Front and rear washers typically use the same pump usually located under the washer bottle.For front washers the pump runs forwards. For rear washers the rear washer switch supplies power with the electrical polarity reversed and the same pump runs backwards ,pumping to the rear of the car through a one way valve. As far as I can see there is just one fuse protecting both of these electrical circuits. ( I think it is a 15amp fuse ,number 21, but check this on the drivers handbook.)
So first check would be to see if this fuse has blown . If it has blown try replacing it. You might be lucky and it now works. But the problem might have been the pump was under excess load because of some sort of blockage such as dirt, scum etc in the washer bottle , so also try and flush the bottle out with a garden hose etc.
If the fuse blows again immediately or soon after there may be a fault or short circuit in either of the two switches, or their wiring, or the pump itself. This would need more detailed investigation to establish the source of the problem, and possibly replacement parts. If you are unable to do this yourself the cost would depend on how much labour or which parts are required. Its a job where owning a multimeter would be a great help in diagnostics. If you are willing to undertake diy repairs its worth buying one. (from about £8)
