The rear wiper on my 07 plate V70 has stopped working.

I have checked the fuse and that is OK.

So I'm thinking I have a broken wire in the loom and most likely the earth as neither the intermittent or continuous settings work.

There are three wires going to the motor, white, yellow and black.

I presume that the black is the earth but can someone confirm this before I start cutting the wires to run a seperate earth.

Thanks.