Central Locking! - BMW Forum - BimmerWerkz.com
3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.

 
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#1 (permalink) Old 11-26-2005, 11:17 PM
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Central Locking!

Ever since I bought my 1991 BMW 318is E30 M42, I haven't been able to (at will) lock my doors. I was able to lock/unlock my trunk and passenger door manualy, but not the driver's side door.

Through this forum, and a few others I came across a few VERY helpful sites as to how the whole central/manual locking systems work. By reading these sites, I found that my lock cylinder needs to be replaced in order for me to manually lock the doors, but as for the central locking, it appeared that I had to dive much deeper.

I go to an automotive school and I just started the basic electricity course, but I have HORRIBLE teachers, and although I get straight A's in all the courses, I'm still very much so a novice with automotive electrical. So with all my peers and teachers present, I brought my car into the shop and removed my door panel on my driver's side and started tinkering.

My lock cylinder was completley F'd upon dissassembly. I kept the tumbler mechanism and moved on to the central locking problem. I d/c the battery and r/c the battery and start pushing the microswitch for the door. The door locks and unlocks 3-7 times every time I d/c and r/c the battery, then it stops working. If I wait for about 30 seconds, I can lock/unlock another 3-7 times and it'll stop working once again.

I remove the switch and test it with a DVOM. 0 ohms when the switch is pressed and infinate when it's closed. The meter also beeped with continuity... switch is good.

I remove the speaker panel in the driver's door to gain access to the central locking unit and the harness connecting to it. It's getting battery voltage. When I check the voltage at the switch's wires, I'm only getting ~9.4v. I follow the yellow with blue stripe wire to the CLCU and I find the voltage leaving the CLCU going to the switch is ~9.4v... looks like the unit is bad!

So, since I figured you can't break something that's broken, I pull out the CLCU and carefully remove the cover. It consists of 2 relays, a bunch of resistors, and what appears to be a voltage regulator... the circuit board isn't burnt, nothing is disconnected and everything appears to be completely normal. I clean the relay contacts which were moderately dirty and reassemble the unit. I connect it and check and it's still only giving ~9.4v to the switch.

I disconnect the CLCU and decide to jump the switch myself, so that it gets complete battery voltage. It locks/unlocks both doors, the trunk and the gas latch EVERY time...

I've been messing with this now for the whole Thanksgiving weekend, and it's driving me nuts... if there really is a voltage regulator on that CLCU, then the 9.4v it's sending the switch is prolly normal. The only other thing that may be screwed up is the electric motor in the door. It has brushes in it, and my thinking is that after 3-7 successful locks/unlocks, the brushes get too hot and don't allow the motor to work correctly. But then again, wouldn't the other laches in the car lock (assuming that the motors in those mechanisms are operating normally) even if the drivers door didn't?

One of my teachers said that my cylinder needs to be replaced, then it'll work properly. One of them said that the locking mechanism on the door is bad and needs to be replaced. Another one said the motor AND the CLCU are bad. I don't wanna shotgun-repair this thing and waste a bunch of money because I don't even have a job right now and I am COMPLETELY broke. I would be borrowing money from my parents to fix this problem. I have all the tools necessary at home to fix this. Please help me isolate this problem!!

Thank you =)
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#2 (permalink) Old 11-28-2005, 11:53 AM
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First up, WELCOME!!!!
Second, GREAT info!!!
Third, A long post like this will usually be ignored unfortunately. I have learned to break my posts down into bite sized chunks. Most everyone on the boards is reading from work, so time is limited. Make one an "FYI" type of post, then make a shorter one with JUST your questions. It will increase your chances of getting answers.
Fourth, I am having the same types of problems, but I haven't had the time to dig into it... no garage to work in during winter time, ARGH!!!

Again, Welcome!

Josh W.

Not currently on the Bimmer kick. Drivin' a 2003 Silver Civic at the moment, but I am STILL the Founding Member of the "325eXTATIC You're my hero" club.
Quote:
Originally Posted by <b>superdeadman</b><br>Josh W. IS my hero!

Originally Posted by <b>JoeMadoo</b><br>325eXTATIC, you're my hero...
Originally Posted by <b>Moosepuck</b><br>Oh yeah... 325eXTATIC...you're my hero...
Originally Posted by <b>e30dream</b><br>325eXTATIC....youre my hero.
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#3 (permalink) Old 11-28-2005, 04:35 PM
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Update...

At school today, I found out there's a TSB (Technical Service Bulletin) on the central locking in my car. It appears that the CLCU goes bad because one of the components inside breaks. It is non-serviceable, and needs replacement. I will order the new CLCU hopefully today, and will re-post my results.
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#4 (permalink) Old 11-30-2005, 12:50 AM
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Update...

I got the new lock/CLCU today, and, sadly the problem still exists. Although now I'm getting 10v to the switch instead of 9.4v, and I can get it to work about 10-20 times before it stops.

The new lock works great though. I took it to a locksmith and he re-tumbled it to my old key for 20$, so now I can at least lock all my doors manually.

I unplugged the switch and tested the terminal it plugs into and I'm getting 10v. I unplugged the motor and the switch and checked both of their terminals and I'm getting 10v. The CLCU is new, not used so I'm pretty sure it's ok. I checked fuse 27 and im getting battery voltage out of it, all the way to the CLCU. So, now, the only thing left is a bad ground I guess... but the brown (ground) wire goes way down into ... well, somewhere that I can't even see so that means more frustration and another post soon =)
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#5 (permalink) Old 11-30-2005, 12:48 PM
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Turning into an awesome FYI post man! Keep up the good work! Oh, and STAY IN SCHOOL! LOL

Josh W.

Not currently on the Bimmer kick. Drivin' a 2003 Silver Civic at the moment, but I am STILL the Founding Member of the "325eXTATIC You're my hero" club.
Quote:
Originally Posted by <b>superdeadman</b><br>Josh W. IS my hero!

Originally Posted by <b>JoeMadoo</b><br>325eXTATIC, you're my hero...
Originally Posted by <b>Moosepuck</b><br>Oh yeah... 325eXTATIC...you're my hero...
Originally Posted by <b>e30dream</b><br>325eXTATIC....youre my hero.
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#6 (permalink) Old 11-30-2005, 10:40 PM
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Update...

I found the ground by using the programs I have at school, but it took FOREVER! By removing the panels under the driver's side dash area (under steering wheel, and above pedals) and a trusty flashlight, I found the common ground. It's mounted above the brake pedal assembly but toward the driver's seat a little bit. It's a bolt that has about 4 grounds on it. I found that everything in the driver's door is grounded to this spot. After inspecting it it looked normal. I cleaned it and all the ground wires connecting to it and I got good voltage reading (0.0 volts). Reconnected everything and I still got the 10v's going into everything in my door.

So, I guess that's it! Everything in the door must be meant to run off of 10v. Imagine, if you will that everything runs off of battery voltage. With a 2-2.5v decrease, most of everything wouldn't work at all. The motor especially wouldn't be able to operate off of 10v, AT ALL, not just intermittently. I can roll down both windows at the same time with no problems, and both the side mirrors work perfectly.

So, why the central locking cuts out after 20 tries? That's the puzzler, but it's most likely because the electric motor's brushes get too hot to operate, which is why I can wait a few seconds and they'll lock/unlock a couple more times before it stops again. I could clean it out, but why bother? It's not like I need to lock/unlock my doors 20 times in a row on a regular basis anyway. For the past few days I've been just using the car normally, locking it every time I park and unlocking it every time I need to get in. I've had zero issues with it not locking or unlocking when I need it to.

As you can tell, most of this is speculation. I'm going to bring my car to school tomorrow and check everything over ONE LAST TIME. I'm going to ask every available instructor what he/she thinks about it and if I can't get 12v to that door, then it may be alright.
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#7 (permalink) Old 12-01-2005, 12:10 PM
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I honestly have never played with my locks that many times in a row, but with windows on newer cars at least, they have an "anti-stupid kid function" as I call it... That simply stops them from being able to move for a few minutes if they have been playing with the switch excessively. Have you let the system "chill out" for 10 minutes and tried again? Any clue if that is a function of the CLCU? I doubt it is, but hey, it's the only idea I can think of!

Thanks for all the info!

Josh W.

Not currently on the Bimmer kick. Drivin' a 2003 Silver Civic at the moment, but I am STILL the Founding Member of the "325eXTATIC You're my hero" club.
Quote:
Originally Posted by <b>superdeadman</b><br>Josh W. IS my hero!

Originally Posted by <b>JoeMadoo</b><br>325eXTATIC, you're my hero...
Originally Posted by <b>Moosepuck</b><br>Oh yeah... 325eXTATIC...you're my hero...
Originally Posted by <b>e30dream</b><br>325eXTATIC....youre my hero.
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#8 (permalink) Old 12-04-2005, 10:05 AM
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Central Locking

I have posted before, but, I had similar issues with my 1990 325ic( could not unlock passenger door by any means, could unlock trunk, could not lock drivers door with key) I replaced from salvage the central lock control and the drivers door lock motor and now everything works except I cannot lock drivers door from drivers door key lock. I am in process of buying arekey lock cylinder and installing, but before I do that I need to see if the arm on the lock cylinder is actually going in the slot on door lock that controls lock/unlock function (just maybe the arm is atopc the slot and will unlock but not lock the door.
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#9 (permalink) Old 12-06-2005, 11:46 PM
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I brought the car in one last time, and I decided I'd get to the bottom of it, if it killed me...

.. I went to the BMW step program at my school!

Normally, new aspiring techs like myself aren't allowed to talk to these people, or go into their shop.. but I figured I'm paying so much to go to this school, they can go fuck themselves if they have a problem with me asking some questions!

I spoke with an instructor in the BMW step program for a good hour and a half about this. We pulled up schematics, looked on their software, and of course I checked out a bunch of the cars they have in there =) They have a mock up M10 with the instrument cluster mounted on the side of it, and all these kids are troubleshooting it, calling it an M20.. I just couldn't resist poking in and correcting them! But I'm getting off-topic here...

The instructor was stumped on the 10v's coming out of the CLCU. We just could NOT get an answer for it anywhere we looked. When I explained to him that it cuts out after 20 tries or so, he said that it's most likely the motor getting hot, and to just try out the locks normally for the next few weeks and see how they work. So far everything has been OK. If I have any more problems I can go back to him (at least that's what he told me).

I think it's fixed! I've been driving the car to/from school 5 days a week and the locking system has not failed me yet! Still crossing my fingers, but if anyone has questions about this system I'll try my best to help ya'll =) Sorry there was no climactic, "THIS IS THE ANSWER!" to this topic, but, as long as it works, I'm happy!

Last edited by and0pand0; 12-06-2005 at 11:53 PM.
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