On the left hand side of the battery are 3 connections, 1 earth and 2 plugs.
Circled below shows the earth and the motor power connector.
On a disassembled PAS (power assisted steering) rack you can see the connections more clearly.
Circled in yellow are the 2 possible earth connections. These corrode which can affect the connection. Pull the connection off and clean with sand paper or wire wool.
A spray of contact cleaner on the tabs and connections will also help.
Reconnect the earth connection. You will only have 1 earth cable and you
may have 1 or both of the connection tabs. Whichever one you use is fine.
The final 2 main connectors should be sealed but it is always worth the time to disconnect
them and give all parts a quick spray in contact cleaner before reconnecting all
of the connectors. The top connector in the picture is the power to the power
steering motor, the lower of the 2 connectors is the column rotation sensor.
This should sort out the intermittent nature of the steering fault.
Check the cables coming away from the steering rack, you are looking for splits
in the sheathing ,chaffing and obviously cables that have been cut through totally.
Check for water under the carpet. The PAS controller is attached to the centre console,
underneath the dash, in the footwell, hidden by the carpet. Although it is unlikely,
there is a small chance that this controller could become water damaged.
While you are looking at it, ensure the connections to it are OK and pushed in tightly.
Pull fuse 35 for the power steering and replace it with a fresh one, make sure it's tight when
reinserted as a loose fuse could cause intermittence through the vibration of the engine.
There is a possibility of debris getting into the steering rack. Check the rubber bellows
on each end for splits and make sure the clips are holding rubber bellows in place.
If your rack has become contaminated there isn't much you can do apart from replace
it or try to take your existing one apart to clean it out, if you do attempt that, good luck.
Also called switch cleaner. It can be bought from places such a Maplin.
If you are an online buyer then Google or Ebay search for contact or switch cleaner.
Servisol and Ambersil both do such a product and neither are expensive.