R1100RT Ignition Sensor

Testing and replacing the 2av54 vane sensors

 13/06/03

The only two R1100's I know of that have broken down did so because of ignition sensor failure. A sensor plate can cost up to £170 in the UK, in Switzerland an awful lot more! So here we will look at testing and replacing failed sensors to save a little money.

The Honeywell 2av54 Hall Effect Switch

How does it work

These sensors are the electronic equivalent of ignition points. There are no moving parts except for the vane that passes through the sensors gap.  The bright wedge shaped piece is a magnet, across a gap, it's facing a hall effect transducer (magnetic switch). When the gap between them is obstructed, the lines of magnetic flux are broken and transducers output is switched off, this causes the electronics to fire the spark plugs.

Front and rear views of the ignition sensor plate from the R1100RT. The two sensors are triggered 180deg apart, first one sensor is triggered then the other, half a turn later.

Part number for the BMW R1100RT is 12 11 2 306 137

It's made by Bosch and stamped with Bosch part No. 0232101022

Note: other machines in the R1100 series use different ignition sensors, or at least they have different part numbers!

Sensor plate electrical layout

The schematic below should make it clear where each wire goes and what it does, note the top wire (clear) is the screen wire, the cable is like Arial coax, screened to prevent interference.

Sensor plate plug coupler

Testing

Building and using a simple test set

To find out which sensor(s) have failed you need a simple test set. All you need to build it are the following parts, a 12v power source, three small insulated crocodile clips, wire, heat shrink tube and a 12v LED,  that's an LED that's had a resistor built in to make it work from a 12v supply.

To test the LED put the white and black crocs together, the LED should light. Follow the schematic diagram below:

Important: Do not use a conventional bulb of any kind, it will draw too much current and damage the sensors irreparably.

Below is the test set schematic. It's shown set up to test the upper sensor, if you want to test the lower sensor the white wire goes to terminal 2 instead of 5.

The test set shown testing the upper sensor, as in the diagram above.

Any good sensor should light the LED until something metallic, like a feeler gauge, is introduced in to the sensors gap, the LED will then go out.

Any sensor that doesn't light the LED or doesn't go out when the sensor gap is obstructed is defective.

Using the test rig on this sensor plate showed the lower sensor was defective with no output (the LED didn't light).

Replacing a sensor

1. Undo the cable clamp for the defective sensor, these screws are tight, use a big screwdriver that fits properly and press down hard when you turn.

 2. Centre pop the sensor rivet heads accurately and drill the rivet head off with a 3.5mm drill. Don't drill down too far because if you drill slightly off centre you will drill the sensor plate, then when you come to fit a new sensor it might not locate correctly.

 3. Carefully cut through the heat shrink and wires at the red marks below to release the sensor from the plate.

I recommend you cut in to replace the sensors at the red marks or near by, do not cut in to the "grey area" to make your connections as there are a lot of fine connections under the heat shrink, you really don't want to go there.

Mounting the 2av54

The 2av54 sensor rivets have a locating pin, so I made up a small mandrel to support the bottom of the rivet. Mine was made by hand from 5mm Stainless Steel rod with a 3.5mm hole drilled in the centre to a depth of approx 3mm.

You might well be able to rivet without a mandrel, that's up to you.

Macro picture of the mandrel tip.

Sensor and plate mounted on the mandrel ready to be rivet down.

Mount the mandrel very tightly in the vice, locate the sensor and plate on to the mandrel then rivet down with a flat punch.

Before you start riveting, double check it's all located correctly!

Once the new sensor is fitted it only remains to wire it in.

You will need a small pair of side cutters, small soldering iron, insulating tape and heat shrink tube to fit.

Wiring is obviously colour to colour.

Tin the wires after cutting to length and striping the ends. Next slide on the heat shrink tube. You could use two short pieces to cover the joint over lapping them when you shrink them down.

Next solder the wires together, I wrapped each joint with a small piece of tape after soldering, but you could use small bore heat shrink tube.

When all three joints are made, pull the heat shrink over the joints, refit the cable clamp and shrink them down. While it was hot I moulded the heat shrink to shape and pressed it down on to the plate.

Sensor plate completed & tested.

Ignition timing

After replacing the sensor plate you will need to check the ignition timing, you can do this with the test rig above or with a voltmeter.

To test with a volt meter, plug the sensor plate in to the bike and switch on the ignition. Put the negative clip to a good earth on the frame and the positive probe to the Orange wire in the coupler (upper sensor). Watch the meter as you slowly turn the engine clockwise (viewed from the front)

Timing is correct when the voltage drops to zero with the OT (TDC) timing mark central in the window

Honeywell reference literature

2av54 Data sheet

2av54 Engineers line drawings.pdf (right click, save target as)

2av54 Dimensions

2av54 Block circuit diagram

Other reference pages

http://www.roadkill.com/~davet/moto/timeCanister.html

http://home.jps.net/~snowbum/Ignition.htm

http://www.geocities.com/fwarner_au/mc_things/bmwr_ign_sensor.html

Availability

The Honeywell 2av54 is available from UK electronics supplier Farnell at around £10 each or Newark in the USA
(Farnell obtain the parts from Newark taking around a week to arrive form the USA).

Disclaimer

Any modifications you carry out on your machine are done so entirely at your own risk

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