1. The Wiper Motor: This is the most common culprit. It could be seized, burned out, or have internal mechanical failure. You'll need to access the motor (usually under the rear cargo area, possibly requiring removal of interior trim) and test it directly with power (carefully, using a multimeter and appropriate voltage). If it doesn't spin, the motor needs replacement.
2. The Wiper Linkage: The motor might be working, but the linkage connecting it to the wiper arm could be broken, dislodged, rusted, or seized. Inspect the linkage for any visible damage or binding. This often involves removing the wiper arm to properly assess the linkage.
3. The Wiper Switch: While less likely since you say there's power, a faulty switch could be sending an intermittent or weak signal to the motor, or not completing the circuit properly. Testing the switch's output with a multimeter would determine this. This is usually a simpler and cheaper repair compared to the motor or linkage.
4. Fuses/Relays: Double-check the fuses and relays related to the rear wiper system. Even if you have power at the motor, a blown fuse or faulty relay could prevent it from functioning. Consult your owner's manual for their location and ratings.
5. Wiring: Look for any broken, corroded, or loose wires in the wiring harness leading to the motor and switch. This can be tricky to diagnose and might require tracing the wires. A multimeter can be invaluable here.
6. Ground Connection: A poor ground connection can also prevent the motor from working. Ensure the motor and its mounting bracket have a good clean ground connection to the vehicle's chassis.
Troubleshooting Steps:
1. Check fuses and relays: This is the easiest and quickest step.
2. Inspect the wiring: Look for any visible damage.
3. Manually operate the wiper arm: See if it's freely moving (this checks the linkage).
4. Test the wiper motor: This requires access to the motor and a multimeter. If you are not comfortable with electrical testing, this is best left to a professional.
5. Test the switch: This also requires a multimeter to check for proper voltage output.
Important Considerations:
* Safety First: Disconnect the battery negative terminal before working on any electrical components.
* Repair Manual: A repair manual specific to your 1994 Jeep Grand Cherokee will be extremely helpful in identifying the components, their location, and proper testing procedures.
* Professional Help: If you're not comfortable with electrical work or automotive repair, it's best to take your Jeep to a qualified mechanic. Diagnosing electrical problems can be challenging.
By systematically checking these areas, you should be able to pinpoint the cause of your rear wiper malfunction. Remember to replace parts with genuine or high-quality equivalents.
