* Battery/Alternator: A weak or failing battery or alternator can cause low voltage, leading to erratic operation or complete failure of electrical components. This is a prime suspect given it affects multiple systems. Check the battery voltage (should be around 12.6V when not running, and 13.5-14.5V when running). Have the alternator tested at an auto parts store.
* Fuses/Circuit Breakers: While unlikely to affect *all three* systems simultaneously if they have separate fuses, a blown main fuse or a faulty circuit breaker could cause widespread electrical issues. Check the fuse box under the hood and inside the car (usually under the dashboard). Look for blown fuses (a broken filament inside) or tripped circuit breakers (often a small reset button).
* Ignition Switch: A failing ignition switch can interrupt power to various circuits, including those controlling the systems you mentioned.
* Wiring Harness: Damaged, corroded, or loose wiring in the main harness could disrupt the power flow to multiple systems. This is more likely to affect systems near each other, but a significant break in the main harness could affect everything. Look for visual signs of damage, especially near connectors.
* Body Control Module (BCM): The BCM is a central computer that controls many electrical functions in the car. A faulty BCM could cause widespread electrical problems. Diagnosing a BCM issue requires specialized tools.
* Grounding Issues: Poor electrical grounding can prevent proper voltage flow to various components, leading to malfunctions. Check for corroded or loose ground connections, especially near the battery.
Troubleshooting Steps:
1. Check the battery voltage: This is the easiest and quickest check.
2. Inspect fuses and circuit breakers: Replace any blown fuses and reset any tripped breakers. Note the fuse ratings to replace them with the correct ones.
3. Visual inspection of wiring: Look for obvious signs of damage, corrosion, or loose connections, especially around the battery and fuse boxes.
4. Have the alternator tested: This is crucial as a failing alternator can cause low voltage and erratic electrical behavior.
If none of the above reveals the problem, you'll likely need a qualified mechanic to diagnose the issue further. A scan tool capable of reading codes from the vehicle's computer systems might be helpful in pinpointing the problem. Focusing on the battery, alternator, fuses, and wiring harness is the best starting point for a DIY approach.
