Breaker tripping in circuit with a contact
We have a circuit controlling 3 outdoor flood lights on our house in standard Red Dot fixtures. These are controlled by an Intermatic T101 timer. The timer also controls the outdoor lights for our garage which are on a separate circuit. When the timer signals on, the garage lights work, but the breaker for the house light trips. I presume when the Intermatic timer signals on, a contact is set, and the house light circuit activates. This timer itself will not support two separate circuits. Our breaker panel shows a breaker for the timer and a separate breaker for the house outdoor lights.
What systematic testing would you do to find the problem?