Mercedes-Benz Forum banner

1 - 20 of 51 Posts

·
Registered
Joined
·
182 Posts
Discussion Starter #1 (Edited)
Okay, I saw discussion somewhere here from like a decade ago and I think it died off, I'm getting no replies. This is very long winded, so I apologize but I'm so frustrated that this should be so damn hard!

1995 W124 WAGON with a brand new Audiovox AA25 keyless entry. I also have a good known working keyless entry (from United Auto Security) for my other W124 sedan that works just fine.
Note that on this wagon the door locks work perfectly up and down with the key in either the drivers door or passenger door.

Before I start, here is how I hooked it up to my other W124 sedan that works just fine. It is just a 3 wire deal. That's it. Blue, Green, Yellow (Driver door, passenger door, trunk). The three colors come in from the loom and right to the round connector at the vacuum pump. I cut the blue wire, put the input and output wires from the keyless on each end of the cut blue wire, and it works in the sedan just fine. Of course you put its 12v to the red wire on the square connector going to the pump, and its black wire to the brown ground wire on the square connector on the pump, etc.

So ONTO THE WAGON:
I put the 12v power wire from the Audiovox (or United Auto Security) to the red/white wire on the square plug of the vacuum pump like usual
I put the black ground wire from the Audiovox (or United Auto Security) to the brown wire on the square plug of the vacuum pump like usual
When I hit the remote, the module (both Audiovox and the United Auto Security one when I tried it seperately) clicks just fine, so I know both are getting power.

Well, the Wagon doesn't have just 3 in from the loom going from front of the car to the round connector at the vacuum pump. It has six. Ya. It has 3 blue, 3 green, and 3 yellow. Also, it has a split 't' from that same loom that doesn't have 2 of each color, but just one of each color and it goes to a connector that is white on one end and black on the other. It then does a u-turn and goes into a second loom back towards the front of the car.

If I do the same method on one blue wire going to the vacuum pump round connector, the remote won't do anything. Again, remind you that it does click so its getting power. One thing to note is that when the keyless is tied in between the two cut ends of the blue wire, even though the remote doesn't do anything, the key in the door still will run the pump. If I leave those cut blue wire ends exposed, the key won't even work. So at least I know that the keyless module is completing the loop of the two broken ends of the blue wire.

Neither keyless module (audiovox or United Auto Security) works, yet they both work in my sedan W124.

Can anybody let me know what the hell I'm supposed to do with this wiring? I did try making the 2 blues that come out of the round connector tie together, and every other blue coming from the loom(s) sides together with the keyless going to each of those sides of the equation, but still nothing.

I saw other forums with people talking about a yellow wire, but I've done this exact scenario in this writeup on the green and yellow wires as well. As you can see I have quite some TIME into this and I'm beyond frustrated. Can someone please advise before I jump to the moon? Pics attached of my current factory setups.

Thank you!
 

Attachments

·
Registered
Joined
·
182 Posts
Discussion Starter #3
Thing is i dont have that brand of module in the example. ...calls out wire colors exclusive to that module...?
 

·
Moderately subtle
Joined
·
11,988 Posts
That's fine, while the wire colors may be different, they all work essentially the same way. What I wanted to point out was where they said only one of the two green wires in the round connector is correct, and you can get the wrong one.
And the more I google, the more I see reference to that pulse length. Yeah, some cars will take the shorter pulse, but the recommendation is to always use the longer pulse of 3 seconds. I highly recommend changing that.

Now, I've also found some wiring diagrams for the locking system itself, but I don't want to give you information you already have. I also don't know your background and don't want to tell you stuff you already know or that you don't want to. I'm an old fart retired electrical engineer, and I've actually installed 6 of these, 3 in W124's and 3 in other old MB's, so I can probably talk you through this once you've decided the moon thing ain't happening.
 

·
Registered
Joined
·
182 Posts
Discussion Starter #5
Pulse length already set as one of the units I tried was from my sedan and it works fine.

I tried the green wire already as well...both actually.

I'd appreciate more help. If it was only 3 wires going in I'd be done. Its that 2 of everything and the loop back connector that makes it different.
 

·
Moderately subtle
Joined
·
11,988 Posts
Ok, so you're saying the pulse length is set to 3 seconds? One of the modules I have is a UAS, and I can tell you it has 2 pulse lengths user selectable. Your sedan may be one of the cars that the shorter pulse length is adequate. No matter what, don't assume that the fact the pulse length works in the sedan is proof that it is OK in the wagon. One thing about the UAS module, the pulse length on mine is adjustable with little jumpers rather than the hokey way that audiovox module works, hope yours is the same so you can at least try out a longer pulse length:
https://www.benzworld.org/threads/wire-color-for-remote-door.2233889/page-2#post11347938 Post #29

Either way, according to the instructions for the module you have, you get a pulse of +12V from green to red (green being positive) for "lock" and a pulse of -12V from green to red for "unlock." Were it me, I'd hook up a meter to those two leads with the module installed in the sedan (and working) and verify that is true.
 

·
Registered
Joined
·
182 Posts
Discussion Starter #7
Interesting, I'll have to look at this this weekend. Thanks for the inputs, I'll be back.
 

·
Registered
Joined
·
1,027 Posts
Did you get this sorted? I seem to remember one keyless install I did not working when splicing into the green wire near the plug but it worked after moving it by the "t-split".
 

·
Registered
Joined
·
182 Posts
Discussion Starter #9
Well, I'll put it this way. The United Auto Security instructions say to place the jumpers for a single pulse 3.5 second time. I moved the jumpers to that. Unit clicks, no door locks.
Again, I'm putting the white wire on the pump side of the cut wire, and the white with black stripe on the other side of the cut wire away from the pump. Also their instructions said that with the doors unlocked the "green" wire should have 12 volts. And with the doors locked, zero volts. So I tested that with a meter. When used the key to lock and unlock the door, yup, the green wire behaved exactly as such with 12v at unlock, and zero v at lock.

Since I'm NEVER one to mutilate my car, this had me pissed off so I tried every....single.....wire.
I know I can just solder them back and put heat shrink tubing around each one individually to make it permanent again.

I tried the yellow wire at the Y split, blue wire at the Y split, green wire at the Y split. I tried the yellow wire at the pump plug, blue wire at the pump plug, green wire at the pump plug.

I tried all the greens tied together from the frame side with the white/black wire from the keyless, and all the greens tied together on the plug side with the white wire.. Did that with the yellow and blues too. Nothing.

At this point I have no clue. This shouldn't be this hard.
 

·
Moderately subtle
Joined
·
11,988 Posts
Well, I'll put it this way. The United Auto Security instructions say to place the jumpers for a single pulse 3.5 second time. I moved the jumpers to that. Unit clicks, no door locks.
Again, I'm putting the white wire on the pump side of the cut wire, and the white with black stripe on the other side of the cut wire away from the pump. Also their instructions said that with the doors unlocked the "green" wire should have 12 volts. And with the doors locked, zero volts. So I tested that with a meter. When used the key to lock and unlock the door, yup, the green wire behaved exactly as such with 12v at unlock, and zero v at lock.

Since I'm NEVER one to mutilate my car, this had me pissed off so I tried every....single.....wire.
I know I can just solder them back and put heat shrink tubing around each one individually to make it permanent again.

I tried the yellow wire at the Y split, blue wire at the Y split, green wire at the Y split. I tried the yellow wire at the pump plug, blue wire at the pump plug, green wire at the pump plug.

I tried all the greens tied together from the frame side with the white/black wire from the keyless, and all the greens tied together on the plug side with the white wire.. Did that with the yellow and blues too. Nothing.

At this point I have no clue. This shouldn't be this hard.
Now that the UAS is/was set to 3.5 seconds, can you hook it back in and watch your meter while you press the buttons on the fob to see if the voltage behaves as it should? Measure voltage on the wire going to the pump.
 

·
Registered
Joined
·
182 Posts
Discussion Starter #13 (Edited)
Now that the UAS is/was set to 3.5 seconds, can you hook it back in and watch your meter while you press the buttons on the fob to see if the voltage behaves as it should? Measure voltage on the wire going to the pump.
Okay, so picking the green wire as the one to go with...by that I mean the cut green wire coming from the frame (or from the direction of the door locks towards the front of the car) and connected the white wire with black stripe from the remote unit to it. The other side of the cut green wire that comes off of the vacuum pump's round connector I have hooked the white wire without black stripe.
On the white wire going to the cut green wire on the round connector I put a voltmeter. When the doors are unlocked and open (since I used the key in the lock to unlock the car) and I just sit there with the probe on that white wire/green wire combination going to that round connector, it reads 11.8 and it will hold that forever. So I figure at least the remote unit is passing the power through. When I hit the remote's 'lock' button, the voltage on the meter reads about 3 or 4 volts for 2 seconds or so, and then raises back up to 11.8 again.

For grins I switched the white wire and the white wire black stripe's positions, and same sort of result.

Also for grins, I took the OTHER united auto security unit from my other w124 that works, and it gets the same readings...11.8v unlocked, and hitting the 'lock' button on the remote makes it read 3 or 4v. Then hitting unlock button again on remote makes it go back to 11.8.

For super grins, I took that OTHER united auto security unit immediately back to the W124 it came from and readings are different. Meaning, using the same test, when I put a meter on that car on the vacuum pump side, it reads 11.7 unlocked, and when i hit lock on the remote it goes down to ZERO...and holds zero forever. Hit unlock, and back to 11.8 again.

So what's the difference?
What is next? lol
 

·
Moderately subtle
Joined
·
11,988 Posts
Okay, so picking the green wire as the one to go with...by that I mean the cut green wire coming from the frame (or from the direction of the door locks towards the front of the car) and connected the white wire with black stripe from the remote unit to it. The other side of the cut green wire that comes off of the vacuum pump's round connector I have hooked the white wire without black stripe.
On the white wire going to the cut green wire on the round connector I put a voltmeter. When the doors are unlocked and open (since I used the key in the lock to unlock the car) and I just sit there with the probe on that white wire/green wire combination going to that round connector, it reads 11.8 and it will hold that forever. So I figure at least the remote unit is passing the power through. When I hit the remote's 'lock' button, the voltage on the meter reads about 3 or 4 volts for 2 seconds or so, and then raises back up to 11.8 again.

For grins I switched the white wire and the white wire black stripe's positions, and same sort of result.

Also for grins, I took the OTHER united auto security unit from my other w124 that works, and it gets the same readings...11.8v unlocked, and hitting the 'lock' button on the remote makes it read 3 or 4v. Then hitting unlock button again on remote makes it go back to 11.8.

For super grins, I took that OTHER united auto security unit immediately back to the W124 it came from and readings are different. Meaning, using the same test, when I put a meter on that car on the vacuum pump side, it reads 11.7 unlocked, and when i hit lock on the remote it goes down to ZERO...and holds zero forever. Hit unlock, and back to 11.8 again.

So what's the difference?
What is next? lol
It is supposed to take the wire towards the round connector to ground for "lock" operations and apply 12V to that wire for "unlock" operations. It provides continuity between the two ends of the cut wire when sitting idle.
This is the AA925, right? I'm looking for a schematic for the unit to see how or if the ground is connected internally to the relay contacts. For now, you sure you've got a good ground? With 3V sitting on it when it is supposed to be receiving a ground, ain't gonna work. Is it the black wire that supposed to be chassis ground?
 

·
Registered
Joined
·
182 Posts
Discussion Starter #16
Actually I have the power and ground directly from a car battery sitting next to the car going to the united Auto Security Unit. The reason for this is that I have the Audiovox unit hooked up to the power and ground at the square plug at the vacuum pump. The Audiovox is the unit I want to be in there, and the United Auto security Unit only comes into the picture with its own battery source because I know it works in the other cars. I didn't want to have to undo the Audiovox ground and power to the square connector because the way they are spliced in is with those "shut the jaws on the wire" type of splicing connector and I didn't want to have to undo those clips on those connectors and go back and forth on the same wire using that method with two different keyless units. I hope that makes sense.
 

·
Registered
Joined
·
1,027 Posts
Okay, so picking the green wire as the one to go with...by that I mean the cut green wire coming from the frame (or from the direction of the door locks towards the front of the car) and connected the white wire with black stripe from the remote unit to it. The other side of the cut green wire that comes off of the vacuum pump's round connector I have hooked the white wire without black stripe.
Correct me if wrong, but sounds like you're connecting the leads from the keyless unit at two different points?
 

·
Registered
Joined
·
182 Posts
Discussion Starter #18
Correct me if wrong, but sounds like you're connecting the leads from the keyless unit at two different points?
Yes, two different points per the instructions. You cut the input wire (green, blue, yellow, who knows at this point) and on the vacuum pump end of that wire you put the keyless wire. On the other cut end of the wire going back into the car's wire loom you put the other keyless wire.
 

·
Registered
Joined
·
1,027 Posts
Previous post sounds like you connected one lead near the plug on the vacuum pump and the other further down the harness.

Anyway, my suggestion is to splice into the green wire at one of these two points. Has worked for me installing keyless on S124.
 

Attachments

·
Moderately subtle
Joined
·
11,988 Posts
Actually I have the power and ground directly from a car battery sitting next to the car going to the united Auto Security Unit. The reason for this is that I have the Audiovox unit hooked up to the power and ground at the square plug at the vacuum pump. The Audiovox is the unit I want to be in there, and the United Auto security Unit only comes into the picture with its own battery source because I know it works in the other cars. I didn't want to have to undo the Audiovox ground and power to the square connector because the way they are spliced in is with those "shut the jaws on the wire" type of splicing connector and I didn't want to have to undo those clips on those connectors and go back and forth on the same wire using that method with two different keyless units. I hope that makes sense.
Ok, I get that and don't blame you, but remember the vacuum pump is grounded to the chassis of the car that it sits in, and you have to apply a ground from that same car to the wire in the round plug. If you're hooked to a separate battery with these "extra" units you're swapping in, you have to be sure to ground the negative of that battery to your car.

After that, make sure that black wire connected into the square plug reads continuity to ground with your meter. Read it in the plug that connects to your AA925 unit.
 
1 - 20 of 51 Posts
About this Discussion
50 Replies
5 Participants
nehuge
Mercedes-Benz Forum
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!
Full Forum Listing
Top