Thinking on modifying my car door locks to brushless - Page 1
Forum section: electronics / repair

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 07, 2023, 09:59:28 pm
content: My car is well known for its cursed door locks, the dreaded Mabuchi FC-280 motors die every 2-5 years.Although it's a bit random, some doors will fail a lot faster than others after replacing the motor, although they all do the same work.I blame it to Aliexpress quality but still better to change $4 twice than $150 in a new lock.I already fixed them several times, but eventually any of the 4 doors will break again.Then it's a f** mess, as the car tries to open the doors, one or more won't do so it'll close back.You might fight it but after several tries the system will shutoff the remote for a while.Of course I just ended using the feecking key, but it's a shame in winter with the wind, rain and all that, you want to get in/out fast!So I've been doing some research trying to find a compact brushless solution fitting inside the lock itself, needing minimal modification.Picturses of the door lock internals and the stupid motor:It moves a reduction gear that later spins a worm gear, so it requires very little torque.The central locking simply switches the polarity of the motor pins to close or open the lock.My idea is to pass them through a rectifier, then use one of the unrectified wires to detect the direction and toggle the appropiate control pin.A motor with built-in controller would be great, but I need it to be able to rotate in reverse.I've found some, but still too big: The 2412/2418 are 24mm wide...www.aliexpress.com/item/1005005389098818.htmlwww.aliexpress.com/item/1005002787368480.htmlSo far I haven't found smaller ones with integrated controller.The second option is to get naked motors, using a external controller.www.aliexpress.com/item/1005005368897031.htmlwww.aliexpress.com/item/1005005354667188.htmlBut the controllers I found either where too bulky, used some digital protocol or had no way to reverse the rotation.I ended researching a simple BLDC driver and making a little pcb using the DRV10974, fitting in 13x7mm.I know, I know, that cap-on-pin hack it's terrible, sacrifices to get it as small as possibleThe power will be about 2-3 amps at most, but only for2 seconds, I think the 1-Amp rectifier will survive that, not having time to heat up.The adventure continues....

author: wasedadoc
author_rank: Super Contributor
timestamp: June 07, 2023, 10:56:45 pm
content: They are not exactly the same as your photo but I've had similar problems with the front passenger and two rear door locks in my Skoda. The only one that has never failed is the one that has the fallback option of inserting the key!I've become quite adept at removing the locks, taking the motor out and cleaning the commutator and brushes, The really nasty one is the front pasenger lock as removing the door trim and carrier panel looks to be impossible if the door is locked shut because the dashboard prevents access to some of the trim clips and carrier panel screws.I took the precaution of intercepting the two motor wires in the loom behind the trim panel and adding extensions to bring them though the hole in the trim panel that is there for the electric window switch on the armrest/door-pull. The interior of the armrest/door-pull is easily accessed and in there I have put connectors so that I can disconnect the motor from the car's electrics and instead apply external voltage. A quick dab of 20 to 30 Volts persuades an incalcitrant motor to spin and unlock

author: Shonky
author_rank: Frequent Contributor
timestamp: June 07, 2023, 10:59:41 pm
content: What is the failure mode?Can you not just find a more reliable brushed motor of the same dimensions?

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 07, 2023, 11:05:29 pm
content: The contactor contaminates/clogs up and no longer makes good contact.Sometimes it arces and destroyes the motor, but so far I only saw that once, most simply had a thick layer of dirt.I think the problem is caused by the short working cycles, the motor startup current is high, the brushes erode faster, but the motor never has a good spin to clean the dust/crap.It's just 1/2 second, stop, 1/2second, stop...

author: lugaw
author_rank: Regular Contributor
timestamp: June 07, 2023, 11:19:33 pm
content: That's adding more point of failure and complexity to the system.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 07, 2023, 11:53:33 pm
content: These door locks are a problem on most older vehicles. The ones I own and work on have a different configuration, but the same basic idea. The failure mode on them hasn't been in the motor, but in the gear train, with dirt and dried lubricant increasing the friction beyond the motors capability. Clean and lube of the gear train solves the problem for a few more years.As an aside, one of these had a clever variation on the commutator design. Instead of the usual strips of copper parallel to the shaft the commutator was moved to a disk shaped pc board on the end of the windings. Gave a lot more surface area, so maybe less susceptible to contamination.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 08, 2023, 12:09:21 am
content: Quote from: lugaw on June 07, 2023, 11:19:33 pmWhy? It's the only failure in this locks. Every one I fixed looked brand new inside, full of fresh grease, no wear, perfect gears, nothing else than the motor.By removing the mechanical contacts, should finally last forever.

author: james_s
author_rank: Super Contributor
timestamp: June 08, 2023, 12:25:50 am
content: My 33 and and 38 year old Volvos have very similar door lock motors, I've had a wire come loose in one once but I've never had one of the motors fail, ever. Have you taken one apart to determine why yours are failing? The duty cycle is extremely low, even if the motor is only rated to last a few hours it should outlast the car in almost all cases.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 08, 2023, 12:47:08 am
content: I already said, the rotor contacts end with a layer of dirt.No damage, it's like hard, dark paint.There's no grease entering the motor, so it must be the carbon brushes, adding the fact the motor only rotates maybe 50 turns every time.

author: james_s
author_rank: Super Contributor
timestamp: June 08, 2023, 02:49:48 am
content: Maybe try to find a Volvo 200/700/900 lock motor assembly and adapt it to fit? As I said I've never had one fail and there have been quite a few of those cars in my family including a 240 my mother bought brand new in 1986 and still has.

author: amyk
author_rank: Super Contributor
timestamp: June 08, 2023, 03:47:42 am
content: Check the electrical system voltage. It might be shortening the life of the motors by being too high.If you're really inclined to mod it, I'd try to use a solenoid instead of a motor.

author: Whales
author_rank: Super Contributor
timestamp: June 08, 2023, 05:04:52 am
content: I think that either changing to brushless or replacing with a different model of brushed motor would both be good things to try. Go for whatever is easier to get your hands on.Trying to understand these small brushed motorsGetting datasheets for Mabuchi motors is hard. Sometimes you can find random ones on the web, but they're often for a slightly different model number compared with what you can buy or have (and I don't think consecutive numbers/letters mean models are similar). Perhaps they change so many params for each customer that each customer gets a unique model number?Try page 53 onwards of this doc (it's the biggest I've found):http://home.mlab.cz/Downloads/PDF/datasheets/Mabuchi_Motors_Complete.pdfNote the atrocious efficiency: many of these don't even hit n=0.5 at any point of their perf curves!I suspect that window door locks will use the absolute cheapest models possible, they have lots of gearing so they don't need to do much. There is a massive difference in performance (speed, torque, impedence, bearings) available in this one form factor. I've had some motors from an old fixed-wing toy craft that were amazin, some cheap Mabuchi's from Aliexpress that were pathetic and some mediocre greymarket ones from another site.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 08, 2023, 06:08:21 am
content: I'm also open to try a different motor, however it's almost impossible to know which one to get, all are sold as "high quality, long life, made with gold" and all that.With brushless, I know 100% it's going to last unless the electronics blow apart.

author: Psi
author_rank: Super Contributor
timestamp: June 08, 2023, 08:18:40 am
content: There's a few options.Those motors are a standard size, so getting a good quality version is probably the first thing to try.Another thing is to add like 6 diodes in series with the motor to drop the voltage 4.5V or so.I wouldn't put it past aliexpress to overstate the motor's voltage. And given this is a car the battery is at like 14V with the engine running, so you're already putting 2V more into the motors if the engine is going when they lock/unlock.And that assuming they could handle 12V to start with.Another option I would be tempted with is those Tamiya mini motors intended for those tiny race cars. See attached pic. Sadly they are 3V not 12V so you'd need some electronics to step the voltage down while keeping the fwd/rev control. Main reason i think they might be a good option is they are build with higher quality than your standard aliexpress motor and intended to be run hard albeit for a short time.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 08, 2023, 08:35:59 am
content: What is that standard size called?The 130 has same shape but it's 20mm.So far I only found those 24x18mm from Mabuchi.

author: Whales
author_rank: Super Contributor
timestamp: June 08, 2023, 09:52:29 am
content: I also call them "130" motors, but there are also lots of other model numbers with the exact same size (or the same cross-section but a different length). I'd love to know if there is a better name.Quote from: Psi on June 08, 2023, 08:18:40 amGood point. I know that some small brushed DC motors sound less happy and arc more at higher voltages (but I'm not sure if this is a universal rule). Perhaps undervolting them slightly might be good. They would be designed to work even with a somewhat flat battery, so there is probably a good tolerance range for operation.

author: Psi
author_rank: Super Contributor
timestamp: June 08, 2023, 10:28:43 am
content: Those motors are sold in a few different voltage rangesLike 3V 6V 9V 12V etc. and I would not put it past cheap manufacturers of them to decide to stop making the 12V version and sell the 9V one as 12V instead.Or maybe design a new 10.5V one that they believe and handle both 9V and 12V applications just to cut down on the number of sku's they need. etc...

author: sokoloff
author_rank: Super Contributor
timestamp: June 08, 2023, 11:24:14 am
content: I've changed about 6 of these actuators on my wife's 2005 CR-V (5 doors) in the last 11 years. I thought it was just a Honda fault, so I'm slightly relieved to hear other manufacturers having issues as well.Even with the prospect of changing each lock actuator every 5 or so years, I'd never spend the time trying to improve the part. The NRE time just won't ever come close to paying back.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 08, 2023, 06:07:19 pm
content: Well, lots of people are having this issue, havign to pay $150 every time.This car production ended in 2006, but there's still some people around with it.I guess it could be a small niche business, selling improved locks that won't fail.

author: sokoloff
author_rank: Super Contributor
timestamp: June 08, 2023, 06:29:31 pm
content: Ah. Mine are$15and 15 minutes to change.

author: wasedadoc
author_rank: Super Contributor
timestamp: June 08, 2023, 06:36:58 pm
content: Quote from: sokoloff on June 08, 2023, 06:29:31 pmThe item at that link does not include the motor and other bits.

author: coppice
author_rank: Super Contributor
timestamp: June 08, 2023, 06:38:29 pm
content: Quote from: sokoloff on June 08, 2023, 11:24:14 amRelieved is a strange term to use. You are content that if you get a different car next time, things will be just as bad?

author: coppice
author_rank: Super Contributor
timestamp: June 08, 2023, 06:45:36 pm
content: Quote from: james_s on June 08, 2023, 12:25:50 amInteresting. I'm pretty sure the Volvo 740 I bought 38 years ago, when they first launched, used solenoids for the door locks. It made a very solid clunk when the locks fired, and I had to service one of them. The little PCB that timed the pulse had an issue. I can't remember what IC they had on that board, but I remember it was a 0C-70C rated commercial part. That seemed very unsatisfactory for a car made in Gothenburg.

author: sokoloff
author_rank: Super Contributor
timestamp: June 08, 2023, 06:55:21 pm
content: Quote from: wasedadoc on June 08, 2023, 06:36:58 pmI assure you that it does. I installed one of that exact listing a few months ago.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 08, 2023, 07:46:10 pm
content: This motor looks pretty good to me... Any thoughts?https://www.aliexpress.com/item/1005002326133663.html

author: Psi
author_rank: Super Contributor
timestamp: June 08, 2023, 10:18:52 pm
content: Quote from: DavidAlfa on June 08, 2023, 07:46:10 pmThey do 'look' good quality yes, until you see the price. Seems a bit cheap to me.Makes me wonder if they assembled one very cleanly just for the photo.But at that price might be worth grabbed a couple just to tear apart and have a look.I guess the price is about double what the cheap ones go for, so maybe its fine.However, those motors are square in size and probably wont fit in your housing.Since that motor is 12-24V it should be totally fine at 14V in your car, which is a good sign.If you can make it fit it's probably worth a try.

author: Whales
author_rank: Super Contributor
timestamp: June 08, 2023, 10:27:34 pm
content: I wonder how the controller for these motors works?(1) Runs them until stall current detected. This could mean replacements with different impedances might not work properly.(2) Runs them for x seconds. It would be longer than necessary so that low-battery and high-resistance scenarios still lock. The motor would stall for a while, which might (?) cause brush and armature wear in one spot. Higher perf motors would stall earlier, lower perf motors later (or not at all).

author: Psi
author_rank: Super Contributor
timestamp: June 08, 2023, 11:08:50 pm
content: They probably use a little 'smart' single chip H bridge load driver IC with built in mosfets and current sense output.Then the main MCU just switches off once current hits a set point. Perhaps with a max time component as well.

author: wasedadoc
author_rank: Super Contributor
timestamp: June 08, 2023, 11:36:00 pm
content: Quote from: Whales on June 08, 2023, 10:27:34 pmI cannot answer for the specific locks that opened this topic but the Skoda ones (with VW logo and part number) whose inner workings I am only too familiar with have two internal microswitches which operate when the travelling mechanism driven by the lead-screw is in certain positions. They signal back to the control unit so I assume that is how the controller removes power when the lock and unlock states have been reached. There is a third microswitch which senses when the door is latched on the u-bolt on the door pillar..

author: james_s
author_rank: Super Contributor
timestamp: June 08, 2023, 11:47:34 pm
content: Quote from: coppice on June 08, 2023, 06:45:36 pmWe've had quite a few Volvos in my family with power locks, 1982 to 1996 and the actuators are all motorized, not solenoid. They do make a chunk noise and I assumed they were solenoids but then the one time one of them stopped working in my 740 I took it apart and was surprised to find it used a small motor very much like the one in the picture here and a wire had broken off it. If they ever made a lock actuator with a solenoid I'd like to see it but the one I took apart was definitely a motor. The gearing is quite aggressive and it traverses rapidly making a chunk sound when it hits the end, IIRC there is a friction clutch in the gear train.

author: amyk
author_rank: Super Contributor
timestamp: June 09, 2023, 01:56:17 am
content: Quote from: Psi on June 08, 2023, 08:18:40 amAs someone else has mentioned, those are 130 size motors, but the one in the OP's locks are 280 size - a bit bigger.Quote from: james_s on June 08, 2023, 11:47:34 pmNot sure about Volvos, but early GMs definitely used solenoid lock actuators:Look at the size and construction of that thing... and it's not surprising why they switched to motors, first with reasonably large metal-cased motors like this:http://www.aaignition.com/wp-content/uploads/2018/04/GWA164.jpg...before moving to the tiny rectangular 280-size motors in OP's locks, and apparently some of them actually use 130-size ones too.

author: james_s
author_rank: Super Contributor
timestamp: June 09, 2023, 07:41:24 pm
content: This is a lock motor I salvaged from my 1987 Volvo 740 after it got rear ended and totaled. As you can see, it's clearly a motor and quite a large chunky one that draws several amps. It actuates quickly and makes a nice 'CHUNK' sound, as I mentioned earlier I also assumed these were solenoids until I took one apart several years ago, but they are in fact motor based. The 200 and 700 series use the same actuator, at least up until the 1990 I have.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 10, 2023, 02:27:01 am
content: Nah, there's no such smart thing.The controller simply toggles the power for 1 second or so, if it doesn't detect the endstop, then it'll switch back, that's all it does.If something goes too wrong, like it did 9 years ago when the motor shorted out, it'll blow the fuse.The motor is square, 18x18mm. A little smaller than the original (24x18mm), but should be easy to fit with some spacers (Or hot glue)Those volvo actuators use much better motors, but this Mabuchis are absolute trash.I might buy few of these square ones for dissection!Then maybe fit one door with them and count the days it lasts without exploding or something.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 10, 2023, 11:04:17 pm
content: I ordered the small pcbs to jlcpcb, few DRV10974 and few motors:https://www.aliexpress.com/item/1005005356382793.htmlThey're a bit smaller, 16mm in diameter, should fit easily after pressing them into a small 3d-printed adapter.I also found this one, a bit expensive but provides all in one package:www.aliexpress.com/item/1005004210717603.htmlI didn't trust the 12V rating too much so I searched the embedded controller based on this picture:It turns out the APX9322A can work up to 17V (20v absolute limit).But the original shaft is 2mm, this one is 1.5mm..., too much mess so I'll wait for the first motor!

author: Psi
author_rank: Super Contributor
timestamp: June 12, 2023, 11:54:15 am
content: You sure you can modify the case to fit those round motors when it's designed for rectangular motors with rounded sides?

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 12, 2023, 08:37:51 pm
content: The motor is smaller than the original in all aspects, so yeah it will fit, filling the rest with a 3d-printed casing to make the rectangular shape like shown in the post before yours.

author: james_s
author_rank: Super Contributor
timestamp: June 12, 2023, 08:58:24 pm
content: Those motors look interesting, brushless with internal drivers? What are all the wires for?

author: Infraviolet
author_rank: Super Contributor
timestamp: June 12, 2023, 09:14:33 pm
content: Perhaps power, ground, and two for directions, with the two directional ones letting you do forwards, backwards, high impedance braking and shorted-terminals braking?

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 10, 2023, 02:59:31 pm
content: So two Aliexpress orders got lost, I made them again, and much, much later... here we go!Bought this BLDC:https://www.aliexpress.com/item/1005005356382793.htmlBut theDRV10974is programmed using tight tolerance resistors with rare values.Had fun for a few days with some multi-turn trimmers but never got the acceleration ok, it either desynced or ramped too slow.Given the car turns the locks for only 1 second, I visioned a total failure and ditched it.Then bought these motors, took like 1 month to arrive:https://www.aliexpress.com/item/32964868659.htmlCompared to the FC280, they run extremely smooth on 12V (Expected, having 6 poles instead of 3).I can barely hear them rotating nor the contactor noise, the FC280 sounds like a 80s diesel engine compared to them.The speed feels ok, spec says 7K rpm, feels close, plus the motor is fully sealed and won't get contaminated by any dust or whatever.Stall consumption is 1A, light load is 300mA and idles at 40mA.They use - quoted - "precious metal" instead carbon brushes, which I think it's better for this application, where the motor rotates for extremely short amount of time.I still think the major failure point of the original motors is exactly this, very short runs, no time to get rid of the carbon deposits that would normally get burn or vented away.I'll be making some 3d print spacers to hold it and hopefully get into it any of the following weekends.

author: Alti
author_rank: Frequent Contributor
timestamp: September 10, 2023, 06:49:35 pm
content: Quote from: DavidAlfa on June 07, 2023, 09:59:28 pmIsn't just periodic replacing of $4 motor at driver door a better approach? For sure you can extend its design lifespan from 5 years to 10 years, maybe 12 years, if you switch to BLDC. But, then you hit another item on a wear-out list in that lock. So, convert the lock to ease replacing the motor. Service it similar way as you replace air filter, periodically, lets say once in 3 years.

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 10, 2023, 07:39:52 pm
content: If you even read anything, I'm not going brushless in the end, but getting a different motor type.But it's up to me to decide how to invest my time, and I want to try improving that. So, where's the problem?I also do it for the friends I have in a private group, we all have the same car.The original locks are almost $200 each. Might last between 6 months and 5 years. It's a true lottery ticket.I'm replacing only the motors, but while one is already 5 years old and still strong, I've replaced another 4 motors.In total, it's been 7 motors in the last 8 years. And they newer break at the same time. So it's not all every 4 years. But a random one every 6 months or 1 year.I don't enjoy removing the door panels, power windows, getting messy, breaking some brittle aging plastic bits every time.Neither I will fell in the "get a new car" thing for some crappy locks!