Possible Problems (in order of likely complexity):
1. Blown Fuse(s): This is the easiest and cheapest fix. Your Astro likely has an inline fuse for the tail lights and another for the dome light/brake lights (possibly a single fuse for both). Check your owner's manual for the fuse box location and diagram. Replace any blown fuses with the correct amperage.
2. Bad Bulbs: While you suspect more than just bad bulbs, it's crucial to check each bulb (tail lights, brake lights, and dome light) to rule them out. A simple visual inspection often suffices.
3. Faulty Wiring: This is where things get more complex. Worn, frayed, or corroded wires are common culprits in older vehicles. The wiring harness for the tail lights, brake lights, and dome light may have a short, a break, or a loose connection somewhere along its route. You'll need to trace the wiring harness carefully (a wiring diagram will be invaluable) to locate the problem. This can involve significant time and effort. Look for places where wires may rub against metal, especially near sharp edges or moving parts.
4. Brake Light Switch: The brake light switch, located near the brake pedal, is a common source of brake light problems. A faulty switch can prevent the brake lights from illuminating, and may also affect other circuits depending on how the wiring is designed. Replacing it is relatively straightforward, but requires some mechanical aptitude.
5. Multi-Function Switch (Turn Signal/Wiper Switch): In some vehicles, this switch also controls the brake lights. A problem here is more complex to diagnose and requires disassembly and replacement of the switch.
6. Grounding Issues: A poor ground connection can affect multiple lights. Check all ground points for the taillights, brake lights, and dome light circuits for corrosion or loose connections. Cleaning them with a wire brush and re-securing them is crucial.
7. Central Control Module/Body Control Module (BCM): While less likely, a failing central control module or body control module (depending on the year and trim level) *could* cause these kinds of widespread issues. This is the most complicated scenario, involving diagnostic tools and possibly replacement of the module.
What to Fix First (and How):
1. Check the fuses: This is the quickest and easiest step. It's always best to start here.
2. Check the bulbs: Rule out the simplest explanation before moving to more complex troubleshooting.
3. Inspect the wiring: Focus on the wiring harness near the taillights, brake pedal, and dome light switch. Look for any obvious damage.
4. Check the brake light switch: Relatively simple to access and replace if faulty.
Tools You Might Need:
* Test light or multimeter
* Screwdrivers (Phillips and flathead)
* Wire strippers/crimpers (if you need to repair wires)
* Replacement fuses and bulbs
* Wiring diagram (a MUST) – you can find these online through sites dedicated to car repair manuals or sometimes on forums dedicated to the 1985 Chevy Astro.
Complexity:
The complexity depends on the root cause. Fuses and bulbs are very simple fixes. Wiring problems, the brake light switch, and the BCM are progressively more complex, requiring more time, tools, and potentially electrical knowledge or professional help. If you're not comfortable working with car electrical systems, it's best to seek professional help from a mechanic. Attempting complex repairs without experience can lead to further damage.
