Here's a breakdown of the possible causes:
* Wiring Issues: The most common culprit. A wire might be loose, shorted, or incorrectly connected to the lighting circuit instead of the accessory circuit. This is especially true if modifications have been made to the vehicle's electrical system.
* Faulty Relay: Relays are switches that control the power flow. A malfunctioning relay related to the accessory power or lighting could be causing the unintended power flow to the stereo.
* Damaged Ignition Switch: Although less likely, a failing ignition switch could be sending power to the accessory circuits even when the key is not in the "accessory" or "on" position.
* Aftermarket Stereo Installation: If the stereo is aftermarket, the installation may have incorrectly wired the power connections.
To fix the problem, you'll likely need to:
1. Inspect the Wiring: Carefully examine the wiring harness connected to the stereo. Look for any loose, damaged, or incorrectly connected wires, particularly the ones supplying power to the radio.
2. Check Fuses and Relays: Check the fuses related to the accessory power and lighting circuits. Also, locate and inspect the relays associated with these circuits. A bad relay could be causing the crossover.
3. Trace the Power Source: Use a multimeter to trace the power source of the stereo. This will confirm whether it's getting power from the correct circuit (accessory) or incorrectly from the lighting circuit.
4. Consult a Wiring Diagram: A wiring diagram specific to your 1997 Dodge Ram 1500 will be invaluable in tracing the power circuits and identifying potential problem areas. You can often find these diagrams online or in a repair manual.
If you're not comfortable working with car electrical systems, it's best to take your truck to a qualified auto electrician or mechanic. Incorrect wiring can lead to further damage to your vehicle's electrical system.
