Power steering failure / Not Charging

[LesH]

Our Mercedes W169/A180 2.0 diesel had an intermittent power steering fault, whereby the red "Power Steering Failure" message would appear and the steering became very heavy.

This got worse over a few days until the warning message was on continuously and the steering was heavy.

The AA guy came out and said voltage at the battery terminals was fluctuating with load between 11.4v and 14.4v, so he said it is likely alternator issue (apparently the power steering is powered directly from the alternator?)

Replacement alternator ordered from an alternator specialist up north, fitted but the problems have got worse... not only does the power steering not work but we now have a battery not charging warning as well.

I accept that it could be a faulty alternator, but as they are tested before they leave the depot it seems unlikely...

Is there anything that needs to be done when changing the alternator that my mechanic may have missed? eg resetting the ECU or similar... or is there something else that could be the culprit...

Otherwise I will have to pay for a couple of hours additional labour to get the "new" alternator off and sent back for testing...!

Any advice or suggestions welcome!

Cheers.

 

[LesH]

Quick update.....
With the new alternator voltage at the battery terminals was 11.49v, and the display shows battery charge warning and power steering failure when the old alternator was put back on the voltage at the batter terminals without load was 14.4 volts, and the display just reads power steering failure.
So I suspect the new alternator is faulty??

So what should I check next?

Is there anyway to directly test the power steering pump?? Is it possible to just connect a spare battery to the pump terminals or is that too simple?