How to Remove and Replace Rear Door Lock Assembly on a 1999 VW Golf Project Car TDI


Sometimes a rear door lock on a MK4 Golf or Jetta can be fixed  for less than $5.00. The TDI Guy shows you how-to fix-it-yourself and save big bucks on professional repairs. This new procedure is coming to you by wire from ( Darell's VW TDI Repair Maintenance Page) released  on 10/23/2008

Note:  To view a larger image of a thumbnail go to: URL: (Project 36).


The Project Car TDI was bought as a used vehicle with 200,000 miles on the odometer. It has a number of issues that have to be repaired. The rear door lock was one (!) of the issues that needed repair.
A door that won't open or won't close properly is usually caused by a defective door lock assembly. There are no repairable parts available from VW for this assembly. In this area, the door lock assembly, as a piece part, is not available at salvage yards we contacted. It is replaced as an assembly.
Interior lights that stay "ON" or trigger the alarm system at random, in most cases, are caused by a defective micro-switch that controls the alarm system and interior lights. The steps to check and replace the switch (not a recommended VW repair) are discussed in this procedure. Figure 36-1 shows a typical door lock assembly that is used on MK4 Golf's and Jetta vehicles.
Removing and replacing a defective door lock assembly is a very challenging repair. It is a tight fit in the door and difficult to access for removal. Removal and replacement steps are discussed in Rear Door Lock Assembly Removal of this procedure.
Figure 36-1 Typical MK4 Golf and Jetta Door Lock Assembly
The steps that the TDI Guy used to remove the door handle assembly on the Project Car TDI are discussed below:
  • Heat the door seal with a regular hair dryer to soften the rubber material.
  • Push the door seal away from door edge to access door handle mounting bolt.
  • Pull the door handle to the "open" position and hold in that position using an assistant.
  • Using a T-20 torx screwdriver, unscrew the mounting bolt two (2) complete turns to release the lock cylinder housing. Figure 36-2 shows the lock cylinder being released.
Do not remove the door handle mounting bolt. Only loosen. Removal of the bolt would require removal and realignment of the door lock assembly.
Figure 36-2 Releasing Lock Cylinder
  • Remove lock cylinder trim cover with a non-marring trim tool or a small flat-blade screwdriver (Figure 36-3).
Figure 36-3 Removing Lock Cylinder Trim Cap
  • Remove the lock cylinder cable clip from door handle lock release with a hook pick or a small flat-blade screwdriver. Figure 36-4 shows the cable being removed from the lock cylinder.
Figure 36-4 Removing Cable Clip from Lock Cylinder
  • Position the lock cylinder at a right angle and remove from door.
  • Pivot and remove door handle out of door.
The rear door panel has to be removed to access the door lock assembly. Project 9 on this Site shows the steps to remove the panel.
The door assembly carrier is comprised of several piece parts; namely, window regulator, door glass, door speaker, and door lock. The door lock is accessed once the carrier has been removed. For door lock removal, the rear door window and rear quarter panel must be removed.
  • Using a flat-blade screwdriver, pry out sealing plug in door assembly carrier to gain access to window glass securing bolts (Figure 36-5).
Figure 36-5 Removing Sealing Plug in Door Carrier Assembly
  • Energize door window switch and lower window until spreader plug and pin is visible in the removed plug cutout in window regulator.
  • Position a 5mm (3 inches long) bolt into spreader pin and pull pin out from spreader pin (Figure 36-6).
Figure 36-6 Threading Bolt into Window Spreader Pin
  • Thread an 8mm (4 inches long) bolt into the spreader pin.
  • Pull spreader plug out from window guide. Use a flat-blade screwdriver to move regulator cable out of bolt path. Figure 36-7 shows the spreader plug removed from window guide.
Figure 36-7 Spreader Plug Removed from Window Guide
  • Use a hair dryer to heat the window frame seal.
  • Pull window seal  toward front of window (Figure 36-8).
Figure 36-8 Pulling Window Seal from Window Frame
  • Using a flat-blade screwdriver, remove the cover cap to access quarter window frame mounting bolt (Figure 36-9).
Figure 36-9 Removing Cover Cap to Access Window Frame Mounting Bolt
  • Using a flat-blade screwdriver, lift the locking tab at bottom of quarter panel window frame (Figure 36-10).
Figure 36-10 Lifting Window Frame Locking Tab
  • Remove the window filler piece below locking tab (Figure 36-11). The filler piece supports the glass in the window frame.
Figure 36-11 Removed Filler Piece of Window Frame
  • Heat the window seal with a hair dryer to soften the rubber material before attempting to remove.
  • Starting at a corner, use a trim tool or fingers to remove the window seal from the door flange (Figure 36-12).
The window glass does not have to removed. Support the glass in the "UP" position with masking tape or equivalent to prevent damage to the glass from falling.
Figure 36-12 Removing Window Seal From Door
  • Lift the window frame by pulling upward. Pull the frame out from the front of the door (Figure 36-13).
Figure 36-13 Window Frame Removed
  • Pull the rubber boot that is mounted in the cutout in the rear door. The door wiring harness is routed through the boot from the "B" pillar (Figure 36-14).
Figure 36-14 Rubber Boot That Houses the Wiring Harness
  • Disconnect the wiring harness connectors (Figure 36-15)
Figure 36-15 Wiring Harness Connectors
  • Remove eight (8) bolts using a 3/8-inch square drive 10mm socket and a 3/8-inch square drive ratchet securing the door carrier (Figure 36-16).
Figure 36-16 Removing Bolts to Door Carrier
  • Using a 3/8-inch square drive ratchet attach a 3/8-inch square drive deep socket. Insert a 10mm 1/2-inch 12- point metric internal wrench into deep socket. Remove mounting bolts to door lock assembly (Figure 36-17).
Figure 36-17 Removing Mounting Bolts to Rear Door Lock Assembly
  • Bridge a flat-blade screwdriver between the door carrier and door assembly.
  • Rotate screwdriver or trim tool to loosen caulking sealing the door for removal of door carrier assembly (Figure 36-18).
Figure 36-18 Loosening Caulking Sealant for Removal of Door Carrier
  • Pull electrical wiring to various switches from boot in door.
  • Remove wiring clips from reinforcing plate in door.
  • Pull forward and remove door carrier assembly and door lock attached to carrier  (Figure 36-19).
Figure 36-19 Removing Door Carrier Assembly and Door Lock Assembly
  • The retaining bracket is riveted to the door carrier assembly. An electric or cordless drill is used with a 5/32 bit to drill out the rivets (Figure 36-20).
Figure 36-20 Retaining Bracket in Door Carrier
  • Disconnect inside release cable from clip on assembly carrier. Pry door lock off assembly carrier using a flat-blade screwdriver (Figure 36-21).
Figure 36-21 Cable Release on Door Lock
  • Disconnect door lock rod by turning rod in a clockwise direction (Figure 36-22).
Figure 36-22 Door Lock Rod on Door Lock Assembly
The door lock micro-switch can only be checked with the door lock assembly removed from the door. It is not an approved repair by VW. The switch is assembled in the door lock assembly and can only be purchased as an assembly.
When the door handle is pulled open, a ramp on the cam of the door lock presses the button on the switch to the down or closed position. When the button on switch is closed the cabin interior lights will be "ON".  The function of the micro-switch is to activate a circuit to the alarm system, interior, and dome lights. When the interior lights won't come "ON" or turn "OFF", the switch is the first culprit to troubleshoot. Also, if the alarm system activates itself in the middle of the night the micro- switch should be suspected as being faulty.
Use a digital multimeter (DMM) to check for B+ voltage to the door lock harness connector. Figure 36-23 shows the six (6) pins to the door lock electrical plug. With the ignition switch "ON" there should be 12VDC at pins 1 and 6.
Figure 36-23 Door Lock Electrical Plug Pins
The switch is housed in the base of the door lock assembly. Remove by following the below steps:
Servicing the micro-switch is a DIY repair. It is not covered in the Bentley or VW factory service manual.
  • Use a flat-blade screwdriver to remove the clip securing the switch to the door lock assembly (Figure 36-24).
Figure 36-24 Clip Removed From Door Lock Assembly
  • Lift the switch tabs "UP" from the two mounting holes in the door lock assembly (Figure 36-25).
Figure 36-25 Removing Switch From Door Lock Assembly Mounting Holes
  • Push the button on the switch to the down position with a finger. The switch should have a clicking sound. This would mean that the switch is "making" and "breaking" (Figure 36-26).
Figure 36-26 Micro-Switch Mechanical Check
  • The above check is only a mechanical check. The clicking test does not determine that the switch is fully functional. A diagnostic test for switch continuity should made with the DMM. Figure 36-27 shows the DMM being used to check for the switch "OPENING" and "CLOSING". The DMM showed that the reading on the display "OL" is open (button up). In this position with the button "UP", the switch is good as no current can flow.
Figure 36-27 Using DMM for Checking Micro-Switch Continuity
  • Figure 36-28 shows the DMM setup to check continuity with the button "down" or closed. The DMM showed that the reading on the display of the DMM is approximately "0". This would indicate there is switch continuity in the closed position. This test confirmed that the micro- switch is not defective and fully functional.
Figure 36-28 Checking Micro-Switch With DMM for Continuity
A visual check of the door lock assembly showed that the ramp on the cam assembly is worn (Figure 36-29). When the door handle is fully opened, the button on the micro-switch is "closed" (button down). In that position, the interior lights will  be "ON". With the door handle fully opened on the Project Car TDI, the interior lights did not come "ON". To fix the problem, the door lock assembly will have to be replaced.
Figure 36-29 Worn Cam on Door Lock Assembly
When the micro-switch has been determined to be defective, there are two (2) versions of switches that have been used by VW for applications on MK4 rear door locks.  Both switches are SPST  with blue and red colored wires. Each are mounted differently in the door lock. The procedure for checking the switches with the DMM are the same for each switch as discussed above.
For clarity, let's call these designs: (1) Early style and (2) Late style . A Dremel tool with a burring bit is used to enlarge the hole so that the old switch can be removed (Early style). A new replacement switch can be ordered from the Surplus Sales website. It can also be ordered from the Radio Shack Web Site or local retail outlet.  Ask for switch P/N 275-016A. The new switch is mounted to the door lock assembly using two (2) 10/32 x 1 inch machine screws and nuts. The blue wire is soldered to the common terminal of the switch. The red wire is soldered to the "NO" terminal
Check for the correct polarity with a DMM before installing the door lock assembly in the rear door.
The late style micro-switch mounted to the door lock assembly is being checked and discussed (above) in this procedure.
When the micro-switch has been diagnosed as being defective on the late style door lock assembly , you will have to become creative. The switch installed in the door lock is a special design and made especially for the MK4 door lock assembly. It has no part number on the switch. It is, also not available from an Internet site or a VW parts center as a piece part.
A salvage yard that specializes in European imports ,in your area ,would be a possibility for a late style door lock assembly. They do not sell piece parts, as a rule.
Your only other hope is to check with a service manager at a VW dealership. Tell him that you need a defective door lock assembly from a MK4 Golf or Jetta. This is a common repair on MK4's and all discarded parts are thrown in the trash can. Depending on what mood he is in that day, all he can say is "yes" or "no" to your request.
 If the above possibility does not pan out, you can order a new rear door lock assembly from the VW parts center for the sum of $193.00 US dollars. Ask for P/N 3B4839016AM.
The TDI Guy installed the new door lock assembly in the Project Car TDI using the following steps:
  • Re-attach door lock and inside release cable that was previously removed.
  • Attach door lock to door assembly carrier.
  • Install assembly carrier in the rear door.
  • Install the eight (8) door carrier assembly bolts and tighten to 71 ft-lb.
  • Route the electrical wiring through the boot in the rear door. Secure the electrical wires with clips that were previously removed.
  • Install the rubber boot between the door and "B" pillar.
  • Install the quarter panel window frame and door window guide in the reverse from which it was removed.
  • Install door window into door and insert spreader plug and spreader pin into window as discussed above.
  • Guide window into door.
  • Insert window into rail guides slot.
  • Position the window properly in the rail.
  • Energize door switch to check for proper operation of the window.
  • Install the door panel.
  • Hair dryer
  • T-20 torx screwdriver
  • Dremel tool
  • Deburring bit
  • Trim tool
  • Small flat-blade screwdriver
  • Large flat blade screwdriver
  • Hook pick
  • 5mm 3-inch bolt
  • 8mm 4-inch bolt
  • Masking tape
  • 3/8-inch square drive 10mm socket
  • 3/8-in square drive ratchet
  • 10mm 1/2-inch 12-point metric internal wrench
  • 3/8-in cordless or electric drill
  • 5/32-inch drill bit
  • Digital Multimeter