W124 Electrical Option Connector "X30"
 

Did you know that all W124 models have in the driver's footwell an electrical option connector? If you know all about it then you need to read no further. This connector is something every DIYer needs to know about because it makes DIY projects easier. This connector will be used in my next DIY project posted here so keep it in mind.

The electrical option connector, variously called a "coupler strip" (in EPC) or "X30" (in ETM) or "connector block" (in FSM) is a block of nine sets of five power terminals that are available for connecting accessories. The connections include switched and continuous power, illumination, and ground. Most cars will have at least some of the connections already in use -- in my '95 E300, five are in use leaving me with four for my projects. Connection to this block is as simple as plugging in a connector (part numbers later); the hard part is getting at the block if you've never done it before. Here's how.



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To get at connector X30, first move the driver’s seat back as far as it will go. Next, remove the carpeting until you’re down to bare floor. You now see the plastic kick panel that lines the left side of the driver’s footwell and forms the “dead pedal” on which you rest your left foot. This plastic panel is held by two fasteners and a hidden Phillips screw. You must pull off some of the door edging to get at the screw. The two plastic fasteners can be popped off with a couple of plastic pry tools. With the fasteners removed, the panel can be pulled down and away from the body of the car.



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Notice the hook on the back of the kick panel. You must pull the panel back until the hook comes out of its hole in the car body before you can remove the panel.



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The hook goes in the hole shown by the red arrow in this picture.



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A picture of the removed kick panel. It’s all one piece!



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Now you can see connector X30. The big cable running down and out of the picture to the right is for the emergency brake. It is stiff and a little in the way; releasing the brake allows the cable to flex and stay out of the way. The cover on X30 can be pulled off easily – no screws. Now you can see all of the connections.



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The nine rows are identical. Any option can plug into any one of the rows. The plug is called “Pin bushing housing (multiway connector),” part number 013 545 32 28 and the little metal pins (female) that go inside are called “round pin bushing (2.5 mm),” part number 002 545 99 26. Note that this plug is identical to the one that connects to the outside temperature display in your instrument cluster (except the early version with four pins). You may be able to get these connectors for cheap in a junkyard, otherwise PeachParts can get them for you.



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Here’s the diagram of the connector (from FSM, “Service manual / Chassis and Body / Series 124, Volume 1” section 54 [electrical system] page 152) with notes made by me. The “position 1”-type notes refer to the ignition switch; “position 1” is Accessory and “position 2” is “Run.” (You knew that, right?) Pin 1 is “hot” all the time. Be careful poking around it with metal tools; better yet, disconnect the battery or pull Fuse “C.”

There are other “consumers” using fuses “A,” “B,” and “C.” For accessories that draw large amounts of current you will want a separate battery connection with its own fuse. For example, in many/most W124s, Fuse “C” in some cars powers the alarm, the central locking system, the power antenna, the courtesy and trunk lamps, and possibly (depending on model-year) the radio/CD player. The “budget” for this fuse is thus 16 Amps less what the other accessories have already spoken for. Different models may have different accessories so check the card in your fuse box and see what accessories are already plugged into X30.

Pin 4 Illumination: Device “N40” refers to the transistor circuit that allows the rheostat in the instrument cluster to control more lamps without burning out. N40 is powered by Fuse 9, which is only 8 Amps. Don’t overload it.

Be conservative and think before increasing the size of one of these fuses. There may be a safer way. Check your fuse box listing for under-used or unused fuses and run a new wire rather than risk an overload.

Jeremy

That's a fantastic discovery, Jeremy! But also a lot of words :) It's a bus, right? Where you plug an accessory's connector along the bus is irrelevant?

You're planning connector X30b in the passenger footwell, right?

Sixto
87 300D

Bus Stop (Wet Day)
 

Getting on the bus early gets you a better seat, Sixto. :D

Jeremy

The only thing I remember from chemistry is the Pauli Exclusion Principle being called the bus seat rule.

Sixto
87 300D

This is really great information, thank you for posting it. Going into my MB bookmarks.

The FSM speaks of this connector when installing the outside temp gauge. I always assumed it was under the knee panel as the pictogram was quite bad.

Thanks

btw - the padding that I see hanging in one picture. Is this padding above the black plastic underpanel. I know the dash knee panel is padded on my car, but I dont have any padding above that black panel.

Padding
 

Yes, the padding is above the black plastic panel that lives in front of the lower dash ("knee") panel. It's hanging down because the plastic panel is attached at the moment by only one screw. AFAIK the padding is factory original. Many cars are missing this padding -- I assume it was thrown away during maintenance. It's in there loosely, I don't think it's attached at all except by friction and gravity.

Jeremy

I wonder if the W201 would have this also? As they were produced during the same time period....

Is the 5 pole buss block under the false pedal? Or up in the dash? I had the bolster out this week but did not see a block on my 93.

W126s have this plug bank too :)

Thank you very much for posting this information, it's VERY valuable!

Sorry for this dumb question but the picture shows few connectors that are straddling three pins. If one wants to use a switched HOT, which would be position 2, is it advisable to simply find a connector that straddles all three pins but only use the necessary wires for an aftermarket device?

Help?
 

I'm not quite sure of your (not dumb) question so let me answer several questions and maybe one will be yours.
(1) If you need a switched hot for your project, connect to pin 2.
(2) If you don't have one of the connectors, you can always use a connector that is already in place but isn't using pin 2. You'll need one of the little metal connector-pins.
(3) If you don't have any of the little connector-pins, you can always solder a wire to pin #2 in one of the connectors that's already there. Be careful not to cause a short-circuit.
(4) It's not a good idea to connect one wire to all three power pins (1, 2, and 5) because all three would then be hot all the time.

Does that help?

Jeremy

You answered my questions. I like the idea of having a connector similar to the ones already there, with three pins and just using one or two wires as necessary. So, HOT + GND or IGN + GND for a typical device. I figure you can find ground anywhere on the chassis but this is about as good as it gets!

Did you say you can get these 3 pin connectors on the back of the instrument cluster only?

Connectors
 

They are 5-pin connectors, which are used for X30 and also for the outside temperature display in the instrument cluster, under the speedometer. Identical part number and a lot easier to get from a car in the junkyard. If you have to buy a new one from Pelican Parts it doesn't matter which one you get, they are identical. Remember the plastic plug and the metal pins are separate items, part numbers listed in the OP. You don't have to buy all 5 pins, just as many as you need for the circuits you want to tap into. If you need only +12 Volts and Ground then you need only 2 pins.

Jeremy

Odd request...
 

Hi Jeremy,

Thank you for your excellent posting. This information has been invaluable.

Silly question though - do you have the part numbers of the connector base and cover ?

Why ?

My W124 has this connector but it only has 5 sockets rather than the 9 sockets on the one in your W124. Only one of these sockets is unused in mine.
It would be useful to have the additional four sockets for accessories.

I know i can cram other wires into the existing plugs, but would rather use seperate plugs.

I am fitting door-bottom courtesy lights (+12v "hot" supply) and would like to fit a 5V regulator for 'phone and GPS (+12v "switched" and GND).

Cheers,

Neil xx.