1979 VW Van blowing fuse for left rear tail light and side marker and negative wire for these lights gets hot as well What could be causing this problem?

The issue you're experiencing with the 1979 VW Van could be due to a short circuit or a grounding problem in the wiring for the left rear tail light and side marker. A damaged wire, poor connection, or corrosion in the circuit can cause excessive current flow, leading to the fuse blowing and the negative wire heating up. It's important to thoroughly inspect the wiring harness, connectors, and the bulbs themselves for any signs of damage or wear. If necessary, consult a wiring diagram for troubleshooting and consider seeking professional assistance if the problem persists.