Please Help

[nonsuch]

Have got 2005 focus tdi & recently it won't start it says steering assist failure . Some times it starts & drives fine .I have put key in ignition & gone from mark 1 to 2 several times & this sometimes works & it starts some days it works all day but just lately it won't start at all .been to a few garages but they don't no what it is .would be most grateful if anyone can help many thanks

[InKontrol]

Have you checked condition of the earth leads and tested the battery?

Also when you say it won't start does the engine crank over or do you simply get a clicking sound from the starter motor?

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[nonsuch]

When it don't start it don't turn over at all its as if the immobileliser is on . Sometimes when its going I lose all power & all the lights come on & I get steering assits failure but I pull over give it a min & its all ok again when this happens the heated front window does not work either .thank for your help

[Captain Peanut]

Is the battery getting/holding charge?

I had something very similar on my previous car (MG) and the alternator was giving up the ghost and not fully charging the battery.

[nonsuch]

battery is new . When car working fine it will start even if left a week