I didnt no

Bought the car and was advised the amp was damaged. He replaced with a different amp and wasnt even for this car. Bought VCC p/n 31215615. This is the same amp which was damaged.
In replacing the stereo works for 1 minute then turns off and the sat/nav or stereo stops working.
When you stop lock the car and then unlock it does the same.

Was advised it was just a case of a straight switch. Any ideas on what im doing wrong