ASE Practice Test (A6: Electrical/Electronic Systems)

Question 1

A circuit has a specified voltage drop of no more than 0.5 volts across a switch. The measured drop is 1.8 volts with the circuit loaded. This indicates:

Accepted Answer

Excessive resistance in the switch contacts

Answer

Excessive voltage drop across a switch indicates high resistance at the contact points — often caused by corrosion, pitting, or loose connections. Voltage drop testing is the best method for finding resistance in a loaded circuit.

Question 2

A technician is testing a blower motor circuit. The motor runs slowly at all speeds. Using a voltmeter, full battery voltage is present at the motor connector with the switch in HIGH position. The MOST likely cause is:

Accepted Answer

High resistance in the ground circuit

Answer

If full battery voltage is present at the motor but it still runs slowly, the problem is in the ground return path. Excessive resistance in the ground circuit restricts current flow, reducing motor speed. A faulty resistor would cause a no-operation condition at that speed, not slow operation at all speeds.

Question 3

When using an oscilloscope to test a crankshaft position sensor, the waveform shows a missing tooth pattern. This is:

Accepted Answer

Normal — the missing tooth is a reference gap for TDC

Answer

Most crankshaft position sensor reluctor wheels have a missing tooth or gap machined into them as a reference point that the ECM uses to identify TDC (top dead center) for cylinder #1. This is by design and not a defect.

Question 4

A vehicle has an inoperative power window on the right rear door only. All other windows work normally. The MOST efficient first test would be:

Accepted Answer

Check for battery voltage and ground at the right rear window motor

Answer

When only one window is inoperative, the problem is isolated to that circuit. Checking for voltage and ground at the motor quickly determines if the issue is in the switch/wiring (no voltage) or the motor itself (voltage present but no movement).

Question 5

A diode in an alternator rectifier bridge is shorted. This will MOST likely cause:

Accepted Answer

AC ripple voltage to appear on the DC output

Answer

A shorted diode in the rectifier bridge allows AC current to pass through rather than being blocked. This causes AC ripple to appear on the DC charging output, which can be detected with a voltmeter on AC setting or an oscilloscope. A reading above 0.5V AC indicates a bad diode.