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Old 09-18-2012, 02:26 AM   #12
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Join Date: Aug 2012
Location: Tucson
Posts: 138
My Ride: 2000 323i
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Today I installed my siren, valet switch, and tachometer sensing wire.

I use Directwire wiring diagrams to install my alarms. The e46 can be done commando, in the sense that you can test for all the wires that you need to tap into, but a wiring diagram makes it's a lot easier and faster. With newer cars having pretty much all of the functions controlled by canbus, mux, ibus, etc... a wiring diagram and databus module is virtually a must.

First I tapped into the tachometer wire at the diagnostic plug. It is the black wire (the only one). This is showing the diagnostic plug in the passenger side engine compartment. For vehicles that do not have this plug (01-05) the black tachometer wire can be found at the OBD data link connector under the driver side dash. According to Directwire it is pin #9

For this first connection I will go through it step by step to show how all connections throughout the install should be done.

The siren and tachometer wire are connected/mounted inside the engine compartment, and the alarm sits inside the vehicle. As such, we must find a way to route the wires from the engine compartment to the cabin. Most times you can find a factory spare rubber grommet somewhere along the firewall, or you can run your wires right along with the main factory boot. Other times you have to drill/make your own hole, make sure to install a grommet when you do. Lucky for us, the e46 has a couple of spare nipples in the main boot, and these are the ones we will be using for our install.

An interior view of the boot/nipples.

You can cut the tip of these nipples to run your wire. I on the other hand have a nifty little tool that allows me to run wire through rubber boots while keeping it intact.

Here is a view of the tool inserted into the boot/nipple from the engine bay compartment side.

Now lets make our tachometer connection. First we will strip the wire. Don't cut it, just strip away the insulation. You can do it will a razor blade, or with some side strippers like these.

Now stripped
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Last edited by benzovs; 09-18-2012 at 01:32 PM. Reason: updating info on tach wire
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