Technical


Miata Window Regulator Replacement (manual & power windows)
By John Kuykendall

Introduction
Replacement of the window regulator is usually required due to symptoms such as an inoperable or balky window. The causes may be broken regulator cables, malfunctioning regulator gearbox, lack of window guide lubrication or (in the case of power windows) a burned-out motor. To repair any of these problems, the same door and window disassembly is required. This repair may be undertaken by any careful, moderately experienced DIY mechanic, although it involves trim that requires care to replace neatly.

     

Step 1: This is a typical Miata door assembly. The inner panel shown is for a Miata with manual windows. Note that not all Miata's will have the same door panel - some earlier models may not have the door handles, map pockets, or they may have extra items such as arm rests. Models equipped with power windows will not have the manual window crank.

 
     

Step 2: Close-up of door, showing four Phillips or crosshead screws which must be removed. Two screws secure the door handle - the top screw is under a plastic cap that must be carefully pried out of the handle, while the bottom screw is exposed. The screw at the rear of the door/map pocket is under another cap, so pry this up (but not completely off, as it is attached) and remove the screw with the cap intact.

The final screw is a small one in the center of the door pull trim cup. Remove all screws and place the door handle and various parts aside. Note that there may be variations from year to year and model to model. Just make sure you have removed all the fasteners before trying to pry the door panel off.

 
     

Step 3: While holding the door pull open, remove the trim cup over the pull handle and set it aside. Note that in this picture, the door winder handle is already removed - see the next step for procedure.

 
     

Step 4: Manual Door Winder Removal: Using a door trim removal tool (available at Advance Auto and other places) or a thin rag or piece of string wrapped around the door winder crank, carefully remove the spring clip securing the crank handle onto the gearbox shaft. Don't lose the clip or the round plastic trim washer! You may have to pull the handle out smartly to remove the handle and clip. Set the handle and parts aside.

 
     

Step 5: Here's a shot of the window crank with the clip re-installed for illustration, and the round plastic trim washer that goes behind the crank handle. The regulator gearbox shaft is shown beyond, again in this case for a Miata with manual windows. Note that on some (older?) models with separate speaker grille panels, you will need to remove the grille prior to removing the door panel.

 
     

Step 6: Use the door trim removal tool (or similar flat tool) to release the numerous push-clips (about eleven on a typical Miata) holding the interior door panel onto the door. Most of these fasteners are around the outside of the panel, but a couple of them are in towards the center. Try pulling the panel out a little first, to visually locate the fasteners, so that you can pry as close to them as possible. If you encounter any resistance, check again to make sure you've removed all the screws fastening the panel to the door. Remove the door panel carefully over the door pull handle, pivoting the handle outward as necessary to clear the panel. Place the door trim panel aside where it won't get walked on!

 
     

Step 7: Door with the interior panel removed. Note that there is a clear plastic dust/moisture barrier under the panel, which is adhered to the door with sticky, nasty, very hard-to-remove black adhesive goop (mastic). You can fold the liner upon itself as you remove portions of it for access, thereby partially covering the goop and maybe preventing it from getting all over you - avoid it like it was poison ivy!

 
     

Step 8: Here's a shot of the plastic liner folded up and stuck together. Depending on your particular model and what areas you'll need to access, you may want to remove only portions of the liner, or the entire thing. Assess your particular situation and decide. Total removal means you will have to realign and re-adhere the liner when you're through, not a simple task!

 
     

Step 9: To remove the window regulator, you need to remove the window! In order to remove the window, you'll need to remove the black plastic window trim at the top of the door on the outside of the glass. First you must remove the screw or plastic pop-fastener at both the front and rear of the door. Roll the window all the way down (assuming this is possible with your broken regulator - you may have to manually work it down). Then CAREFULLY release each of the series of plastic clips along the top of the door by prying the tab inwards.

 
Use a padded, flat pry tool (like a small-bladed screwdriver wrapped with tape) working between the trim and the door over the top of the window, being careful not to scratch the paint. Avoid bending the trim piece (i.e., don't do what you see in the picture) in the process of removing it, keep it as straight as possible. A neat re-installation will be nearly impossible if you damage or bend this trim piece or break many clips. If this happens, you will probably have to purchase replacements (ask me how I know this). Removing this trim clears the opening at the top of the door for the window and other parts to be removed.
     

Step 10: Mark the location of the two 10mm window stop mounting bolts at the top edge of the door (#2 and #5, respectively, from the rear of the door). Use a "sharpie" or similar permanent-type marker to clearly mark around the heads of the bolts. You want to re-install the stops in the exact same location to avoid having to make window realignment adjustments later. Temporarily re-install the window winder and roll the window down so the top is about 7.5"up from the top of the door. Locate the three crosshead screws holding the glass to the window regulator, and remove them. Once removed, you can carefully lift the window glass as a unit up out of the door, and set it aside where you, the kids or your cats can't break it!

 
     

Step 11: Mark the location of the four 14mm nuts holding the window regulator to the door, by marking around the head of each nut with a marker. There are two nuts located near the top of the door (#3 and #4 from the rear of the door), and two on the bottom/center of the door. Again, you want to re-install the regulator in the same location that it was removed, to avoid later adjustments. Remove the three 10mm nuts (or two, in the case of power windows) securing the window regulator gearbox to the door.

 
Also remove the 10mm bolt on the bottom/front of the door, which secures the front window track guide, allowing it to be moved aside slightly for clearance to remove the gearbox. Unplug any connectors to the power window motor/gearbox. Pry the three push-fasteners that fit into holes in the door and secure the regulator cables. Now twist and work the regulator gearbox (or motor/gearbox) past the front window guide, and remove the entire regulator assembly (with cables and guides) through the large cutout opening in the side of the door.
     

Step 12: Here's the new (manual) regulator assembly, ready for installation. In my case, my manual regulator gearbox was starting to make "crunchy" sounds, like either some of the gears were broken or the cable was coming unraveled on the gearbox pulley. Power window regulators are similar, only the gearbox portion includes an electric motor and electrical connector. Oh, and another difference - the manual regulator assembly costs about $40 from Mazda, the power regulator about $250! If your cable breaks and you have power windows, you may want to look into replacing just the cable (not available from Mazda) with something like a bicycle or motorcycle control cable to save major bucks.

 

Install the window winder crank (or connect the regulator to connector in door) to check the operation of the new (or rebuilt) regulator before taking the trouble to re-install. Now, install the regulator in the reverse order as removed, being careful to match-up the marks made at the four mounting points. Check for free operation of the regulator again, and try loosening one fastener at a time if there is any binding, as the regulator may be twisted slightly. Be careful to reinsert the push-fasteners that secure the regulator cables and keep them away from the moving window. Don't forget to re-install the bolt holding the bottom of the front window guide.
     
Also, here's a shot of a typical Power Window regulator assembly, for those of you so equipped.  
     

Step 13: Clean the window of any accumulated dust, dirt and grease. Check the front and rear window guides and grease them with white lithium grease, as needed. The new regulator should come pre-lubricated, so just wind it up to a point where the window fastener holes are accessible through the door openings. Insert the window carefully into first the rear, then the front window guides. Work the window down until the three fastener holes line up with the regulator.

Reposition the regulator as needed. Make sure the plastic pads are correctly positioned on the window, and reinstall the three cross-headed screws snug but not overly tight. Align the two window stops at the top of the door where marked upon removal, and tighten the 10mm bolts. Check window operation again, by running the window fully up and fully down several times, checking for binding and noises. Loosen and move regulator mounting nuts slightly, one at a time, as needed to free up any binding. With the window fully raised and convertible top up, check for proper fit of the window along the weather strip at front, back and sides. Adjust as needed.

     

Step 14: Replace the plastic window trim at the top outside of the door neatly (GOOD LUCK!), making sure the trim snaps into the door by engaging each clip. Secure the front and rear of the trim using the push-fastener or screws, as applicable. Replace the door interior panel, speaker grilles, trim, handle, pull cup, and crank handle in the reverse order as removed.

Note that you insert the top of the panel into the door window gap first, then push the panel down until fasteners "snap" into place. You may need to lightly pound the panel down all over with your fist to make sure the fasteners snap into place, particularly in the center. The panel should fit flat and neatly against the doorframe along all edges. Check the window operation one more time, to make sure you didn't screw something up when you installed the panel! Clean up any stray black goop or grease, and you're done!

     

ADDITIONAL THOUGHTS ON REPLACING BROKEN POWER WINDOW REGULATOR CABLES:

Here's a common reason that many power windows on Miata's need repair - a broken regulator cable that prevents the window from being raised or lowered.

 
     

Apparently, Mazda does not sell a replacement cable by itself, so you must buy the entire motor/regulator assembly for about $250 per side! Assuming your motor/gearbox is still working fine, it is possible to replace just a broken cable without buying an entire new regulator assembly, but it requires a bit of ingenuity and patience.

A very detailed procedure for doing this is included in the Miata Enthusiast's Manual by Grainger, available from most Miata parts places (PBC, Finishline, Moss, etc.), and thus I've not attempted to cover it here. Replacement basically involves partially dismantling the gearbox and re-threading a new cable onto the motor drive and through the regulator. The ingenuity part comes in with finding an appropriate replacement cable (motorcycle or bicycle shop?) with the correct end fittings. But, it could save you a bunch of money. Good luck!!.