drothgeb

Hey guys, I wanted to have a methonal system primer button and I thought using the headlight sprayer button that I never use would be perfect so I thought I'd do a quick write up, you can use that button for something more useful

1. Disconnect the battery.
2. Pop the driver side fuse cover trim off. There is a small slot to fit a trim removal tool into (I inappropriately use a flat head).
3. Unscrew the fuse box via two T25 screws and pull it out of the way.
4. Reach in and disconnect the wire harness plug on the back of the light switch assembly. It is retained by a small arm that has to be rotated 90 degrees. Here is a pic of it removed to give you an idea of what you're reaching for in the dash. Push the small notch down and rotate towards the passenger side.
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5. Next remove the plug body from the wire connector by prying a small tab over a bump and sliding the connector out:
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6. Peel back the wire wrap a little bit to give you some room to work. The wires for the wiper button are pinned to spots 5 and 6. The wire colors are black with a blue line and brown with a blue line. Cut these two wires and crimp or solder what ever you would like to use the button for to the plug side of the wires. Make sure you tape up the two cut wires that are now dangling coming from the engine bay. Now I pulled the whole assembly out and went through every switch position of the light switch and sprayer button verifying what pins had or didn't have continuity to ensure those two pins are only used as normally open connections by the sprayer and are not used for anything else.
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7. Slide the plug back on, connect it back to the light switch assembly, put fuse block back in, put cover on, connect battery, and enjoy your new button function.
8. Also just to show with pictures there is a very open grommet just under the fuse box, if you disconnect the ECU(I always disconnect the battery before unplugging ECU plugs) and slide it out you can access the grommet from the engine side, then remove the three T25s holding the bottom plastic trim up in the driver footwell to pull the wires through. It's only insulated with some foam in a bag. Very easy.
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Any ways, enjoy and let me know if you have any questions.

Style_Front

We have a headlight sprayer button?

drothgeb

Well I don't, anymore.

cetialpha5

Depends what you have. I think they got rid of it in 2008-2009. The headlamp washers just come on when you have the headlights on and squirts after 5 presses of the washer fluid. Before that, you had a button if you had the headlamp washers. Those came with Bixenons, then later they came with the sports package on the regular E350's, not sure about the AMG.