Safety and setup
Meter inspection, CAT awareness, stop conditions, and the port map.
FREE DOWNLOAD / FIELD CARD 01CONVENTIONAL 12 V
Automotive electrical diagnosis
Put the meter
on the right points.
An 11-page bench reference for safer meter setup, loaded-circuit testing, voltage drop, key-off draw, sensor checks, and faster next-test decisions.
Get the free PDF No card / immediate download
0111 pagesFast bench reference
028 workflowsFrom source to proof
03Loaded testsEvidence over guesses
04$0No card required
Inside the field card
One test.
Then the next right test.
The quick reference is organized around probe placement and operating conditions. It tells you what the reading means and what it does not prove.
Modes and probes
What each mode tells you, whether the circuit is powered, and where the probes go.
Source checks
Battery and charging clues without pretending one number fits every vehicle.
Voltage drop
Positive-side and ground-side tests that reveal resistance under load.
Controls
Fast checks for fuses, relays, switches, and current-carrying ability.
Sensor circuits
5 V reference, signal, low reference, NTC, Hall, VR, and PWM basics.
Key-off draw
A controlled in-series workflow, sleep-state cautions, and false-result traps.
Decision path
No-power and intermittent-fault flowcharts plus an evidence record.
Actual pages
Made to be used,
not admired.
Keep it on a tablet, print a shop copy, or pull up the exact test beside the vehicle. Large diagrams and short notes keep the meter setup visible.
Download the complete reference
!Know where this
Stop conditions
Know where this
guide ends.
- Orange high-voltage hybrid or EV cabling
- Yellow SRS or airbag connectors
- Pyrotechnic battery disconnects
- Damaged high-current wiring
- Unknown modifications or unfamiliar systems
Use trained help and the correct vehicle service procedure. This guide is general education for conventional 12 V circuits, not vehicle-specific service data.
When the quick reference is not enough
Go from a reading
to a defensible diagnosis.
The full 30-page Automotive Electrical Diagnostic Guide adds circuit theory, worked cases, CAN basics, printable worksheets, and expanded flowcharts.
Before you download
Clear answers.
No open circuits.
01Is it really free?
Yes. No payment card is requested. The email form creates your private download link immediately.
02What vehicles does it cover?
It teaches general methods for conventional low-voltage 12 V automotive circuits. Vehicle-specific service information always controls the actual procedure and limits.
03Can I use it on a hybrid or EV?
Not on orange high-voltage cabling or components. The guide also excludes SRS/airbag connectors and pyrotechnic devices. Those systems require qualified procedures and equipment.
04May I print it?
Yes. The personal-use license allows you to save, print, and annotate your copy. Sharing, resale, uploading, and redistribution are not permitted.
05What emails will I receive?
The guide is delivered immediately in the browser. WrenchCircuit may later send occasional product and project updates. You can unsubscribe or request deletion by emailing Wrenchcircuit@gmail.com.