1990 Factory Fit Alarm

[r129 300sl]

Hi all,

I was wondering, does the 1990 R129 Factory fit alarm have an immobiliser. I have fitted a Clifford immobiliser for insurance purposes but would like to know if there was already one fitted.

Secondly the driver side window will not go down with the window switch. It goes down when I put the top down. However if the window is in the down position and I press the switch to go down, the window goes up!!
In addition the passenger electric window occasionally does not go down when the top is raised or lowered.I have to do it with the switch.

Are these problems related or do I just need to replace the drivers side electric window switch?

Thanks

[bobterry99]

I don't think the car has a factory immobiliser, but Learoy has a schematic for a '92 which implies that it does -- at least for that year. But you can see for yourself. Lock the car, reach-in and open the door to trigger the factory alarm, and then try to start the car.

Your driver-side window switch is faulty. Here is how the switch works. There are two wires from the switch to the controller. When you press the switch to raise, one of the wires is grounded. When you press the switch to lower, the other wire is grounded. And when you press the switch past the detent to use the one-touch down feature, both wires are grounded. Your problem is that in this last instance your switch is only grounding one of the wires, and the controller gets a signal to raise. A replacement should be inexpensive, but if you like you can disassemble the old one and clean the internal contacts to restore its functionality.

If the passenger window does not go down automatically, I think it could be the switch in the bottom of the door is stuck closed and is signalling the controller that the window is already down. You can test this possibility by seeing if the one-touch down feature works when the window won't lower. I don't know for a fact, but I suspect it relies on the same switch in the bottom of the door to let the controller know when the window is lowered.

[LeaUK]

According to one of my schematics the starter immobiliser module (K38) was fitted to models up to '93 (and maybe beyond, but I cannot tell). But looking at other drawings (also referencing the K38) it appears that no K38 was fitted until '94. Some other drawings show the K38 being triggered by the ATA (pre '93) then post '93 triggered from the CL M14/1 module!

My car was manufactured in Dec '92 and definitely has starter cut out - so who knows!! Conflicting diagrams are the bane of my life when trying to resolve certain issues!

Anyhow, Bob's advice is the best. 'Break-in' and try and start the vehicle! But remember, the stock 500SL immobiliser isn't approved anyhow, so if you have or haven't got it, for insurance purposes you need that Clifford


Lea

[r129 300sl]

Hi

Thanks for replies. Bobterry I think you are right about the passenger side window. The one touch down function does not work. Where is the sensor that you talk about? Is it in the door? If so is it easy to get at and change?

As regards the driver window it prob. is the switch. How can I get it out? Do I have to remove the wood fascia?

Regards

[LeaUK]

The window down sensor is within the door panel at the bottom and it's relatively easy to get at, however, you will need to remove the door panel. Search on this forum (I think Bob made a post before) and you should find pretty detailed instructions on how to do this.


Lea

[bobterry99]

Wood must be removed to replace switches. Very easy to do if you have the radio removed.