W124/E220 immobiliser (?) problem

[david000762]

I have owned my 1994 E220 (W124 model) for many years. It is NOT equipped with the later "flip key" operated locking/immobiliser system. The car came with just two identical keys which fit the doors, boot, ignition and console box - no key fobs or anything else.

I had no trouble starting the car up to the day it was laid up about two years ago.

A few days ago, I decided to get it going again. The battery had long since expired so a new one was fitted. As soon as I connected the terminals, all of the indicators started to flash but this stopped after about 15 seconds. But as soon as I opened the drivers door, they started to flash once more; again stopping 15 seconds later.

When I turned the ignition on, the indicators started flashing again. I then tried to start the engine; it turned over but would not fire - this is because the fuel pump is not running.

If I disconnect the battery and then reconnect it with the ignition turned on, the fuel pump operates for a few seconds - so clearly all is well with the pump and its relay. Running a wire directly from the battery to the fuel pump causes it to operate and the engine starts - so the ignition circuitry is OK.

I have a dreadful feeling that the problem is caused by some sort of aftermarket alarm/immobiliser which has been lying dormant up until now. This suspicion is reinforced by the presence of an unused bracket under the bonnet which looks about the right size to hold an alarm sounder. I am led to believe that "add on" alarm/immobilisers were fitted by Mercedes dealers when the cars were new but, as I said, I have never had any indication that my car had one.

My first question is whether my theory is correct - if not, what else could be causing these symptoms?

Secondly, in the absence of any remote controller for the alarm/immobiliser, how do I go about disabling it to stop the flashing indicators and restore correct fuel pump operation?

Thirdly, why has this happened after so many years of dormancy?

And finally, where is this wretched alarm/immobiliser device likely to be located? Internet research has suggested that it might have been under the upper metal plate in the passenger (near side) footwell............but it isn't, although there is a multiway wiring connector attached to the lower plate.

Any help that can be given would be most gratefully received as I am getting more frustrated with the car by the minute!

Best wishes,

David.

 

[Bolide]

It's clearly got an alarm as the indicators flash. The simplest way to deal with it would be to hotwire it, take it to an alarm installer and ask him to rip out the system. He'll be able to find it so long as he's a time-served techie and not a teenager who's never seen a W124 before

Nick Froome
www.w124.co.uk

 

[david000762]

Thanks for your response Nick. I would prefer to tackle the problem myself if I can - not the least because the car is undriveable and at the moment is on a SORN and without insurance and MOT. I will continue investigating for a bit longer and if I can't fix it, I will see if I can find a mobile alarm specialist.

Best wishes,

David.

 

[Dec]

Secondly, in the absence of any remote controller for the alarm/immobiliser, how do I go about disabling it to stop the flashing indicators and restore correct fuel pump operation?

Most alarms will have some means to switch them off in the event of a fault so as the car can be driven, the means to do this is usually by a key switch, located within easy access, perhaps in the glove box OR under the steering wheel above drivers knees OR located on the alarm siren… this is not good in your situation as the alarm siren seems to be missing.

If there is no key in your possession for turning off the alarm, then the switch, if one exist and you can find it, could be modified by rearranging its wiring and so turning off the alarm.

Is there a wiring loom/plug in the vicinity of where you think the alarm siren is located?

Dec

 

[david000762]

Hello Dec and thank you for your response. I have searched high and low for a disable switch but can't find one. There is no glove box on this car as it is fitted with an airbag. There is nothing attached to the cowling under the steering column and all wiring to the alarm sounder appears to have been removed; it's only the bracket that is remaining.

I have just removed the cowling around the steering column and there is no sign of the control box under there either........

Best wishes,

David.

 

[Dec]

Well I think, as yourself that there is an alarm in there somewhere? and that’s what the flashing indicator lights are saying.
On my car for example there is a Red LED just to the right of the passenger air bag, this is to indicate that the alarm is armed when it is on, so do you have one, maybe on the inside of door or elsewhere on the car? You could use that to trace your way back to the alarm control box.

Dec

 

[david000762]

No there are no LEDs at all. I have been in touch with a MB "specialist this morning; he took my VIN no. and came back saying that he thought this was a non-UK model and that the immobiliser may be incorporated with the ECU........

Grrrr!!!

Best wishes,

David.

 

[david000762]

Success!!! I finally found the alarm/immobiliser box right next to the door locking air compressor under the rear seat squab. It is a Sigma Type SG2 and I have removed it and reconnected the supply to the injection fuel pump relay. The car started straightaway, with no flashing indicators, and I am back on track to get it MoT'd tomorrow.

Nick and Dec, many thanks to you both for your assistance - it is greatly appreciated.

Best wishes,

David.

 

[Bolide]

I think you're better off without an old alarm system. I'd fit a simple immobiliser (you can cook one up yourself) and a tracker if you're concerned about security

Nick Froome
www.w124.co.uk

 

[david000762]

Nick - all I wanted to do was to get the car to work so that i can MoT it and sell it. It - together with a newer W124 E280 wagon - has sat around for too long and it is time for them both to go.

So I won't be too worried about security!

Best wishes,

David.