* Ignition Switch: This is the most likely culprit. The ignition switch provides power to various circuits, including the fuel pump and headlights. If the switch is faulty, it might not be supplying power to the headlights but could still allow power to other circuits (like the marker lights) which may have separate power feeds.
* Ignition Switch Wiring Harness: Even if the ignition switch itself is fine, the wiring harness connected to it can be corroded, damaged, or have loose connections. This could interrupt power to certain circuits selectively.
* Fuse/Relay Issues (Less Likely): While less likely given the specific symptoms (headlights and fuel pump affected, but not marker lights), check the fuses and relays related to the headlights and fuel pump. There might be a blown fuse, but the different behavior of the headlights and marker lights suggests a more wiring or switch problem.
* Body Control Module (BCM) (Possible but less probable): In some vehicles, the BCM manages various electrical functions. While a faulty BCM could cause such issues, it's less likely than the ignition switch or harness problem given the selective nature of the failure.
Troubleshooting Steps:
1. Check all fuses and relays: Start with the fuses and relays associated with the headlights and fuel pump. Look for blown fuses (visually inspect for broken filaments). If a fuse is blown, replace it with one of the same rating. However, if it blows again immediately, there's a short circuit somewhere in the circuit.
2. Test for power at the fuel pump: With the ignition key turned on, use a test light or multimeter to check for power at the fuel pump's power wire. If there's no power, this confirms the issue is upstream of the pump.
3. Inspect the ignition switch wiring: Carefully examine the wiring harness connected to the ignition switch for any signs of damage, corrosion, or loose connections. Pay close attention to the wires supplying power to the headlights and fuel pump.
4. Test the ignition switch: This often requires testing power at various terminals on the switch itself with the key in different positions (this is more advanced and may require a wiring diagram).
5. Check the headlight switch: While less likely, a faulty headlight switch could be preventing the headlights from functioning.
Important Considerations:
* Safety: Working on automotive electrical systems involves the risk of electrical shock. Disconnect the negative battery cable before starting any work.
* Wiring Diagram: A wiring diagram for your specific 1995 Chevy Astro is highly recommended. It will show you which fuses, relays, and wires are involved in the headlight and fuel pump circuits. You can often find these online.
If you're not comfortable working with automotive electrical systems, it's best to take your Astro to a qualified mechanic for diagnosis and repair. A faulty ignition switch is a relatively common problem, but pinpointing the exact fault requires systematic testing.
