* Wiring: The most probable cause is a problem with the wiring harness to the motor. Check the connections at both the motor and the switch. Look for broken wires, loose connections, or corrosion. A faulty switch is less likely since it's working for the up function. A partially broken wire in the harness could interrupt the down function but still allow the up function to work depending on the specific wire affected.
* Reverse Polarity: Although less likely with a new motor, it's possible the wires are connected backward. Double-check the wiring diagram for your specific year Camaro to ensure correct polarity. This is especially important if you had to splice any wires.
* Regulator: The window regulator is the mechanism that moves the glass. It's possible the regulator itself is faulty and is binding or broken in a way that prevents downward movement. The motor might be trying to operate, but the regulator is resisting. Inspect the regulator for any damage or binding.
* Switch (Less Likely): While the up function works, there's still a small chance a part of the switch is faulty. It's less likely if it's a brand-new switch but worth considering if other troubleshooting steps don't work.
Troubleshooting Steps:
1. Check all wiring connections: This is your first and most important step. Carefully inspect every wire and connection related to the window motor and regulator. Use a multimeter to check for continuity (if you have one).
2. Reverse Polarity Check: Consult a wiring diagram to ensure the positive and negative wires are correctly connected to the new motor. If you're unsure, disconnect the motor, trace the wires back to the source, and verify against the diagram.
3. Manually Test the Regulator: With the motor disconnected, try to manually move the window up and down using the regulator. If it's stiff or binds, this points to a regulator problem.
4. Test the Motor (Though Less Likely): You can test the motor directly with a 12V source (with appropriate safety precautions!), but only after steps 1-3 have been completed. Make sure you connect positive and negative correctly from a battery and use an appropriate amperage fuse.
5. Professional Help: If you're not comfortable with electrical work or mechanical repair, take it to a mechanic. It's better to have a professional diagnose the problem than risk further damage.
Remember to disconnect the negative battery terminal before starting any electrical work. Safety first!
