Blower motor diagnosis
Blower speed surges randomly, then sits at a steady low speed when the control panel is unplugged.
What this lesson covers
CORE TEACHING Blower motor; resistor vs electronic controller; high-current feed; ground; PWM/analogue control; fail-safe/default strategies. PRACTICAL DEMONSTRATIONS AND TESTS Check motor power/ground; controller input/output; unplug control panel; measure control signal; scan HVAC commands. ADVANCED / SCAN TOOL LAYER Scope command waveform and motor output/current. Compare requested blower percentage with waveform duty. KEY DIAGNOSTIC QUESTIONS Is the motor healthy? Is controller receiving a sensible command? Does fault follow command or high-current stage? MUST-COVER CHECKPOINTS Map simple vs module-controlled architecture; prove heavy power and ground; verify switch/request; command output; measure load current; inspect signal/network where used.
What you will be able to do
Blower speed surges randomly, then sits at a steady low speed when the control panel is unplugged.
Where it sits in the programme
- Builds on
- Lesson 30: Exterior lighting and strange voltages
- Feeds into
- Lesson 32: Fuel pump electrical diagnosis