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.