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Window motor rebuild - How to

40K views 73 replies 31 participants last post by  chevymaher 
#1 ·
Well I guess I'm the first to discover this, so I'm going to try my hand at making a 'how to' on it. Here goes.

It's pretty common to see people having issues with their power window motors, but now I know why. There is a resistor built into the motor unit, in series with the motor istelf. This is a temperature dependent resistor, where the temperature is determined by the current flowing through it. As the temperature increases, the resistance increases, allowing less current to flow. The problem is, these seem to get more sensitive as they age, resulting in the quite common "Motor stops working and I have to wait to use it again" issue.

All you have to do is bypass the resistor.

First of all, you'll need to get the motor out of the door. Follow your standard trim panel removal procedure (I use a crowbar) to get the trim off, and use a metal drill bit to drill out the rivets holding the motor in. You'll want to put some duct tape running up one side of the window, over the door frame, and down the other. This will keep the window from falling into the door when you take the motor out.

When you have the motor out, you'll need to crack it open. There are three metal tabs that hold on the plastic end cap, I found that a pair of large channel locks worked quite well for bending these.



Then carefully pry off the end cap. The whole thing will most likely be covered in a very sticky grease (marine grease?) that will give you some trouble in getting the cap off. Be aware that the motors brushes are attached to this cap and are under spring tension, so be patient and take your time if you don't want them to fly in all directions when you finally get it off.

Once you've finally removed it, the underside should look something like this:



That copper bar there with the numbers on it is the culprit. All you gotta do is put a dab of solder where the top bar is exposed to the bottom bar:



And just like that, it's fixed. But now comes the hard part: getting the motor back together. Initially I had tried to stick the stator back into the end cap with the brushes, and then stick all that back into the housing. I quickly found out though that the magnets on this thing are quite strong, and will just yank the stator straight out of the brushes. I did find an easier way though. Start by bending all the rear tabs on the brush mounts all the way out. Initially they should look kinda like this:



And you want them to look like this:



Now, you want to pull the stator out only enough to attach the brushes and end cap. But again you'll find that the magnets just want to yank the stator back down. What I did was I took a couple of flat iron bars (from a scrapped transformer) and stuck them down the sides of the housing, where there are gaps between the magnets. This was enough to hold the stator up, and I was able to remove them without disturbing the endcap.

Now you'll need to put the brushes back in. With the stator still pushed up and the end cap sitting on top, push the brushes through the backs of the brush holders. The brushes have a 45 degree cut on two sides, these sides need to go against the plastic end cap. Now put the springs in, and take a pair of pliers and start squeezing the end tabs together, just enough to put some tension on the spring. Push the spring towards the stator to make sure it is in all the way, and finish bending the end tabs back to their original position.



Remove whatever you used to hold the stator up (being careful not to dislodge the endcap), and push the end cap back down to its original place. Then bend the metal tabs back, and you're done!



It should be noted that this resistor was most likely a safety feature, cutting power to the motor when it was unable to move. This fix is done at your own risk.
 
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#27 ·
RECox286 said:
Hey CM,

You have to take into account that the auto reset c/b that comes with the truck is sized so that both windows will work at the

same time. When one of the window thermal switches opens, and since the c/b has not tripped, the other window will still work.

That is why I advocated a manual reset c/b sized to trip at slightly more than what the T/S is set for. (If that makes any sense.)

Bob
Yes I considering all possibilities.I am considering the breaker in the motor itself is to protect the windings which are more fragile than the van wiring.Seeing as the motor is not serviceable unless this procedure is done,that is a mute point.The wiring is protected by the breaker.That is my theory at this point.I wish my 90 van was still around I would go directly short the wires and hit the button see what really going on.Yes a in line fuse would be a good idea.What value would it be? With out having a guinea pig like my old 90 would have been.A guess is as usless as nothing if your wrong. The original poster never had a problem he messaged me.I have not so far.So I guess we the guinea pigs.Really if I had the value I needed I more than willing to put it in.I still working on it looking for the bi-metal switch value.I hear ya and I ain't thrown in the towel just yet.
 
#28 ·
Well, the P/W breaker, fuse, what ever is rated at 30A. So if you cut that in half, less the safety, which keeps the darned thing working

and not tripping, I figgure that it would be safe to, say, use a c/b rated at 1/2 the 30A plus maybe 5A less than that, or 10A .

Instead of shunting the two brass pieces with solder, solder a 10A manual reset c/b in paralell with the thermal switch and run the

wiring to a convenient location. With the motor in the circuit, and hooked up to the load (window) see if a 10A c/b trips out.

I'll bet it won't unless the motor shorts and fries, in which case the lower value c/b will be the protector. Of course it is just as

easy to replace the motor, because JY's are full of them. Even retail, they aren't that expensive, and they don't go bump in the

night every 2 weeks.

Bob
 
#29 ·
For the record, I'd like to say that the device being disabled here is most certianly not a bi-metallic strip. It may be difficult to see from the pictures, but the two bars are made from solid copper and are much too thick to have any mechanical action to them. It is also worth noting that during my initial investigation into what the fck was wrong with the goddamn thing that I applied heat to the joint with a soldering iron while measuring the resistance, and saw a steady increase rather than a sudden open circuit.

It is my opinion that this device was originally intended to only be activated in the event of a jammed motor (for example, the window is already all the way up or down), where the short circuit current would be sufficient to heat up the junction, increasing the resistance until it was so high that no more useful current could flow. I beleive that the failure lies within whatever compound is used between the two plates to create the thermo-resistor action. Either with age or use, the joint breaks down and becomes more sensitive, raising the resistance at ambient temperature. These few ohms of resistance are enough to generate heat during normal use, creating a positive feedback loop until, again, the resistance is so high that no useful amount of current can flow.

I hope this makes sense. :shrug:
 
#31 ·
Great tip, will save in the memory bank.

FWIW, I had a weird failure today. Opened up the port side door to fix what I thought was a bad tooth on the regulator or motor (window would raise and lower part way then stop moving and make a loud clicking sound).

On disassembly, I noticed the rivets holding the motor had been removed and replaced with screws (motor had been replaced before)...

The problem was in the motor assembly transmission... not in the regulator at all. I will save this one, since it has a good motor I may be able to use it to rebuild what ever one fails next time.

Posting just to possibly prevent someone else from trying to buy a regulator if they had a similar problem in the future.
 
#32 ·
This was a very interesting and informative post. As a 20 yr Navy Electronics/Radar Technician, let me add my '2 cents' :2: about tolerances, figuring out what size fuses, ckt. brkrs., resistors, etc. to use. In school I was always taught that engineers use a 35% 'overage' factor when computing electrical 'safety' ratings. For instance, if a ckt. brkr. is rated for 20 amps, it will probably handle 23-25 amps momentarily w/o 'tripping', and the interior parts will be designed to handle 30 amps without substaining severe damage, but the 'trip' mechanism 'trips' @ 20 amps, of course. Of course, when I went in the Navy, we didn't have any DVOM's, we only have VOM's!! Simpson 260's to be exact!! My friend down @ KDT Electrical Contractors has one sitting on his counter. They were designed to handle a drop of 5' & still stay accurate. In some cases, an analog VOM is more accurate than a DVOM, especially when looking for 'average' voltages, because the needle doesn't react as fast as that 'chip' does. Also, true amperage readings only come when your meter is 'in series' with your circuit, not when it's 'in parallel'!! Just saying :wave:
 
#34 ·
Seems reasonable on the ratings. Same things my brother an electrical engineer tells me.

But since we here again. I will give the hillbilly weather out the window report on mine.

Since feb we have discerned 2 things.

1 window still works like new.
2 Van hasn't caught fire yet.
 
#35 ·
Many thanks to the OP for this tip. I fixed my passenger side motor that was at a point that it would barely move an inch and it all went so well that I decided to do the driver side as it was starting to show sign of fatigue. Also want to thank Detroit_Dave for the twist tie tip..it worked like a charm.
 
#36 ·
this section proved usefull, being able to see what everything lookes like before hand means you can get through the job in record time. a plus for guys like me with little free time.
 
#40 ·
Got to put a piece of wood in there to hold the window up.
So it don't fall and possibly break, or slam your hand in there when your unawares.
Drill the pop rivets out. After you get in so far they spin.
Got to hold the drill bit at a 45 degree angle or so and let it chew the end off till it comes off.
I used a nut and bolt to replace it. Makes it simpler in the future to work on.
 
#41 ·
Argh.. damn frustrating to have a window that takes it's leisurely time getting back up.
It is cold here in Upstate NY for 6-months out of the year!

I will certainly look at the external circuit breaker idea in place of the in-line, embedded circuit breaker.

Herminator
 
#42 ·
I said I was going to do a circuit breaker to platicate the Nay-Sayers.
I had no intention of doing so because it has one in the fuse box already.
I roll my window down everytime I park it in the garage. So I can reach in when it down there.
I got 2 years in feb on my window motor rejuvination. Works like new still and I never had any problem. Even after having that side wiped out last year. I put that motor and track in the new door and it runs like a swiss watch. I thinking the redundant circuit breakers were not needed.
 
#44 ·
FWIW, I had a weird failure today. Opened up the port side door to fix what I thought was a bad tooth on the regulator or motor (window would raise and lower part way then stop moving and make a loud clicking sound).

On disassembly, I noticed the rivets holding the motor had been removed and replaced with screws (motor had been replaced before)...

The problem was in the motor assembly transmission... not in the regulator at all. I will save this one, since it has a good motor I may be able to use it to rebuild what ever one fails next time.

Posting just to possibly prevent someone else from trying to buy a regulator if they had a similar problem in the future.
I'm experiencing the same symptom. It goes down roughly and jerking to goes up with loud clunking noise. I've also noticed the motor had been replaced with screws instead of rivets. How do I fix the motor assembly transmission in this case?
 
#49 ·
I have a inop motor on the passenger window of my 1986 Astro van. I had decided to replace it with a used one from the pull-a-part. So I grabbed one the last time I was there. I hadn't took the time to change it simply because I was not sure the one I cut out of the junked van was in any better shape than mine. So I saw this string and decide to pull mine apart and check it out first.
The large copper piece is actually a bi-metal that warps slightly with temperature pulling them apart to open the circuit when too hot. If you look at carefully you will see two distinct pieces of metal running the length. The solder bridges the two so the input connection (from the wire harness) is directly connected to the respective brush.
The resistance of the connection between these two strips of metal over time increases when cold. I'm sure if you could clean the connections it would be like new. Perhaps a cleaning solvent would work. But the solder is the way I am going.
There are, as mentioned by Detroit Dave, two holes that are drilled through the end cap that line up with the center of the brushes. A stiff wire installed here would hold the brushes fully retracted while reinstalling the end cap over the stator.
I took the center copper wire from a scrap coax cable from the TV cable company. stripped it back for the stiff wire to hold back the brushes.
It worked perfectly, I didn't need to lift the stator up at all, it slid back together in a couple seconds.After I got it soldered and reassembled I measured the resistance across the wire harness input connectors and it read 1.1 ohms
 
#50 ·
I'm not an electrical engineer, but if you opt to bypass the resistor as being recommended here, I think you would be well advised to install a marine circuit breaker somewhere you can reset it if someone presses the window button too long. The circuit breaker should be just a bit more current rated than the normal current as I expect the current to increase and the breaker to blow. A current meter or clamp on current meter is a good tool for anyone to have in their toolbox these days. Many low cost digital voltmeters (DVM) have a built in current meter and the DVM can be bought at most home centers for $20 or more. I would guess that a 5 amp circuit breaker would protect your wires and still allow enough current to operate the motor, but without taking current readings I could be mistaken. The circuit breakers come in 5 or 10 or 15 amp at marine supply stores. Good Luck!
 
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