Complete starter motor diagnosis
Turn the key: click, slow crank or nothing. Prove battery, cables, control circuit and starter before replacing anything.
What this lesson covers
CORE TEACHING Starter construction; solenoid; B+; trigger terminal; motor ground through case; pinion engagement; click/no crank; no click; slow crank. PRACTICAL DEMONSTRATIONS AND TESTS Battery check; B+ at starter; trigger voltage during crank; positive and ground voltage drop; current draw; temporary control test only where safe. ADVANCED / SCAN TOOL LAYER Scope cranking voltage/current; scan start-request PID, immobiliser/start-authorisation status where supported. KEY DIAGNOSTIC QUESTIONS Does it receive the request? Does the solenoid act? Does the main motor get power? Can hundreds of amps return through ground? MUST-COVER CHECKPOINTS Separate control circuit from high-current circuit; prove battery first; B+ feed; trigger; positive drop; ground drop; current; mechanical result.
What you will be able to do
Turn the key: click, slow crank or nothing. Prove battery, cables, control circuit and starter before replacing anything.
Where it sits in the programme
- Builds on
- Lesson 6: Current and amperage
- Feeds into
- Lesson 8: Starter relay and start-control circuits