Ever turned the key to find nothing happening ?!?!

You press the alarm button again and again and finally the engine springs to life. 

Must be the alarm/immobiliser obviously. ..Well, maybe not.
This is actually a classic sign of your ignition electric switch getting worn and your car will eventually not start at all.

These seem to go between 120K to 160K miles depending on use and this is not a 5 minutes job so if you start getting the symptoms, do not wait as you won’t be able to fix this by the side of the road….
 
There is a small electric unit on the back of the ignition barrel held in by two screws which controls all the switching to the starter motor and other electronic parts of the car.
 

This can be removed and replaced but is a tricky job due to the lack of room behind the ignition barrel.
To create a bit more room I loosen off the ignition barrel.
This is done by rotating the plastic cap around the ignition key.
When removed you will see two rivets and two breakoff bolts:
 

 
These will need to be drilled off to remove the metal plate.
Another technique is to cut a groove in the top on the rivet with a Dremel and use a flat head screw driver the remove them.
When removed the ignition barrel will be loose and will give you a bit of extra space but there still may not be enough space.
At the bottom of the barrel there is a screw which locates in a circular recess on the ignition unit as shown below:

I removed this screw which loosened the ignition unit to create more room.
 
There are two screws holding the electric unit in place.
You may be able to get a small screw driver on the heads to undo them. First the electric connector needs to be removed and pushed out of the way.
You can see the two screws on the back of the ignition barrel:

When you remove the electric unit and replace it with the new one it’s important to make sure the location key is aligned with the hole in the electric switch:



The location tab in the centre of the circular part has broken off.
The tab locates with the cross in the middle of the electric switch:

 
Tightening the screws up when they are not aligned can be a very expensive mistake.
This will break the tab in the barrel and you will need a new expensive ignition barrel.
Some people remove the facia to aid removal of the metal plate as shown below.
 

 
Once the ignition switch is screwed in place the connector needs to be put back on and the barrel re-installed.
You can use normal nuts to locate the barrel or the proper break-off bolts and rivets.
 
Taking off the front driver’s seat may help you with having more access to carry out this work. 
 
Richard Stephens
911SC Technical Advisor