Before you start searching for a break in the wire, best practise is to measure the resistance of your wire installation.
You should measure about 2,2 Ohm per 100 meter of wire.
If it is significant higher, you most probably have a poor connection or a break in the wire.
There are several ways to find a break in the wire, but the most comfortable and effective way is to use a cable detector.
TIP:
It can also be used to detect other cables like power lines in your household.