1991-1996 INFINITI G20 Rear Window Regulator: Diagnosis, Amplifier Issues, and Replacement

Symptoms of a Failing Rear Window Regulator

When a window regulator in your INFINITI G20 begins to fail, the signs are usually obvious. Because the regulator is a mechanical part, failure often involves distinct sounds and behaviors.

• Grinding or Clicking Noises: If you hear grinding, clicking, or rattling sounds from inside the door when you press the window switch, it's a strong sign the regulator is failing. This noise is often caused by a frayed cable binding up or broken gear teeth on the drive mechanism.
• Window Drops Into the Door: The most dramatic symptom is the window suddenly falling into the door. This happens when the cable snaps completely, and there is nothing left to hold the glass up.
• Slow or Uneven Movement: A window that moves much slower than it used to, struggles to go up, or appears crooked in its track is a sign of a failing regulator. This can be caused by a stretched cable, increased friction in the system, or a broken guide.
• Motor Runs But Window Doesn't Move: If you can hear the window motor whirring or clicking inside the door when you press the switch, but the glass doesn't move, the connection between the motor and regulator is broken, or the regulator's cable has snapped.

Diagnosing the Problem: Regulator, Motor, or Amplifier?

For the 1991-1996 (P10) G20, a non-working window isn't always a bad regulator or motor. These cars use a separate "window amplifier" module for the driver's door, but issues with the master switch or wiring can affect other windows. Here’s how to narrow down the cause.

Step 1: Basic Checks

Start with the simplest things. Check the power window fuse to ensure it isn't blown. Also, make sure the window lock-out button on the driver's master switch isn't engaged, as this will disable the passenger and rear window switches.

Step 2: Listen for the Motor

This is the most important diagnostic step. Have a helper operate the switch for the failed window while you listen closely to the inside of the door panel.

• If you hear the motor trying to work (a whirring, humming, or clicking sound): The motor, switch, and wiring are likely good. The problem is almost certainly a failed mechanical regulator. The motor has power, but the broken regulator can't move the glass.
• If you hear absolutely nothing: The problem is electrical. It could be a bad switch, a failed window motor, or a wiring issue. On some 90s Nissan and Infiniti models, a failed window amplifier can also cause this symptom.

Step 3: The Window Amplifier Issue

Some owners have reported that a faulty window amplifier module can cause strange electrical issues, sometimes affecting windows other than the driver's side. If you have confirmed the motor is not getting power but the fuse and switch seem okay, this module could be the culprit. However, the most common failure remains the mechanical regulator itself.

Buying a Used Rear Left Window Regulator

For a vehicle of this age, a good quality used OEM regulator is often a smarter and more affordable choice than a new aftermarket part. The original Infiniti parts generally have better fitment and material quality. Here’s what to inspect before buying.

• Inspect the Cables: This is the most critical check. Look closely at the steel cables. Reject any regulator that has frayed, kinked, or rusty cables. A damaged cable is a failure waiting to happen.
• Check All Plastic Components: Examine the plastic pulleys and guide clips. After decades, this plastic can become brittle. Look for any cracks, stress marks, or pieces that have broken off.
• Verify the Motor Mounting Points: This regulator does not include the motor. You will transfer your old one. Ensure the threaded holes where the motor bolts on are clean and not stripped.
• Confirm the Part Number: If possible, match the OEM part number. The primary numbers for this part are 82721-50J00, 82721-50J05, 82721-50J15, 82721-50J16, and 82721-50J21.

Cost Comparison

Prices for a rear left window regulator for a 1991-1996 G20 can vary significantly. Note that aftermarket options often come as an assembly with a new motor, which you may not need if your original motor still works.

Replacement Overview (Difficulty: 2/5)

Replacing the rear window regulator on a P10 G20 is a straightforward job for a DIYer with basic tools. The entire process takes about 1 to 1.5 hours.

1. Remove the Door Panel: This involves removing a few screws (often hidden behind small covers in the door handle and armrest) and then carefully prying the panel off to release the plastic clips. Disconnect the window switch wiring harness.
2. Peel Back the Vapor Barrier: Carefully peel back the plastic weather barrier to get access inside the door.
3. Support the Glass: Use strong tape (like painter's or duct tape) to hold the window glass in the fully raised position. Tape it securely to the top of the door frame.
4. Unbolt the Glass: Locate the two 10mm bolts that clamp the window glass to the regulator's carrier bracket and remove them. The glass is now free from the regulator.
5. Unbolt and Remove the Regulator Assembly: Disconnect the electrical plug from the window motor. Remove the several 10mm bolts holding the regulator track and motor to the door shell, then carefully maneuver the entire assembly out through the large access hole.
6. Swap the Motor: Unbolt your old motor from the failed regulator and attach it to the replacement regulator.
7. Installation: Installation is the reverse of removal. Loosely install the new regulator, carefully lower the glass and bolt it to the new regulator, then tighten all mounting bolts. Test for smooth operation before putting the door panel back on.

Recalls and Technical Service Bulletins (TSBs)

As of this writing, there are no NHTSA recalls or TSBs specifically related to the window regulators on 1991-1996 INFINITI G20 models. Open recalls for this vehicle do exist for other issues, such as fuel filler tube corrosion and seat belt components.

Technical Specifications

Position: Rear Left (Driver Side)

Part Type: Regulator mechanism only, motor is not included.

Vehicle Fitment: All 1991, 1992, 1993, 1994, 1995, 1996 INFINITI G20 Sedan models.

Verified OEM Part Numbers: 82721-50J00, 82721-50J05, 82721-50J15, 82721-50J16, 82721-50J21

Frequently Asked Questions (FAQ)