A friend who owns a classic car repair business rang up for a customer with a window problem. The window would not go up to the top. The cause was obvious once the door card was removed (see how to do this below); the teeth on the gear were completely worn away. The reason this happens is that every time you open the door on a DB7 the window drops to clear the door seal, and it then moves back up again to complete the seal when you close the door. This repeated small up and down movement eventually leads to the gear wearing out. Then you are left with a large bill.

Figure 1 - Applying duct tape to cover the offending gap may help!

Figure 2 – Severely worn gears


Looking for a solution to this reoccurring problem I examined a spare regulator and decided that a new gear could be fitted. The main problem would be aligning the gear so that it would rotate freely. The original manufacturer used a jig and the gear is spot welded into position. After a few hours measuring and with quite a few paper patterns tried, I produced a drawing that I considered accurate enough to have the gears laser cut. This is a cheap process and can be done from a drawing in a standard PDF format. I added long side arms to help alignment, and ignored the gearing on the inside as it is not needed. The accuracy of laser cutting is not a problem, but the fitting and alignment of the gear plate could be a stumbling block.

Figure 3 – The prototype gear plate

I collected the prototypes a few days later and it was off to the garage where the DB7 was due in. The DB7 arrived with the driver side window sealed with duct tape, and it took about 1⁄2 hour to remove the regulator. Removing the door skin is simple. There are three large screws at the bottom of the door, and there should also be one small Philips screw on the front of the door. The inner door handle has a small Philips screw that needs removing and the plastic part gently eased back and out. The door pull has a hidden Allen bolt, which is under the rubber at the bottom, and has a nut that is accessed through the door shelf. Once these are all removed the door card lifts off. For the driver’s side you need to disconnect the cable to the wing mirror control. The inner window seal simply lifts off after removing the three large Philips screws. The next stage is to remove the door glass, which is fitted to the regulator by two 6 mm bolts. These should be loosened and the regulator slides released from the glass. The four bolts on the two window guides can then be removed and the glass should be free. It can make it easier to remove if you loosen off the nuts on the right angled brackets on the guides. The glass is removed by lowering it at the front and then drawing upwards to the rear.

The regulator is fixed to the door by five bolts – four in a rectangular pattern near the motor and one to the rear. Some can be hidden by tape, mastic or rubber bungs. Two bolts have slots and these can be left in, but loose – it makes replacement easier. The regulator then simply lifts out, disconnecting the plug from the door electronic control unit (ECU). When you plug the motor back in you will have to ‘lock’ the door by operating the latch with a screwdriver. This fools the door control ECU into thinking the door is locked and the motor will run both ways. The motor should run freely on the gears. If not the welds will need to be ground off and the gear moved slightly (we didn’t have to do this). An alternative way to operate the motor is to apply 12 V to the red and thick blue wires – reversing polarity reverses direction.

Figure 4 - The old gear is removed by drilling out through the four spot welds on the mounting plate. These holes will later be flood welded to fix the new part

Figure 5 - It is also a good idea to remove the motor and check the gears on the motor are not damaged. These ones are undamaged

Figure 6 - The new gear is put in place in the central position. The long arms ensure it is aligned correctly. Position it hard against the gear and then bring it back about 1⁄2 mm for clearance. Clamp it in position. Small tack welds are used to fix it for testing

 

The laser cutting process used on the gear plates actually surface hardens the tooth edge, so wear should be better than the originals that are stamped out.

Another window problem that can occur is that when the door is opened, it simply goes all the way down. This is caused by the window controller not getting a signal on the yellow wire that the window is moving. To fix this first check for a bent pin on the ECU/motor connector or a broken wire, then also check for a signal on the yellow wire. There should be a square wave present (6 V volts on a multimeter) when the motoris running; if not the sensor is faulty and the motor will need replacing. Having striped a motor down I have concluded that there are no user repairable parts. The motor is not available separately, but there should be lots available where someone has replaced their whole regulator.

If the door drops every time you open it, and does not go back up, then the window ECU needs reprogramming (see below).

Replacement of the regulator is the reverse of disassembly. You will probably need a magnetic tool to recover the window guides that will have fallen to the bottom of the door. Once reassembled, the window will need to be reprogrammed. Close the door, turn on the ignition, lower the window and hold the switch down for 5 sec, then raise the window and hold the switch down for 5 sec. The door should now drop a few millimetres every time the door is opened.

Figure 8 - Once aligned the holes should be flood welded to give a secure fixing. Some quick drying paint needs to be applied for rust prevention. Apply a generous amount of grease to the gears.

You can get a repair plate laser cut at your local manufacturer. I have put the drawing (DXF) file required by the laser cutting machine in this forum post.