ASE A6 Electrical Test: Content Areas & Voltage Drop
The ASE A6 test certifies that you can diagnose electrical and electronic systems end to end — batteries, starting and charging, lighting, body electronics, and the networks that tie them together. It counts toward Master Automobile (A1–A8), and the hard questions are circuit-diagnosis problems, not parts identification: reading a voltage-drop result or a wiring diagram back to a specific fault. Get comfortable measuring drop under load and A6 stops being the test people fear.
This page covers what the test contains and how to study it. If you want to test yourself instead, take the A6 Electrical practice test — eight verified questions with explained answers.
What A6 actually tests
| Content area | ~Q | What it covers |
|---|---|---|
| General Electrical/Electronic Diagnosis | ~13 | Ohm's law, circuit testing, voltage drop, wiring diagrams and the diagnostic logic the test loves. |
| Battery & Starting System | ~9 | Battery testing, state of charge, starter draw and no-crank diagnosis. |
| Charging System | ~8 | Alternator output, regulation, ripple and charging-circuit voltage drop. |
| Lighting Systems | ~7 | Headlamps, signals, brake/back-up lights and lighting-circuit faults. |
| Instrument Cluster, Body & Accessory Electrical | ~8 | Gauges, wipers, power accessories, horn and body-control inputs/outputs. |
| Networks & Module Communication | ~5 | CAN/serial-data basics, module communication faults and U-codes. |
Question counts are approximate and show relative weight; the form you sit also includes unscored research questions. Confirm the current task list at ase.com.
It spreads across the whole low-voltage side of the car, but notice where the weight sits: general electrical diagnosis plus battery/starting and charging. That’s circuit work, not parts lookup.
Trace the starting & charging circuit
Starting & charging circuit
Where the voltage goes — and where resistance hides.
Battery
- Job
- Stores energy; supplies cranking current and stabilizes system voltage.
- How it fails
- Low state of charge, low capacity, or surface charge fooling a quick test.
- Symptom
- Slow crank, low resting voltage, fails a load test.
State of charge and capacity are different measurements — an open-circuit voltage reading is not a load test.
Voltage drop is the whole game
If you take one thing into A6, make it voltage drop. A circuit can show full battery voltage at rest and still fail under load because resistance in a connection or ground steals voltage the moment current flows. The test repeatedly hands you a “voltage is present but the device won’t work” scenario and checks whether you’d measure drop across the connection under load instead of declaring the circuit good.
This single habit covers dim lights, slow cranks, low charging, and intermittent accessories. Techs who chase continuity with the circuit dead get the easy half right and lose the diagnosis half.
It’s the difference between two tests techs constantly confuse:
Voltage-drop test (under load)
- Circuit is live and working
- Measures voltage lost across a connection while current flows
- Finds resistance that only shows up under load
- What ASE wants
Continuity / 'is there power?' check
- Often done with the circuit dead or unloaded
- Passes a connection that fails under load
- Misses the most common A6 fault
- The tempting wrong move
The call: When a device won't work but voltage is 'present,' measure voltage drop across the connection under load — feed AND ground.
Where techs lose points
| Symptom | Real cause | Exam trap / correct call |
|---|---|---|
| No-crank, good battery | High resistance in starter feed/ground | Drop-test the circuit; don't condemn the starter |
| Battery keeps going low | High-resistance charging connection | Not automatically a bad alternator |
| Dim lights, ~full voltage at connector | Ground-circuit resistance | Small feed + ground drops add up under load |
| Many unrelated electrical faults | A shared bad ground | Check grounds first, not each component |
| Key-off battery drain | Parasitic draw | Measure controlled key-off current; don't guess |
A worked question
A customer's headlights are noticeably dim. With the lights on, a voltmeter reads 12.6 V at the battery and 12.4 V at the headlight connector. What's the most likely cause?
- A Weak battery
- B Burned-out bulbs
- C Excessive resistance in the ground circuit✓ correct
- D Failed alternator
The battery is fine (12.6 V) and the feed is nearly full, so the loss is on the ground side. With the lights on, drop-test between the lamp housing and battery negative — a meaningful drop means the current is fighting a corroded or loose ground. “Voltage present” checks never catch it; drop under load does.
Exam trap: The 12.4 V feed reading looks 'almost full,' which is the trap. Small drops on BOTH the feed and ground sides add up to dim output. Measure voltage drop on the ground side under load and you'll find the corroded or loose ground.
A study plan that fits the test
Build the foundation first — Ohm’s law and voltage drop, then series/parallel circuits, then reading a diagram — and only then drill the specific systems. A6 punishes guessing harder than most A-tests.
You’ve planned 32 hours (8 × 4). This compares your planned time to a typical prep load — it’s a planning gauge, not a prediction of your exam result.
- Wk 1General Electrical/Electronic Diagnosis
- Wk 2General Electrical/Electronic Diagnosis
- Wk 3Battery & Starting System
- Wk 4Battery & Starting System
- Wk 5Charging System
- Wk 6Lighting Systems
- Wk 7Instrument Cluster, Body & Accessory Electrical
- Wk 8Full-length practice + review every missed question
Quick check
A headlight circuit shows nearly full voltage at the connector but the lights are dim. The best next test is:
A6 hands you wiring diagrams constantly, so make sure you can read every automotive electrical symbol cold before test day. When you want to be tested rather than taught, run the free A6 Electrical practice test or pick another series from the ASE practice test hub. For the broader system context, see electrical & HVAC study, and line up A8 Engine Performance next since it builds on these same fundamentals — A7 Heating & A/C leans on the same circuit-diagnosis skills on the controls side. Review the ASE test fees before you register, and note that each cert expires after five years — plan your recert window early.
Frequently asked questions
Why do so many techs fail the A6 test?
Because they study parts instead of circuits. A6 asks you to read a measurement — usually a voltage drop or a diagram — back to a fault. Techs who check 'is there power?' and stop there miss a whole category of questions that hinge on resistance under load.
Do I need to pass A6 before A8?
It's not required, but it's smart. A8 Engine Performance leans on the same circuit-diagnosis fundamentals. Passing A6 first makes a large block of A8 far easier.