How To: Repair Power Window

[Plastic Gears]

Twosrus sells replacement motor gears for power windows, which is a very common failure on the aging MR2s. However, the regulator gear could be the one causing your problems. This gear is irreplaceable and you must purchase a new regulator (either from Toyota, junkyard or another MR2 owner). Below is a great writeup from Ian which details replacing the regulator. But first, 86mister2 explains how to tell which gear is broken before tearing into your door panels.


Here’s how you can tell which gear is broken without dissasembly of your doors:

1) If the window pauses for a second but continues on its own to move up or down, it is a bad motor gear. What happens is when the motor gear moves to it’s bad spot, it obviously won’t turn the regulator gear untill the motor gear spins back to where it still has teeth. Then it will re-engage the regulator gear untill it comes to the bad spot again. This will cause the window to stop for a second or 2 each time it passes the bad spot, but will continue again on it’s own.

2) If the window pauses and doesn’t resume by itself, but just makes a horrible grinding or repetitive clicking noise and you have to give it a little push or pull to resume operation, you have a bad regulator gear. What happens is the motor will spin the regulator untill it hit’s the regulator gear’s bad spot. Since there are no more usable teeth on that spot of the regulator gear, the motor gear will just keep spinning against it causing the grinding noise and the window stops moving. When this happens, you need to give the window a little help so that the busted regulator gear turns enough to re-engage with the motor gear with its remaining teeth. This scenario IS NOT REPAIRABLE with twosrus gears.

3) Another problem that can happen which will lock the window in place would either be a power failure, or the window cable gets wrapped around a piece of metal. There is normally a little plasitc piece on these metal tabs that the cable rests against so as not to get intertwined with anything. Over time, the plastic tabs can pop off or break. If this happens, the cable may slip around the metal tab that once held the plastic and jam the window. Repeated attempts to raise or lower the window in this scenario may damage your cable, causing it to start to fray or snap. If you believe this could be your problem, I would recommend removal of the door panel and checking it out to make sure the cable isn’t stuck on anything.


Before starting the job, you should consider the possibility that not only the motor drive gear teeth are broken, but the regulator gear may be broken, too. You may need the complete regulator. It happened to me. I found very useful a screw-driver with replacement bits, including hex and star drives, particularly if it’s a ‘T-bar’ type. A square drive mm. socket set with a 3 inch extension is also nice. The BGB is very helpful, but is unclear on a few fundamentals.

[click to enlarge]

  • First, you need to be able to move the glass to different positions while you are removing components. (O.K. I know that, at this point, it’s broken, but…). You will need to have the window switch separate from the door trim. It’s only held with two screws and is easy to remove and replace in the door trim panel. The relay is also re-sited after removal of the door trim. This is because the window needs to be all the way down to remove the outside weather-strip from the door and mid-way to separate the window glass from the regulator.
  • Secondly, and most importantly, the plastic 6mm hex socket in the large toothed wheel of the regulator will not move the wheel (and the regulator) when the electric motor is attached.
  • The green manual (BGB) is not really clear about window adjustment, particularly with the 4mm hex drive in the regulator bolts.

The immobility of the regulator gears is quite reasonable, when you think about it. The glass must remain in any position, where it is stopped. The importance of this point is that you must position the regulator in mid-position with the 6mm hex drive before attaching the electric motor so that you can bolt the glass to the regulator through the holes in the door. You do this positioning as the motor is attached again to the regulator, after replacing the broken gear wheels and before the regulator is replaced in the door.

If you attempt to move the power window mechanism without the glass, then you will break something. I recommend disconnecting the battery, so that every time you supply power to the window regulator, it is intentional. When you remove the window relay and mirror power cable, the connectors are fairly obvious.

1) Generally, the green manual (BGB) is clear on the window removal process. They advise you to remove the door-trim, but don’t mention the tendency for those little plastic discs that cover the three screws to fly everywhere in car or garage. I suggest using some electrical tape over each as you lever it out with your taped-over screwdriver. They also don’t mention the need to remove a small screw from the plastic inside handle trim to get the door liner off. The water-proofing plastic liner to the door can gently be pulled off its tarry glue, after removing the power-window relay.

[click to enlarge]

2) The rubber mouldings at each end of the door can be detached by removing their two screws and the two screws that fix the outer weatherstrip are fairly obvious. If, like me, you drop any of them in the door, they are small enough to push to the door drain hole and fall through it.

[click to enlarge]

3) The rear-view mirror and its triangular lower frame will need to be removed from the door. The frame is fixed with two bolts, outside, and one nut, inside. Note the room for movement, allowing this frame to be adjusted to the position of the window-glass and prevent those annoying whistles at speed.

4) The manual says to remove the inside door handle and its links to the lock, but later implies that the regulator can be replaced with the door handle mechanism in-place. I managed to remove the regulator and replace it without removing the inside door handle, but removing it will give you a little more room, especially if you feel the temptation to be forceful. There have been complaints that the regulator channels and metal parts are weak and that bending any of these causes permanent damage.

[click to enlarge]

5) At this point I recommend the use of white paint (I used typing correction fluid, White-Out) to mark the present position of all regulator adjustment bolts and window stoppers and trim supports.

6) There are two glass stoppers to determine the final height of the closed window-glass; one is two inches from the rear view mirror and the other is above the door lock. Both are on the inside and are marked by a 1.5 inch oval defect in the metal. You can check the location by looking for two plastic hooks in the window glass that fit into the window stops.

[click to enlarge]

7) There are two door trim supports with felt that hold the window-glass against the outside weatherstrip. They are bolted to the inside panel of the metal and are more central in position at the top of the door than the door stoppers. The green manual (BGB) does not make a clear distinction between stoppers and door trim supports. The difference becomes important at the window adjustment stage after re-installation. There are 4 plastic clips in the door; 2 hold cables in the regulator and 2 position the power-cable to the mirror.

[click to enlarge]

8) Once you have marked the position and removed the window stops and felt supports, you can remove the bolt and 2 nuts that hold the window glass to the regulator. It is fairly easy to remove. Note the plastic-tipped metal hook that goes in the channel of the regulator frame nearest the door hinges. You will need to relocate that hook when you reassemble the window. Removing the 4 large nuts that hold the regulator channel arms and the smaller three bolts that hold the gear wheel assembly to the door will permit removal of the regulator. Check that you have unplugged the power connector, first. The regulator does come out, but it’s a bit difficult although it should come out without the use of any force. The door space is not equal throughout and, by looking, you can choose the widest space for each particular component as it presents on its way out. Here, midwives and obstetricians may have a particular advantage.

[gears] [motor]

9) The motor can be disconnected by removing the three screws that hold it to the regulator gear holder. The screws have star-shaped sockets and you must have the right size, because these are hard to undo and have to be tight. If the motor gear wheel is the only component with missing teeth then you are lucky. Otherwise you will have to fit a new regulator. Both gear-wheels are plastic. The Toyota part comes with all gear wheels and the smaller is a better fit to the 7 toothed metal motor drive than is the MR2 club part that is available separately. Both will be a tight fit and may need to be lightly tapped in with a plastic faced hammer.

10) Assembly of the window mechanism is the reverse of its dismantling, except for the nuts that go to the upper studs of the regulator; these, like the bolts for stoppers and felt supports, are only finger-tight. You must remember to adjust the height of the window-glass mounts so that you will see them through the holes in the door. The spring mechanism is designed to help take the weight of the door and if you screw on the electric motor without pre-positioning, the window will be at the top and its holding bolts, inaccessible.

[click to enlarge]

11) Fold the regulator without twisting or overly forcing distortions in the cables. The cable to the motor drive lies on the inside of the car, relative to the rest of the regulator. Note that it is attached, by a plastic clip, to the inside of the door. All cables will perform badly when distorted, ask any motorcyclist. You will need to be patient as the regulator goes back into the door, it takes lots of tries.


Adjustment of the Window

[channel and window as lever]


  1. Locate the studs of the regulator in their respective holes in the door and tighten the nuts to finger-tight at the top and fully at the bottom. Use your earlier paint marks to site things in their original positions.
  2. Hold the motor assembly so that the hex drive in the center of the gear is visible through the round hole, presumably for the handle in non- power-windows. The three nuts that hold it can be seated and tightened fully.
  3. Replace the front lower frame that holds the mirror, but do not tighten the nut and bolts. It will be moved so that there is no air-leak between it and the final position of the window glass.
  4. Put back the door stops in their original position and replace the external weatherstrip and the rubber belt moulding, being careful not to drop any of the 6 small screws into the door.
  5. Reconnect the power and raise the glass to its mid-position. Here, in theory, the window trim at the top of the door and the trim supports will operate at the mid-point of the curve of the window-glass.
  6. Adjust the felt covered door trim supports so that the glass is gripped between the elastic pressure of the weatherstrip and the felt door-trim supports (2). There must be a small gap between the felt underneath the rubber edge on the weatherstrip and the glass. The purpose is to use the elasticity of the weatherstrip rubber and not to grip the glass between the felts on both side of it. That way lies motor burn-out.
  7. The door trim supports can then be fully tightened. They, and the outside felt in the weatherstrip, will act as the fulcrum for the lever that is the window glass in its final position against the rubber around the door way.
  8. Raise the window glass to the top to ‘close’ the window, but do not close the door. You will need to check the height of the door relative to the roof side weatherstrip and roof drip moulding. The green manual specifies a 1 to 4 mm gap between top of glass and roof drip moulding. They say to remove the weatherstrip to check this, but you can get a working approximation by comparison with the other side, provided that no-one has changed it from the factory set-up.
  9. Note the distance of adjustment needed and lower the window. Adjust the height of the door window stoppers to bring the top position of the glass to within the specified distance from the roof drip moulding. Several tries may be needed. Finally tighten the bolts on the door window stoppers.
  10. The position of the window glass can also be adjusted by changing its position in the moveable mounts at the bottom of the regulator.
    1. The two nuts near the door lock allow the glass to be moved forward. The green manual specifies a distance of 7.5 to 11mm from the glass of the closed window to the center pillar moulding, behind the door.
    2. The nut nearer the door hinge permits the window to tilt as it rises. The green manual specifies that, when closing, the front of the window stops first and the rear rises a further 5-10mm. I had no trouble, but I wonder if there might be a need to adjust the door window-stopper positions twice if the window doesn’t move as expected.
  11. If you have a new regulator or the window position has been changed, you will probably need to adjust the prominence of the studs that hold the upper parts of the regulator channels. The alignment of the final position of the regulator with the door will have been done with the usual Toyota efficiency at the factory, but there is sufficient variation door-hanging to allow the possibility that the raised window may not exactly match the line of the roof moulding.
    [hex-bolts in upper regulator]
    You may have noted that the upper regulator studs have a flange on them which holds the glass against the upper nut. By screwing or unscrewing these studs, the regulator channels are tilted and the window glass can be made to tilt at the top of its travel. To do this you will need a 4mm hex drive. The window glass acts a lever with the regulator fixing at one end and the roof moulding at the other. The final position of the top of the glass can be made to tilt in towards the rubber by unscrewing, anti-clockwise, the bolts to move the lower end of the window outwards. Conversely to get more clearance at the top of the glass, when the door is closed, the studs need to be turned clockwise. With each set of two studs at the top of the regulator, you must make the same degree of rotation. Also move each pair of studs to the same degree. This implies that the tilt of the window in the door is correct. If the final tilt is wrong with more clearance at front or back, then adjust one set of two studs. If you do not move the two studs together, then, theoretically, you will stress and break the glass. More probably, you will merely incrase the friction in the channels of the regulator. A “T-bar” screw-driver is particularly useful to measure the degree of rotation.
  12. When you think you’ve got it right, tighten the appropriate nuts and bolts to fix their position.
  13. Before you finish, you’ll need to make a check of window movement with the door closed, particularly to check if the window tends to roll-up the soft rubber sealing weatherstrip.
  14. Reposition the front lower frame that holds the mirror, so that there is no air-leak between it and the final position of the window glass. Tighten the nut and bolts.

Once the window is done, the replacement of mirror, the installation of plastic seal, door trim and replacement of relay and switches is a straightforward reverse of dismantling.

Hopefully, you will have working window with relatively silent dry motoring.

This documentation in no way replaces the Toyota MR2 Repair Manuals. The purpose of this content is only to provide supplementary information to fellow MR2 enthusiasts. Midship Runabout and its contributing authors will not be held responsible for any injury or damages that may occur as the result of practicing any of the methods or procedures described within this website. Article and photo submissions are property of the contributing author.

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