How To Fit an Alarm Tilt Sensor
 

First off, thanks to Phil-T4 for the instructions on doing this, as requested, here is a How To for fitting a BMW tilt sensor to your 75 or ZT.

First of all, you will need a tilt sensor as fitted to a BMW E38, E39, E46 or similar, part number 65.75.8.386.932.9. Ideally you should buy one with a plug and a bit of loom for connecting to. If yours doesn't have a bit of loom and you have a spare door loom, find the multiplug for the electric window switch and cut that off as it is a perfect fit (thanks BigRuss).

https://i.imgur.com/hE2KANt.jpg

The BMW wiring at the sensor plug is as follows,

Pin 1 - Black/blue - BCU output
Pin 2 - Black/red - Earth / ground / 0v
Pin 3 - Red/black - 12v alarm switched
Pin 4 - Black/red - Earth / ground / 0v
Pin 5 - Black/red - Earth / ground / 0v
Pin 6 - unused

Pins 4 and 5 are connected inside the sensor itself to pin 2 so there is no need to connect these. I removed them from the plug to avoid confusion.

The pin numbers are clearly marked on the plug, and on the inside of the socket if you haven't got a plug.

https://i.imgur.com/tR0Pb9z.jpg

https://i.imgur.com/ppViSrx.jpg

You need to open the glovebox all the way by pinching the hinge together to allow full opening of the glovebox door.

Remove the four TX20 screws at the top of the glove box,

https://i.imgur.com/N0Oa69Z.jpg

Then peel up the mat from the base of the glove box to reveal these three TX20 screws and remove them,

https://i.imgur.com/DT8tumQ.jpg

You can now partially remove the glove box, being careful of the plug for the glovebox light on the left hand side as it easily catches on the dash and becomes damaged. Unplug the light and CD changer if you have one fitted,

https://i.imgur.com/TpRAwRr.jpg

Now looking inside the hole, you can see the BCU. It is secured left and right with 8mm bolts, loosen these bolts a few turns and slide the BCU towards the engine to release it.

https://i.imgur.com/pXTAK2l.jpg

Once it is off its mounting you can unplug it, this is the plug that you need to connect to,

https://i.imgur.com/6Z1se49.jpg

Looking at either side of the plug, you need to release the blue retaining tags and slide the black housing away,

https://i.imgur.com/nC3dktS.jpg

Once you have slid the black part of this connector away, you will be left with two blue parts from inside which hold all of the pins. Slide the two parts apart and locate pin 32 which is in the middle row. The pin numbers are marked on the blue plastic, it should be unpopulated,

https://i.imgur.com/4FkeZa2.jpg

You will need a spare pin to put into this connector, it simply slots and clicks straight in. This needs to be connected to pin 1 of the sensor plug,

https://i.imgur.com/iaHy6ne.jpg

Next you need to find pin 15, it is on the other side of the plug and should be populated with a pink/yellow wire, this is the switched alarm live and should be connected to pin 3 of the sensor,

https://i.imgur.com/Zl9U522.jpg

https://i.imgur.com/UL9DMtN.jpg

Reassemble the plug by sliding the black part back on until both blue parts click into place.

I chose to use one of the bolt points for the negative connection, remove this press stud in the footwell trim,

https://i.imgur.com/XBculsG.jpg

Pull back the rubber door seal to show the brass coloured clip,

https://i.imgur.com/EBEZdw7.jpg

Then tug the bottom of the trim towards the centre console to release it, you will see this earth point, connect pin 2 of the sensor to this,

https://i.imgur.com/aySPQKZ.jpg

As my car is an automatic, I chose to mount the sensor here, this is the same orientation as the fitting in a BMW, if you chose to mount it elsewhere, it should be mounted flat,

https://i.imgur.com/eX27VQn.jpg

At this point, I tested the sensor, shut yourself in the car, making sure all the doors and windows are closed, lock the car using the keyfob. Wait about 40 seconds for the alarm to be correctly active, then tilt the sensor, the alarm will sound.

Just to recap the connections required,

Sensor pin 1 - BCU pin 32
Sensor pin 2 - Earth / 0v
Sensor pin 3 - BCU pin 15

If you are planning on going on a ferry and do not wish the sensor to be active, lock the car using the key in the drivers door lock, just as you would with the ultrasonic sensor.

I currently have spare pins to fit the BCU plug, if you send me a PM, I will give you the details to pay for one, They are £1 each to cover postage, envelope and my inclination.

Disclaimer:
You are responsible for any work or modifications carried out on your car and you undertake any such work at your own risk. Neither The 75 and ZT Owners Club nor the original author of these How-To's can be held liable for anything that may happen as a result of you following these How-To's.
Any modifications should be reported to your insurance company.

Thanks! Just what I needed. I'll PM you about those pins (I don't have any).

Good job Rich :D

Nice one Rich :bowdown:.

Now included in the How To's

Good work Rich.

Are the BCU pins the same as almost all of the female pins used on the car? They look the same in your pics but it's hard to tell. Just be useful to know before pulling the the BCU out.

Not sure to be honest.

They are different to the ones in the sensor plug, which Russ says is the same as the window switch plug.

I have plentyof the right ones if you need one.

Nice Job Rich, thanks. I now know what my next mod will be :bowdown:

Thanks for the how to, Rich.
Do you know which of the wires is input or output?
I have a plan to to fit a GSM relay to control the FBH + heater fan and some of the units have an input which I believe could be connected to the alarm system. The idea is that an SMS would be sent to my phone when the alarm is triggered.
The input on the GSM box takes 5-14 VDC and the question is, which wires should be connected to it?

If pin 15 is the common output from the BCU to the several sensors and each of them have a separate input to the BCU, perhaps it should be connected in parallel to the horn output?

How sensitive are these Rich? Wouldn't want it going off if someone *passed wind* (damn swear filter :p: ) near it (or maybe I would ;) ) but I'd also like it to go off if the car was rocked or knocked

I am no small lad, with me vigorously shaking the car it wouldn't go off.

But, try jacking it up to remove a wheel or get underneath, and it goes off well before the wheel leaves the ground.

I assume it has some intelligence built in so that wind or passing vehicles do not set it off.