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mercedes benz vacuum pump problem

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=137550
Printed Date: March 29, 2024 at 4:43 AM


Topic: mercedes benz vacuum pump problem

Posted By: chassis
Subject: mercedes benz vacuum pump problem
Date Posted: October 27, 2014 at 11:52 PM

Good day. I have a question today about vacuum pumps. I'm helping a friend of mine with his mercedes benz W124. he has an alarm installed link to his central locking but it no longer works.

I've already read that there's 3wires from the main switch,1 is always 12v ,1 is always earthed and one changes pulse. i see at the pump at the back under the rear seat,they cut the control wire and connected their wires to it in order to operate with the alarm. I took the alarm wires of and reconnected the control wires as factory. the central locking now works ,it sucks and blows when switching the lock and unlock knob at driver door. I have notice when I arm the alarm,the alarm gives me beeps just after arming,indicates that one of the doors are open,that means the system won't lock or unlock.

I will sort that out tonight, but can someone please give me more clarity on what is happening when the driver switch gets push down and up. how does the switch send signals in order for the pump to suck and blow. and will the central locking still operate manually even though the alarm wires are connected to the control wire,one leg of the alarm to pump side and one leg of the alarm wire to the door side of the control wire. and I would also love to know where all the other wires from the pump are going.posted_image

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Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.



Replies:

Posted By: howie ll
Date Posted: October 28, 2014 at 4:08 AM
There are three control wires on that model a long time since I worked on one but two front door key switches are green and blue, trunk (boot) switch I believe yellow.
When a key is turned that wire changes polarity, it's either POS (+) at lock and NEG (-) at unlock or vice versa. Also needs a 3 second lock time to operate.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: chassis
Date Posted: October 28, 2014 at 4:17 AM
Thank you howie,Ill have a look again and test wires tonight.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.




Posted By: catback
Date Posted: October 28, 2014 at 9:36 AM
I'm lost, is something broken or is this a learning expedition?




Posted By: howie ll
Date Posted: October 28, 2014 at 11:58 AM
Don't ask me I'm just the teacher. BTW There's another way to do the locks,
Open the plate at the bottom, there are two wires going to the pump motor, you can do them as a 5 wire to control the locks.
I used to know everything about them but in a senior moment I forgot. Think there's an easy total close with them as well. What year?

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: chassis
Date Posted: October 28, 2014 at 2:22 PM
Hi its a 1997

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.




Posted By: howie ll
Date Posted: October 28, 2014 at 2:30 PM
There's a rubberised cable in the front floor loom each side, BROWN / black, RED / black and possibly blue/black, 15 seconds hold on the third closes windows and roof after lock.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: chassis
Date Posted: October 28, 2014 at 4:58 PM
I have found a burned tracks on the central locking module. the module that changes the pulse. exactly like the diagram on your site with the 2relays.I have problems uploading it now. what I have notice is,on the this car the doors lock with neg pulse and unlocks with positive pulse. When the driver door is open,the control wire has a +pulse. it cannot lock while open. So when I arm the alarm,a negative signal goes from left relay,the coil activates on the left and goes through the right relay to the vacuum pump motor,when the 3seconds is over the left relay goes back to 87a and touches the driver side wire which is 12V.so the control wire ends up 12v one side and negative one side. can this be the reason the 2 relays burned and the drivers door must be closed?

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.




Posted By: howie ll
Date Posted: October 28, 2014 at 5:23 PM
Firstly, why would you want to arm it with the door open?
In fact under normal circumstances arm the alarm with a door open, it simply won't lock.
Second they aren't pulses that flip flop from the locks, they are constant.
Very unlikely you damaged tracks, a fuse would have gone first.
Build quality on the SA models back in the 80s was awful but even the Euro builds suffered corrosion problems on that vacuum pump control board, even more so when trunk (boot) mounted, sometimes even when under the back seat and here we have a 17 year old car.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: chassis
Date Posted: October 28, 2014 at 5:48 PM
I assume that is what happened because the central locking did not work. so everytime a owner closes his driver side door improperly and arms his alarm he will fry his central locking module on this one wire vacuum pump system?

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.




Posted By: howie ll
Date Posted: October 28, 2014 at 6:02 PM
You're jumping to conclusions based on a lack of knowledge and you used that magical word "assume" when the correct word is know.
Know this. Your above scenario is incorrect because as I explained before, with either the key in the ignition or a door open, the lock controls simply won't work so no damage is done, key in or door open inhibits locking.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: catback
Date Posted: October 29, 2014 at 9:49 AM
Looking at the given diagram (link below) it is to be noted during a lock or unlock the switch and it's current power state is isolated from the signal being sent to the vacuum pump thus averting a potential short.

https://www.the12volt.com/doorlocks/page3.asp#vac




Posted By: chassis
Date Posted: October 29, 2014 at 10:08 AM
This installation was totally screwed. the door wire from the alarm wasn't linked to the alarm module. that's why alarm system thought the doors are closed and still send the signal to the relays while the driver door was accidently left open.

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Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.




Posted By: howie ll
Date Posted: October 29, 2014 at 10:15 AM
Fair enough.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: chassis
Date Posted: October 29, 2014 at 10:17 AM
Thanks and sorry howie.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.




Posted By: catback
Date Posted: October 29, 2014 at 10:24 AM
The alarm doesn't care if the doors are closed, it'll attempt to lock whenever told with the exception on the key being on.

If anyone knows of an alarm that won't respond to a lock command if a door is open or better yet waits till the door closes and then responds without a second lock command from the user I'd love to know the brand and model of alarm. I've yet to come across an alarm that behaved in that manner.




Posted By: chassis
Date Posted: October 29, 2014 at 10:27 AM
Autowatch 276rli,it doesn't send signal when a door is open,it gives me a few beebs indicating a open door

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.




Posted By: howie ll
Date Posted: October 29, 2014 at 10:29 AM
Local product, a bit over fussy but not too bad.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: chassis
Date Posted: October 29, 2014 at 1:50 PM
I have fixed the problem,I used the diagram with the two relays and I have sort out the doors.thanks Howie and team.I love this site.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.





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