W126 keyless entry installation - Page 3 - PeachParts Mercedes-Benz Forum

carman850 · #31 04-08-2002, 07:57 PM

I installed JCwhitney Valiant remote controller on my W124( 92 400E) 2 months ago, it's running perfectly, I got the idea from mbcoupe.com:

http://www.mbcoupes.com/audioalarm/alarm/keylessentry1.htm

But I got the cheaper version of Valiant, it has only 2 buttons(lock and unlock), the original valiant system described in mbcoupe.com had 3 buttons, the 3rd button was wasted(for trunk release).

Because my 2 button Valiant has different PCB layout, I did figure out the proper connection by a multimeter and cut some tracks on the PCB, also soldered some wires on the PCB, then I also mounted the receiver on the back of tail light.

By using exact the same remote controller as described in mbcoupe.com, you just need to completely follow the instruction. For W126 and W124, the color code for the wires may be different, the control line is yellow, the +12V may be Red or Red/White, the Ground may be Black or Brown. It's good to verify it with a multimeter first.

jsmith · #32 04-08-2002, 09:24 PM

carman850,

i think that's the same one i have - haven't gotten it yet. can you explain the need to rewire the unit? i thought i had it figured out from:

this explanation

it appears that all you need is for it to send a + or - 12v to the vacuum pump and it says there are built i relays. i had decided that wiring at the pump itself was more straightforward...

carman850 · #33 04-08-2002, 10:30 PM

Joe,

Mercedes uses unusual center door lock, there is only one wire in each front door and trunk which controls the center door lock, when this wire has 0 voltage (Grounded), it unlocks all doors, when it has 12V voltage, it locks all doors. when it doesn't operate, it stays with high impedance. Please note, it doesn't require a constant voltage, all it needs is a longer than 2 second pulse to allow center air pump under the rear seat to finish the operation.

So the object of the add on remote control, is to ground that wire for about 2 seconds when "unlock" key is pressed, and to connect the wire to 12V voltage for 2 seconds when "lock" key is pressed. After that it should maintain the original connection, one may still be able to use key to open all door.

If you ordered the 3 button Valiant remote control, it has 3 relays, one closes for about 2 seconds when "unlock" button is pressed, and one closes for about 2 seonds when "lock" button is pressed, the 3rd one is for remote trunk release which you don't need. You can not just simply use one relay to ground it, and use the other one to connect it to +12V, because if you accidentally press one button right after you press the other one, you will have a short circuit.

Because Mercedes is unique, you need to modify the PCB board for the target above. I have attached the schematic from mbcoupe.com, the author was very smart to put two relays in serial, it doesn't interfere the existing mechanism at all, and there is no risk of short circuit.

It'll also be good if you install it near the air pump, only the control range may be less due the shielding caused by metal body and tint glass.

jsmith · #34 04-09-2002, 05:55 AM

thanks, that finally makes sense. i think i only ordered the two button remote. i guess i'll have to take a hard look at that pcb and see if i can figure out how to do the same modifications.

and yes, the main reason i would put it in the trunk is to get the extra range...

jsmith · #35 04-15-2002, 06:31 PM

carman850,

from the schematic and from checking the relay functions, i determined that the momentary contact poles are shown in this picture. i figured that the connection between those two are what need to be snipped. it appears that the etchings are on the other side of the board. now did you have to desolder and remove the relay to get at the connection between the two pins?
help! i didn't count on having to do that - i just might send the thing back!

thanks

carman850 · #36 04-15-2002, 07:09 PM

Joe,

It's too bad, the track connects those two pads is on the component side of the PCB, it's under the big black relays, you have to use desoldering gun or vacuum gun with a solder station to remove the relays in order to access that track.

jsmith · #37 04-15-2002, 08:20 PM

Rats! Anyway, thanks for the confirmation - I might still give it a go. If they had only not connected those two, this little unit could really be a Universal keyless remote. I figure you only need to solder one of those pins to ground and then use the other connectors.

carman850 · #38 04-16-2002, 09:17 PM

My two button Valiant has only one remote, it doesn't look as nice as those OEM ones, more like a cheap toy for kids.

jsmith · #39 04-17-2002, 03:20 PM

it's not really that cheap looking

, my $300 Viper remote start in the family van only has a few extra buttons but otherwise does not look that much better. all in all this is an excellent value at $40 shipped.

for those interested in doing this - i did have to desolder one of the relays and snip the connection between the two contacts i mentioned previously. not a big deal, you can get a $3 desoldering bulb at RS. then i had to jumper the lock relay contact to +12v. the other contact still had a wire that i simply spliced into the black (ground) connection. the rest i accomplished by splicing the wires together (relay series connection). i stuck the finished unit in the cranny above the right tail light with velcro and snaked the wires down underneath where i spliced into the trunk lock actuator harness. it passes directly underneath which is very convenient. the harness is sheathed in black and you have to cut through to get to the yellow, red and brown wires. i drilled a hole in the tail light assembly and stuck the antenna thru there and secured it with a small piece of duct tape. the range is pretty decent and it works as advertised including arming the factory alarm.

if you're not interested in features like flashing confirmation lights & beep etc, this is the easiest way to go. if you need other features you will have to wire into the convenience module underneath the rear seat.

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