Well, in my instance, I was powering lights, so there was alot of current, I imagine with an alarm system there wouldn't be much current. and I see it's the 30x pins jumped, that shouldn't be trouble some, just eliminates the NO/NC functioning.

Thanks, that is a relief:)

What's wrong with resetting the trip meter while moving? I didn't get that memo either.

How did you fix the odometer? Mine is inop too. Do they break in a common place? BTW, that's great info on the alarm. Thanks.

If the alarm won't disarm at any given door the problem is most likely the alarm switch installed in the door (pn A0028201010 for the left door of the W124 E320). However, the switch does list for $177 (ouch). Mark

If you push the trip reset while moving, you risk something coming loose in there especially as the car ages....apparently, the cog responsible for both odometer and trip meter pushes itself out of place :(

See here....

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1495093-odometer-not-working-question-picture.html

Actually, both the odometer and trip meter are inop, so maybe the gear in the picture is responsible. Thanks.

Very easy fix...go for it!!!! :)

Thanks again. I'll probably wait until I find an LED display for the inop outside air temp and do it all at once.

HELP !!!
 

Hello, i read this topic as i have read hundreds of related topics and i am stuck...my battery from my 95 convertible drains when i leave the car for more than 24 hours...the battery is good, the alternator too...i have measured the drain and the car draws a steady 0.4A at all times...while searching for the problem i noticed that the horn for the alarm was disabled by the former owner...when i hooked it back up, the horn sounds...this makes me think that the alarm is faulty and in someway is always active,thus draining the battery...i tried to find the module, but cannot find it...i looked under the passenger footwel..nothing...i looked in the back of the trunk (took all the carpets out)...nothing...i should have a module as i have the horn installed...could anyone give me any idea where to look further...i am tired of charging my car every other day....thanx

Not sure about this one buddy, could be under the rear seat? or trunk panels somewhere....

Post a separate thread in the forum, and you will get much more repsonses than on this thread..

good luck

I have the exact same problem with my 95 E320. I too have disconnected the horn, but my lights start flashing when the alarm goes buggy.

As mentioned earlier in this thread, I was told the unit is in the left inner wheel well, behind the trim in the trunk, and that removing this unit will solve the problem. I removed that unit, jumpered the relay in the dash, and thought all was good. Now two years later I learn that the car still flashes its lights, and the unit I removed from the fender well (part number A 124 820 19 89) is a radio amplifier.

Just like you, I'm back to square one.

Ignition kill relay
 

I did not know how to jump the ignition kill relay:confused:

Latief, thanks much for figuring this out, and posting pics to show us:):)

Worked perfectly
 

I am not sure how you figured out to bypass the security system this way but I just did it on my 1993 300D and it worked flawlessly. Thank you very much. It worked exactly as you showed in your photos. :)

I discovered on my 1995 E320 you only need to ground connection 1 on the 14 pin connector at the ATA. This has the same effect as bridging the relay behind the instrument cluster and is a lot easier. Here is a quick test procedure.

Take a piece of wire about 2 or 3 inches long and strip both ends. Pull the 14 pin connector off of your ATA. Try to start the car, it should not turn over. Take the wire and bridge pins 1 and 2 (pin 2 is a ground) by sticking the wire in. Try to start the car, it should start.

I have had the wire in for several weeks now with no adverse effect.

Here are the wire function on my 1995 W124 E320 Pin Outs for 8 and 14 pin Plugs at the ATA:

8 Pin Plug (X2)

Connector 1 = Horn (yellow/black with red dashes) When power applied activates alarm horn on driver side fender under the hood

Connector 2 = Right front side light (grey) When power applied it turns on right front side light only (weird)

Connector 3 = All side lights, front and rear (grey/white) When power applied it turns on all side lights, front and rear

Connector 4 = 12V positive from auxiliary fuse holder (red/white [thick]) Constant 12V+

Connector 5 = 12V positive from auxiliary fuse holder (red/yellow [thick]) Constant 12V+

Connector 6 = Arm signal (yellow/pale blue + yellow/dark blue)

Connector 7 = Disarm signal (yellow/green x 2)

Connector 8 = Headlamps (yellow) Lights the low beam headlamps only when voltage applied


14 Pin Plug (X1)

Connector 1 = Power (brown/purple) To starter kill relay (K38) behind instrument cluster, you can over-ride K38 kill relay by grounding this wire.

Connector 2 = Ground (brown x2) Ground wires

Connector 3 = Power (red/white) 12V+ constant

Connector 4 = Trunk activation (yellow) Pulse activation from trunk.

Connector 5 = Unsure (green x 2) Pulse activation from left front door?

Connector 6 = Unsure (blue x 2) Pulse activation from right front door?

Connector 7 = Front doors (brown/grey) Open connection when either front door is closed, short to ground when either front door is opened

Connector 8 = Rear doors (brown/white with black dashes) Open connection when either rear door is closed, short to ground when either front door is opened

Connector 9 = Hood (brown/red) Open connection when hood is closed, short to ground when hood is raised

Connector 10 = Trunk (black) Open connection when trunk is closed, short to ground when trunk lid is raised

Connector 11 = LED (green/white) + connection to dash mounted LED

Connector 12 = Radio removed input (brown/dark blue) 12V+ when radio is in, radio out 0V

Connector 13 = Applied brakes input (black/red with white dashes) 12V+ when ignition is on and brakes are applied, no apparent function with parking brake

Connector 14 = Ignition “On” input (black/red) 12V+ when ignition (not ACC) is on, 0V when ignition is off

I have verified all the connections. I installed an after-market alarm (Bulldog) using these pin-outs and it works perfectly.

Bump
 

for customer

slick jumpering at the ATA!

:-) neil

Pin 1 to pin 2 connecting -instead difficoult remowing cluster to K38 relay - is a great solution, congratulation, thank you. IO am just upset about factory online ETM, they forgot about X42 location. There would be much easier grunding (or install an emergency switch) please help me about X42 location, at 1995 W124 ( E320) where is it??

On my 93 mercedes 300se w140 the relay behind the cluster its on the right side, and that is a buzzer when u leave yours or key inside..

How is it performed on a 92?

I have a 93 mercedes 300se w140, doe any one knows how to disconnect alarm. Right now the car won't start, and have no idea what to do. HELP

A 1992 and earlier does not have the K38 starter lockout relay (the one behind the instrument cluster). To disable the alarm just unplug in under the passenger footwell and operate the vehicle as usual.

where is the K38 on a 1995 s500 coupe? how do I identify it?