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Thread: Central Locking GM5 Module Repair Success Story.

  1. #1
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    Central Locking GM5 Module Repair Success Story.

    Hey guys/gals Im Whitey, Im new to the forum and just wanted to say hello to all and make my first post a good one.

    So as an old lurker and a new member, I decided to use my first post to share my success story with everyone tonight.

    Over the last year I have suffered intermittent issues with my door locks. Sometimes I could only unlock the drivers door, but not the passengers. When this would happen, the rear hatch wouldn't open, and the central locking button on the console would not operate. What was ironic, was that this would come and go, and sometimes would go weeks without fault.

    Yesterday it got to the point that the fob would not unlock any of the doors, it would lock them, but not unlock any of them. The central locking button was inoperative, and I had to get my kids in through the drivers door.

    I decided today to pull out the GM5 module, which was a trifle difficult but pleasantly easy compared to some of the things I have removed from this car. I took it apart and located the two double relays that are for the central locking. I realize that replacing the failed relays would be a pain in the booty considering that I had to put my soldering station in storage when we moved to our apartment. I also am a struggling college student and stay at home dad, so paying the 100 dollar bill plus postage to have repaired was out of the question.

    I decided to take my dremel tool and cut the top off of the relays (very very carefully).

    once opened, I used 320 grit sandpaper and sanded the contacts on both sides of both relays and then washed them out with alcohol. Sprayed in some electronics cleaner then used a blow dryer to evaporate any residue.

    I also used a small flat head screwdriver to readjust the contact points to a better tolerance to ensure that they made good contact when triggered.

    After that all that was left to do was to seal the relays back up with some plastic and tape and put it all back together.

    Greatly enough the central locking system is back to full swing. I can also tell that it is functioning better than before, because earlier, the locks seemed kind of sluggish when they would throw. Now they yank back pretty fast and hard when you lock and unlock them..

    My guesstimation is that over the years, spark gapping causes carbon buildup on the contacts and they gradually conduct less and less current until they completely fail...

    Now let me be the first to tell you that if you arent mechanically, or electrically inclined, this project should be left to the tech savvy, you can contact Scott, Ive heard he does awesome work. But , if you have the tools, and tackling something like this doesn't scare you, then it is quite rewarding to do something that saves you between 100 and 500 dollars or more.

    If you have any questions feel free.

  2. #2
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    Search bmwgm5.com

    The sandpaper trick is only a temporary solution. Suggest you replace the relays. Unless you have VERY GOOD component level replacement skills and VERY GOOD soldering equipment, send it in for repair.

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    Scary

  4. #4
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    The GM5 relay failure is quite common. Seems to show up between 8-10 years on many cars. Also seems to be more of a problem in the high heat, usually during the Summer when the car has been closed up in the sun.

    Also if you have auto locking enabled, you may experience the problem earlier as the door locks get much more of a work out, so the actual number of relay cycles will typically be higher than a car without the auto locking feature enabled.

    Also with auto locking enabled your problem is much more inconvenient. What happens is you may get locked in the car and have to crawl out the window! At least without the auto locking enabled you do not have to worry about getting out of the car when you get to your destination if you do not lock the doors while you are inside the car.

  5. #5
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    Quote Originally Posted by jfoj View Post
    Search bmwgm5.com

    The sandpaper trick is only a temporary solution. Suggest you replace the relays. Unless you have VERY GOOD component level replacement skills and VERY GOOD soldering equipment, send it in for repair.
    I agree totally, in many situations it would be best to send it for repair. I would also tell anyone who is not electronically inclined, or hasnt worked around relays very much to holler as Scott and have him fix you up, I hear he does great work.

    But in any case replacing the two relays is only a temporary solution in itself, because, since relays utilize a mechanical connection to conduct current, even they will fail again at some point.

    To be honest the only thing that can fail on a relay from nominal use is the contacts,,, aside from sticky hinge. And when I say nominal, I mean all voltages and currents kept within tolerance. Cleaning the contacts properly, and readjusting the gap between the contact points, and resealing them properly to prevent moisture from entering should (in theory), yield at least the same amount of use as I have previously gotten out of them. The failure is caused by tiny spark gap, everytime a contact point connects and disconnects on the higher current side, a tiny spark is created. This in turn carbonizes the outer layer of the contacts, which builds up over time until failure. This would be the same thing that happens to spark plugs, and on the points on older cars as well.

    I have a 1996 Mercedes c220 that I pulled the fuel pump relay, as well as the window relays out due to failure, and performed the same operation on. it has been 5 years since, and everything is still functioning perfectly fine.

    Also to note, a little (very very little)non-conductive lubricant such as high viscous lithium grease, on the hinge points also aids in a sticky relay, but it is best to use a hypo needle to place the lubricant so as not to get it in locations it is not meant to be.

    What I have found over my many years of working with electronics, is that relay maintenance can be beneficial, the one main issue, is that over time portions of the contacts will degrade. Meaning that as the spark gap slowly vaporizes microscopic portions of the metal, parts of the contacts will become flattened or pitted. This can be accounted for and corrected by putting pressure on both sides of the contacts and smoothing with a stiff abrasive to create a flush contact point, then bending and readjusting the gap between the points.

    Hope this helps.

    Quote Originally Posted by tool2510 View Post
    Scary
    It can seem daunting.

    But in all actuality I had the box out of the car in about 10 minutes.

    Removing the top of the relays (very carefully) took about 5 minutes.

    Cleaning and adjusting took about 5 minutes.

    fabricating new covers for the relays 20 minutes ( waited until sealant set)

    Placing back in the car took about another 10 minutes.

    All in all, less than an hour spent.

    All that I used was a
    Phillips head screwdriver (removed 6 screws holding glove box)
    10 millimeter socket w/ long extension. (remove one nut at bottom of bracket)
    dremel tool ( w/ small cutoff wheel to slowly groove the top of the plastic on relays)
    90% isopropyl alcohol
    residue free electronics parts spray
    320 grit wet/dry sandpaper (less chance of grits breaking free inside the relay as opposed to standard glueback paper)
    small flathead screwdriver for adjustments.

    to re-cover the tops of the relays I found a small plastic box from a dentist for kids to put their teeth in. the box pulls in half. I simply placed each half over the relays and siliconed around them. This holds them, keeps moisture and dust out, and also makes them easily removable should future maintenance need to be done.
    Last edited by whiteymack; 10-25-2012 at 03:36 PM. Reason: Automerged Doublepost

  6. #6
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    Relay contacts pit over time and if they are plated the surface gets degraded.

    Replacing the relays will net you another 8-10 years without having to perform relay maintenance.

    For the PITA removing the module is and playing with the relays, it is worth the money to have them replaced, while you can still get a direct replacement!

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    Mine occurred right after I got my car painted. That's what gets me to think that it can't be the GM5 module cuz it was working just fine before. My key pops the trunk open, gets the interior lights to turn on when unlocked but the doors will not lock/unlock and central lock button in the center console does not do anything either. So do you guys think, something is left unplugged when reassembling the car or it is the GM5 module? I need help It's really annoying.

    Sent from my iPhone using BF.com

  8. #8
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    Mine occurred right after I got my car painted. That's what gets me to think that it can't be the GM5 module cuz it was working just fine before. My key pops the trunk open, gets the interior lights to turn on when unlocked but the doors will not lock/unlock and central lock button in the center console does not do anything either. So do you guys think, something is left unplugged when reassembling the car or it is the GM5 module? I need help It's really annoying.

    Sent from my iPhone using BF.com

  9. #9
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    Mine occurred right after I got my car painted. That's what gets me to think that it can't be the GM5 module cuz it was working just fine before. My key pops the trunk open, gets the interior lights to turn on when unlocked but the doors will not lock/unlock and central lock button in the center console does not do anything either. So do you guys think, something is left unplugged when reassembling the car or it is the GM5 module? I need help It's really annoying.

    Sent from my iPhone using BF.com

  10. #10
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    Quote Originally Posted by jfoj View Post
    Relay contacts pit over time and if they are plated the surface gets degraded.

    Replacing the relays will net you another 8-10 years without having to perform relay maintenance.

    For the PITA removing the module is and playing with the relays, it is worth the money to have them replaced, while you can still get a direct replacement!
    Yes sir you are absolutely correct. That is exactly what I said in my previous post as well,l at the very bottom. The awesome thing is, that if you repair them and adjust them properly, they should last as long as the ones.. (Only recommend repairing once though, as more times could remove too much over time and they may fall out of tolerance and not make proper contact)

    Ive repaired high current starter relays in the same manner with a great level of success and longevity. As long as the pits dont form deep holes they can usually be sanded flush and the contacts readjusted to a tighter tolerance. The good thing about the gm5 relays are that they are in a relatively low current circuit meaning that the pitting from spark gapping will be minimal. Thus one good sanding/flattening and adjustment should keep them going for another decade provided that the cases are sealed back up very tightly.

    If these fail again within the next few years I will just build a multi-stage switching circuit to replace them with. That is what BMW should have done in the first place. Simply use a a few ic low current amplifier chips to drive some high current output transistors.

    The first stage drivers can be bought pre-packaged in IC`s and the transistors themselves would be best to use like a TO-5 case high current. With ic`s, transistors, a couple of caps, and a handful of resistors, plus a small breadboard, should be pretty cheap.

    Simply bias the output transistors below cuttoff so that they are not conducting, and use the input stage to drive them into saturation. thus allowing current to flow just as the relays would.

    In fact, I think I might break out multisim and draw up the design and shoot a printout to utiliboard and build one for fun.

    Then someone without high dollar desoldering kit could simply use wire cutters to carefully break apart the relays down to just the pins and then heat the pins and pull through, thus leaving the board and tracings intact. Then simply plug in and solder the daughterboard Ive made and voila permanent fix.

    Also, a couple of things on a side note, I modified a small 5 volt regulated power supply and mounted it behind the dash and ran two USB cable ends off of it to the center console. The power supply is capable of 2 amps at 5.2 volts with an input voltage of 9-14 volts. This allowed me to plug in my car dock for my phone, as well as have one more usb jack for whatnots.

    I also finally pulled out my business head unit, and patched into the cd changer to create an auxiliary input for my phone dock. I used a double pole double throw switch to route the audio. In other words with switch in position 1 you get changer audio, with switch in position 2 you get phone audio. This worked out great, because I wasnt willing to give up the ability to listen to cd`s from time to time.

    Something else Im thinking about after january, is I have a buddy wanting to trade me a high resolution touch screen, roughly the same exact size as a standard double-din head unit around 7 x4 inches. My thoughts are to replace the cd changer with a micro atx case and motherboard, and run linux on it. route that up to the touch screen (id have to relocate the AC control first). Use this for my audio/navi etc. The cool thing is that if I can decode the signals coming from the steering wheel buttons I should be able to write a little java code and create a winamp plugin or something that would recognize the steering wheel controls to control the music. I have a small (60 gig) SSD drive that I could use, This would prevent hard drive damage from the vibration from my subs (two 15 inch sundown nightshades).

    Granted this is all hinging on how much time my kiddos let me have lol...

    cheers.

  11. #11
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    You certainly sound like quite the electrician. The computer stuff I'm all familiar with but the other stuff...not so much. But I think that fix for the gm5 would be really useful for a lot of people on here.

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    Quote Originally Posted by smeli View Post
    You certainly sound like quite the electrician. The computer stuff I'm all familiar with but the other stuff...not so much. But I think that fix for the gm5 would be really useful for a lot of people on here.
    Ahh, Ive got a decent amount of experience in AC/DC principles, repairing and building stuff over the years (used to love to tackle repairing and modding things such as ham radio equipment and repairing car audio amps) ive also been in IT, professionally for about 18 years, (cisco, novell and microsoft certified), and decided in 2010 to go back to school for programming. I am loving Java right now, and am actually coding a couple of apps for android as we speak. One of them I think I may use as my final project this semester.

    As for the GM5 fix, I agree, totally removing the mechanical relays and replacing them with solid state hardware would give them an indefinite lifespan, as well as be pretty cost effective. Most of the newer cars have let relays go the way of the ghost, because of the inherent nature of the mechanical contact, moving into solid state drivers instead.

    Being as the transistors will always be at cutoff unless switched on, they should stay pretty cool and not need any hit-sinking, if one was to build a similar system for the windows, one would probably have to add a heat sink because of the amount of time the transistors would be conducting during the rolling up and down cycle.

    So what kind of computing things do you do? Im always interested in finding fellow computer brethren.

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    currently im in my last semester of college. my major is IT. ive done some consultation stuff for businesses and home users since i was 16. recently this summer i did an internship at time warner cable which focused on penetration testing of CMTSs and soho equipment. im taking a java class right now, but programming isnt my thing.

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    Yeah I feel ya there. Programming was never my thing either.. But after 18 years of networking, maintenance, repair, sales, corporate crap, etc. I finally had my fill. Decided that programming would be a more viable option for me.

    I do not want to move (too much family), and in order for me to continue to have a successful career in IT here where I live, I would have to, because IT has branched out and grown so much that there just arent any positions here in our little po-dunk area that could afford me like there was over the last decade. Granted in larger conglomerative areas this isnt such a problem.

    I found that through programming I could hit a niche here that hasnt become over saturated in my area yet. Plus it gives me an opportunity to do something that I could possibly do from home and be with my kids.

    Now it seems that programming is becoming my newest passion (something i never thought would happen). Now its in my blood, since ive been in electronics, and IT for so many years, as well as auto customization, and competition car audio,,, making things work has always been my MO, and programming is just another facet of that.

  15. #15
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    [QUOTE=jfoj;25316515]

    Also with auto locking enabled your problem is much more inconvenient. What happens is you may get locked in the car and have to crawl out the window!

    Can't you just pull the handle on the door twice, or will this not work because the module is broken?

  16. #16
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    [quote=epfenninger;25332825]
    Quote Originally Posted by jfoj View Post

    Also with auto locking enabled your problem is much more inconvenient. What happens is you may get locked in the car and have to crawl out the window!

    Can't you just pull the handle on the door twice, or will this not work because the module is broken?
    No, in some cases the passenger doors inside handles become disabled. I have personally had to have my children climb over the seats and come out of the drivers door due to this problem...

  17. #17
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    Whiteymack; Did you get anywhere with your Solid State GM5 Module? Mine has always played up with the boot release in the cold weather in the 10 years I have had the car! I have lived with it up until now as it only played up when the 3 degree warning came up, but its getting worse now. I dont think its the relays as everything works normally, except the boot release when its cold.
    Bobdisk, G0RJE

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    Replace the relaysRelatively easy to DIY if you're good at desoldering

    I also tried the 'sanding of the contacts' to get me by for several months... then I decided to just order the relays from Aliexpress (took a month to arrive but they cost me $2 each and free shipping to Canada).

    I just finished replacing the relays in my G5 and, like others have posted, the de-soldering of the relays is the trickiest part.
    Removal of the G5 module takes ~5 to 10 min if you're comfortable with a philips, a flat head, and vice grips.

    I didnt have a vacuum de-soldering iron so I used a 60 watt iron and a manual solder sucker (plastic suction plungerthing that you can buy at Princess Auto/Harbor Freight for like $5); you can also use solder wick if you have it. Please note that THIS IS THE HARDEST PART of the job.. and it really did 'suck'!

    It took me about 35 minutes to get all of the solder out and pull out the relays. Installation was super simple - and voila! It works like a charm!

    DSC_0008compressed.jpgDSC_0009compressed.jpgDSC_0010compressed.JPGDSC_0011compressed.jpg

  19. #19
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    Hmmmm, I thought that the relays are sealed. I know replacement relays are hard to come by from the usual sources such as Mouser and digikey. You can buy them on eBay.

  20. #20
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    Marco, you're correct - the relays are indeed sealed and to sand the contacts you'll need to carefully cut the tops off of them with a razor blade. However, sanding the contacts only bought me 2 or 3 months of life before they started acting up again. By that time i had already received my new relays in the mail. If youre good at soldering, and have a solder sucker, you can replace the relays yourself in under an hour.

  21. #21
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    Quote Originally Posted by jfoj View Post
    The GM5 relay failure is quite common. Seems to show up between 8-10 years on many cars. Also seems to be more of a problem in the high heat, usually during the Summer when the car has been closed up in the sun.

    Also if you have auto locking enabled, you may experience the problem earlier as the door locks get much more of a work out, so the actual number of relay cycles will typically be higher than a car without the auto locking feature enabled.

    Also with auto locking enabled your problem is much more inconvenient. What happens is you may get locked in the car and have to crawl out the window! At least without the auto locking enabled you do not have to worry about getting out of the car when you get to your destination if you do not lock the doors while you are inside the car.
    Just a note. I found that if I get all locks up, and disconnect the batter for a while when I reconnect that annoying auto-lock feature is disabled. Of course if you use the center switch or key fob to lock your doors the auto-lock feature is enabled again.

  22. #22
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    Wow, that's quite a first post! Glad you've had success; I've been repairing relays on my old BMWs in this manner for a good many years. And my wife's Sportwagon has started exhibiting exactly the same symptoms in hot weather (!) so I think I'll follow your lead and do a little GM5 rework...

  23. #23
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    Thumbs up Good Stuff

    Worked great. I wouldn't use a Dremel tool only because the plastic is quite soft, you can slice through it with a utility knife, quite thin. Boy, you really need to stay close to the lid so you don't hit all that flexible workings in there, quite a full relay box, and metal is close to sides. Looking at the two relays, with the plug connectors at the top, the top relay was my culprit for unlocking the passenger door and center console. Within that relay, both points are active when locking and the bottom one instrumental for unlocking. Initially I took notice that they are normally making contact with the outer top and bottom contacts, and triggering makes them contract towards the inner contacts. I pushed them closer at one point, did some electrical cleaning, then tried before final install and about jammed the passenger door so returned to normal gap, slightly less than an exacto razor thickness. Of course, I was only adjusting the inner tab, since the outer points are normally together anyways and I wouldn't want to mess with that more fragile metal tabs. Now I know what people are talking about with the door unable to open, even with manual inside latch, outside latch, and button appears halfway up and down...it will push down, then inside handle will raise but not fully, and door never unlock. Yikes! All electro-mechanical issue, but not with the door latch. So, I unhooked the battery and the door worked properly...back to the drawing board. I then used 600 grit automotive paper which was mild enough and thin enough to work with, folded once, scissor-cut to a 1/8" width. Presto, it worked. History: The center and passenger door were both fading and a new actuator in the center console worked for 6 months. The passenger unlock would work intermittently for the past 7 years of ownership but finally stopped altogether this year, minor click noise. I actually thought the driver door was about to start giving me trouble one hot afternoon. So, I replaced the passenger actuator/latch assembly and absolutely no improvement, $200 part last week. I had read about GM5 and sending it away, or buy new for 5-600 plus dealer has to program, but was hoping to avoid that. Finally, I ran across your post and another which referenced this one. I used some postal tape to keep the shaved covers back on...for future access.

    Now, if the internet could always be right for everything you read.

  24. #24
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    Quote Originally Posted by djbmw1 View Post
    Marco, you're correct - the relays are indeed sealed and to sand the contacts you'll need to carefully cut the tops off of them with a razor blade. However, sanding the contacts only bought me 2 or 3 months of life before they started acting up again.
    The cutting open and sanding of the relay contacts is only a temporary solution at best. You will need to go back and do it again and again over time. Replacement of the defective components should only cost $100 if you send it in.

  25. #25
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    Quote Originally Posted by scottjoh View Post
    The cutting open and sanding of the relay contacts is only a temporary solution at best. You will need to go back and do it again and again over time. Replacement of the defective components should only cost $100 if you send it in.
    My experience with fuel pump relays on early cars has been different - I use grits down to 1200 and then clean the reworked contacts with solvent, and I don't think I've ever had to rework one a second time or replace it. For me it's kind of a game - the goal is to not spend the money on a repair I can do myself. Nonetheless I concur that the ultimate repair would be to replace the relays with new ones. I've just not had to resort to that.

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