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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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#3 ·
Big_kid said:
Nice detail, nice pics. Maybe add an inline fuse or circuit breaker for some protection?
Yeah, that would work. But you'd blow a fuse every time some dope decided to hold the button while it was already all the way up or down.

I made this same fix to the motors on my door lock actuators a few months ago and have had no ill effects. In my professional opinion, there is very little risk. The worst that could happen is a motor winding would burn out with a puff of smoke, and you'd have to replace the whole unit.
 
#4 ·
I agree. A self resetting circuit breaker would do the job. If you used a fuse and someone held the button and blew it, you could then guilt them into thinking they broke it. I've done that in my wife's Villager when my nephew kept playing with the power window. he rolled it down & I hit the lockout button & told him he burnt it up and he'd have to pay for the $200 window motor. He never played with them again.
 
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#6 ·
Rey said:
Brilliant.

I wasn't aware of the existence of low voltage circuit breakers though. Tell me your secrets.
They do exist, and are not magical in any way. You can get them in the standard blade style fuse and they are generally black with no way to look at the fuse ( not translucent ).

Question would be, what would be sufficient to keep the motor from blowing the breaker, but low enough to protect it? 25amp?
 
#7 ·
What I'd really like to know, is how you discovered this fix in the first place. That's pretty heady stuff for the average mechanic to delve into and figure out if you aren't familiar with electric motors. My old grand am had a shift interlock solenoid that was actuated by the key that would over heat and not allow me to pull the key out of the ignition until I removed the interlock solenoid and essentially disabled the system.
 
#8 ·
There is no subject that is above any one of us. One only needs the desire or need to find stuff out, to over come a problem. This is the age of information.

Bob
 
#9 ·
RECox286 said:
There is no subject that is above any one of us. One only needs the desire or need to find stuff out, to over come a problem. This is the age of information.

Bob
This is truth, but it takes a certain something to trace things of this nature down, and then to do a tutorial on top of it to help others...epic win. I did similar when I was having a hard time with my OD switch started flaking out on me in my Dodge Dakota. It's on the end of the shifter and was a simple momentary contact switch. There were others who showed how to make the truck start with OD disengaged, but no one had done a write up about fixing a bad switch. Well, it wasn't a bad switch, it was just bad contacts and a little pencil eraser and a small shim took care of the problem forever. Personally, I have a moderate electronics background ( or as I like to say, enough knowledge to be dangerous ) so tackling it with blind faith wasn't as hard as it would be for someone who doen't know what a DVOM is.
 
#10 ·
Mostly, you will find that fixes are easier than getting the affected parts disassembled. Take for instance the horn switches on our newest truck; a 95 Astro.

If you are not really careful, the plastic back plate will shed its' little latching fingers, ergo: no more useful switch. Other than that it is just a matter of filing

the contacts, and being careful with the assembly. I have found this to be true of many of the parts that I have "fixed" on my "old" and obsolete fleet.

Of course I am old and obsolete too, so I guess that makes for an even sporting match. Ha. Well, sometimes you just gotta be persistant. I find that old

and persistant overcomes youth and impatience most of the time. Last thought: I didn't pop out of mother with a set of wrenches in my hand, and you sure

as heck didn't have a Multi-meter in yours !

Bob
 
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#11 ·
Since I've got the extra motor, I'm going to do so some tests to see what sort of current it draws, and how long it can endure being jammed. I figure 10 seconds at 14.4 volts would be enough to go without a fuse.
 
#12 ·
So, it seems a 10 amp delayed trip breaker would work well for this. At 14.4 volts, the unloaded motor drew about 2-3 amps, and voltage dropped to 12.3. With the motor jammed, current rose to 15 amps, but I held it for 20 seconds without overheating the windings. it probably could've endured it even longer, but I didn't want to risk damaging it.

So there you have it. A 10 amp slow-blow circuit breaker if you want to play it safe, however since it held up for a full 20 seconds, I don't think it's necessary.
 
#14 ·
Just a tip, if you have a multimeter you should use it to verify your solder joints. Measure the resistance over the joint, it should be less than one ohm. If the joint didn't connect, it will read somewhere around 10 ohms.

I can't seem to edit my original post, why is this? I've got some more info I'd like to add to it.
 
#15 ·
The edit button is only available for a limited time after a post is made. That's in the site's settings and moderators don't have access to it. Send your revisions via PM & I (or another global moderator) can add them.
 
#17 ·
Looks like the P/W fuse is rated for 30a. Fairly heavy ! This must be the reason for the thermal reset protection in each motor. Any chance of bridging the bad boy with a circuit

that includes a remote c/b instead of just shunting the components with solder. I'd be willing to bet that might be a better choice. It would involve a bit more work, but would at

least have a better chance of not smoke checking the motor. What is the amperage draw of a single motor under a stalled loading ? Easy to find out; jam the output gear while

trying to make it go electrically, while you have an amp probe in the circuit. Figure that there are 2 motors in the circuit, plus what ever else the fuse is hooked to, so, perhaps

a bit less than 1/2 of the fuse for one motor, say 10a ? Here's where the testing comes into play. Start with a 10a fuse, and start reducing values until the fuse smokes, then add

1/2 of the failed fuse as a safety factor. I won't say my logic is where it should be, I'm no rocket scientist, but it sounds like a place to start.

Bob
 
#18 ·
RECox286 said:
Looks like the P/W fuse is rated for 30a. Fairly heavy ! This must be the reason for the thermal reset protection in each motor. Any chance of bridging the bad boy with a circuit

that includes a remote c/b instead of just shunting the components with solder. I'd be willing to bet that might be a better choice. It would involve a bit more work, but would at

least have a better chance of not smoke checking the motor. What is the amperage draw of a single motor under a stalled loading ? Easy to find out; jam the output gear while

trying to make it go electrically, while you have an amp probe in the circuit. Figure that there are 2 motors in the circuit, plus what ever else the fuse is hooked to, so, perhaps

a bit less than 1/2 of the fuse for one motor, say 10a ? Here's where the testing comes into play. Start with a 10a fuse, and start reducing values until the fuse smokes, then add

1/2 of the failed fuse as a safety factor. I won't say my logic is where it should be, I'm no rocket scientist, but it sounds like a place to start.

Bob
Already done, see viewtopic.php?f=76&t=13637&p=145763#p145708
 
#19 ·
I might have missed it, but I don't think it was stated yet that the 'copper bar' that was soldered in the original post is the internal circuit breaker for the window motor. I have read that they get weak over time, and open up earlier than they should. But in the case of power windows, I'm convinced that they get more of a workout as the vehicle ages, because the window track gets rusty/dirty/scaly/whatever and makes the window slides bind up, causing the motor to draw more amperes. It's a real good idea whenever you are inside a door panel to slather some lithium grease in each of the three window slides (on each side of the rollers) to keep them from deteriorating. On most cars I've done this to, the window goes up & down noticeably faster.
Regarding the internal circuit breakers; they are put in to prevent damage to the motor from a stuck/welded switch or a kid with nothing else to do, etc. If you google 'window motor' and 'astro', you get a million hits, so the internal breaker must have been undersized from the factory. Nice write-up.
 
#20 ·
Thanks for sharing this handy-dandy How To!

I've been inside countless electric motors (these particular units are some of the cheesiest!) - and just wanted to mention that you'll occasionally find a sort of "helper" inside to reinstall the brushes. Sometimes they provide a little hole near the face of the brush holder, towards the commutator end, so you can load the spring & brush and insert a pin or piece of stiff wire to keep it in place for assembly. The clockwork-type springs can usually be wound tighter and pulled outward until they wedge the brush against the side of the carrier, until you're ready to let it slide forward. If you'd rather use a non-violent alternative on brushes which don't offer much help (like these), a couple of cheap twist-ties can save you a lot of grief. Nice fresh ones are found in every box of trash bags... one wrap around each brush carrier does the trick, and they're easy to slide out when everything is going back together. (On this window motor I used a popsicle stick to support the armature just below the commutator, then I removed the ties just before letting it fall into place)
***removed dead image link***
 
#21 ·
I have just completed the impossible corbonite maneuver.Whoever was involved in this thread they are Da Man.I was ask to go to the store.Got in the van.Humm window went up an inch and stopped.That's new.Well on the way to the store in the cold' it went up a inch at a time every couple minutes.Well I am stressed my baby is ill.Then I had a passing thought.
can't fix stupid.jpg

I remembered this thread and started studyin up Jethro Bodin style.
Well after grumbling about the door panels being impossible to get off without hurting them, I went for it.Only thing I did different was took out the stator assembly to get the brushes back on.Held the stator assembly with a pick while I fought the magnetic forces getting it back into the magnets.
I used Mass air flow cleaner on all the connections and brushes.Soldered that breaker joint.And greased the inside of the motor and the moving parts of the window track.Got it together and I was singing hallelujah.Works like brand new.Saved myself a heap of dough on a window motor Reckonin while I transpired. :character-willie:
 
#22 ·
[/1st let me establish my credentials: I was a 20 yr. Navy Electronics Technician. After retiring fm. the service, I continued applying my electronics skills as an Electronics/Computer Technician for Radio Shack, Tracor, Inc., & Bendix Field Engineering, etc. Even though I am 'officially' retired (again), I still dabble in doing washer & dryer repairs, electrical wiring repairs & installation, etc.

That said, I think what you are calling a 'resistor' in the window motor, appears to be more like a 'thermal disconnect', which is a 'Bi-Thermal' piece of metal. What happens here is when the motor draws too much current, this piece of metal heats up, bends, and breaks the contact, stopping all voltage/current flow, thus stopping the motor. When it cools down again, it remakes the contact, allowing voltage/current to flow again, until it overheats again. By soldering the end that opens when it heats up, you keep voltage/current flowing @ all times. This will work, until the motor overheats for once & for all, a wire or contact 'melts', etc.

Now that I understand this, it makes more sense to me, as I've noticed that my power windows tend to 'stall' more in warmer months, or on hot days, than in colder months/days.]
:2:
 
#23 ·
Yes it was a bi-metal strip thermal disconnect.Corroded high resistance across the connection.Brushes were full of burnt grease also causing bad contact,due to brushes not extending correctly.In turn the motor was drawing to much current due to the resistance causing it to open almost immediately.As long as the window moves overheating is not an issue.If the window locks/hangs up then you have a overheating issue.Fix the window track and don't lay on the button.Brushes next in line to wear out now.They were about half worn.
 
#24 ·
I believe I suggested that a manual reset c/b be wired into the line when doing this particular "rebuild" since what it does is to

shunt the thermal switch that is in the circuit. The T/S probably was put there in the first place for a good reason, No ?

Bob
 
#26 ·
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
 
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