ASE A6 Electrical Electronics Practice Test

Door lock circuit.

43. The door locks in the circuit diagram above unlock only. There is no lock action when the switch is depressed. After replacing the door lock relay, there is still no door lock operation. Which of the following is MOST likely causing this condition?

  • A. A faulty switch.
  • B. The wrong type of relay.
  • C. A blown 30 amp fuse.
  • D. A faulty circuit breaker.
Door lock circuit.


Answer A is wrong. Neither switch will lock the doors. Notice the diodes in each of the relays.

Answer B is correct. Not all relays are the same. Some relays contain clamping diodes that protect sensitive control circuits.

Answer C is wrong. Clamping diodes are installed in reverse bias across the coil and allow current to flow in only one direction. Answer B is correct.

Answer D is wrong. Answer B is correct. A circuit breaker will affect both door lock relays.