* Low Battery Voltage: This is the most likely cause. The clicking is the starter solenoid trying to engage, but it doesn't have enough power to overcome the resistance. The hum might be the starter motor itself struggling. Get your battery tested at an auto parts store to confirm its voltage and cranking amps. A simple jump-start might confirm this; if it starts easily with a jump, the battery is definitely the issue.
* Bad Battery Cables: Corroded, loose, or damaged battery cables can prevent sufficient current from reaching the starter. Inspect the cables at both ends (battery terminals and starter) for corrosion, looseness, or damage. Clean the terminals with a wire brush and baking soda and water solution, ensuring a tight connection.
* Faulty Starter Solenoid: The solenoid is the electromagnet that engages the starter motor. If it's failing, it might click but not fully engage the starter. This often requires replacement of the starter itself, as the solenoid is usually integrated into it.
* Failing Starter Motor: While less likely if you're getting a hum, a failing starter motor can still produce a clicking sound along with a hum as it struggles. It may be worn out brushes or other internal components. Again, this usually means replacing the whole starter.
* Poor Ground Connection: A poor ground connection between the engine block and the battery negative terminal can prevent sufficient current flow to the starter. Check the ground cable for corrosion and tightness.
Troubleshooting Steps:
1. Battery Test: This is the FIRST thing to do. A weak battery will exhibit exactly the symptoms you describe.
2. Cable Inspection: Check all battery cables for corrosion, tightness, and damage. Clean and tighten as needed.
3. Jump Start: Attempt a jump start from another vehicle. If it starts, it confirms a battery or cabling issue.
4. Check Ground Connection: Ensure a clean and tight ground connection between the engine block and the negative battery terminal.
5. Starter Solenoid/Motor: If the above steps don't solve the problem, you're likely looking at a faulty starter solenoid or motor. This usually requires replacement. It's often more cost-effective to replace the entire starter assembly rather than trying to repair the solenoid separately.
Important Note: Working on your vehicle's electrical system involves working with potentially dangerous voltage. If you're not comfortable working with car electrical systems, it's best to take your van to a qualified mechanic.
