Adding Alarm Chirp to Stock Alarm

[TalonSpeed]

I want to add a chirp to the stock keyless\alarm system. I noticed when I lock the car the foot lights flash twice and once for unlock. I figure the receiver located in the panel behind the driver seat sends a ground signal to either a relay or body control module and that triggers the lights to flash. If I tap into the wire for lock and unlock I can add a chirp.

Problem is I dont know which wires to tap into. According to the FSM the harness is E-42 and it has 20 pins!

 

[jjw205]

Subscribed. Glad I'm not the only one who has thought of this at one point. Just never found anything on it.

 

[luv2rallye]

The pin you want is pin 15 (blue-white wire to ETACS-ECU).

 

[TalonSpeed]

I am probably wrong, but why wouldn't it be pin 10 or 11? I cant tell which pins are ground. I haven't had to read a wiring diagram since college.

The ETACS ECU seems to only control the door locking, if I am looking at the diagrams correctly.

I want the chirp to chirp twice with foot lights for lock and once with lights for unlock. I also noticed if the doors are locked by remote then u try to lock them again, I hear the door lock actuator but the foot lights don't light up. Same for unlock. I guess this is set to let u know that U have already locked\unlocked the car.

If I wire them to the unlock\lock singal wouldn't I get the same one chirp?

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[luv2rallye]

I didn't know what your planning to connect. Sounds like you want to what, connect a speaker to one of these pins to get a chirp? Or connect a horn? What did you have in mind to produce the chirp? It makes all the difference. Unless it's the right voltage relay and possibly some extra circuitry, you won't have the power capability to drive anything that would produce a chirp. And even then it appears you may end up with it chirping whenever the locks are toggled - not just when the remote does it.

ETACS-ECU controls many things - not just door locks. And your E-42 pin 10 is a constant 12V while pin 11 is ground whenever the footlights are on (which is also while door is open, etc).

 

[TalonSpeed]

I want to use a piezo buzzer like most cars that have the chirp instead of horn honk. I got this one from RadioShack:

Model: 273-066 90DB Piezo Pulse

• 3-28VDC

• Maximum current: 12mA at 12V

• 2,800Hz

I want it to work like this:

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[TalonSpeed]

Another thought. Couldn't a diode keep the door opening from triggering the piezo buzzer if the diode was placed after the negative splice on the wire going to pin 11?

 

[luv2rallye]

Ok if it really does only draw 12mA max that's good. There's only a few places you can connect it however on this car's door lock setup. The problems as I see it will be the following:
1) It really is meant to operate at 12V or more - less and it won't be loud enough to hear outside.
2) If you put it on the door lock actuator (pin 6), that has a pullup resistor (in ETACS) to +5V which will probably prevent it from operating and may also interfere with the ETACS detection circuit on that actuator. And even if it works, it would chirp whenever the locks are toggled - not just when the remote does it.
3) If you put it on a door lock power relay (pin 12, 13, or 14) it may/may not chirp (or chirp all the time) but also may interfere with that relay operation since it's on the control side of the relay coil. And even if it works, it would chirp whenever the locks are toggled - not just when the remote does it.
4) That really only leaves pin 15 (as all other pins are used for power, ground, drive foot/dome lights, etc). The receiver doesn't state/show what pin 15 is/does but I suspect it gets pulled soft low when the remote button is pressed. However again ETACS has a pullup resistor to +5V which will probably prevent it from operating and may also interfere with the ETACS detection circuit on it. Also the receiver shows a series resistance on pin 15 (thus it's a soft low) which may prevent proper buzzer operation.

You might get it to work if you connect one side of the piezo buzzer to +12V (eg. pin 10) and the other side to pin 15. If the receiver's soft low series resistance isn't too much and can handle the additional current, it may just work.

 

[luv2rallye]

Another thought. Couldn't a diode keep the door opening from triggering the piezo buzzer if the diode was placed after the negative splice on the wire going to pin 11?

How exactly are you saying to connect the buzzer and diode since pin 11 is used to operate the foot and dome lights?

 

[TalonSpeed]

I assume Pin 11 is grounded when ever the receiver tells the foot lights to turn on. The wire going from pin 11 is connected to the pin 22 and pin 20 on the B-07 harness. I assume pin 20 is going to the door switch, which turns on the foot lights when the door opens. (Door opens and everything connected to Pin 20 including pins 11 and 22 are grounded) If you splice the negative side of the buzzer into the wire coming from pin 11 then put in a diode between the splice and pin 22 on the B-07 harness it should keep pin 11 from ever seeing ground with the door is open. The only time Pinn11 would see ground is when the receiver tells it to.

2 things:
I am not sure if a diode would work this way
I am not sure if the receiver needs to see that ground signal. (What if door is open and I press the lock\unlock button on the fob?)

Could I use pin 15 to trigger a relay that sends a ground to the buzzer?

 

[luv2rallye]

I assume Pin 11 is grounded when ever the receiver tells the foot lights to turn on. The wire going from pin 11 is connected to the pin 22 and pin 20 on the B-07 harness. I assume pin 20 is going to the door switch, which turns on the foot lights when the door opens. (Door opens and everything connected to Pin 20 including pins 11 and 22 are grounded) If you splice the negative side of the buzzer into the wire coming from pin 11 then put in a diode between the splice and pin 22 on the B-07 harness it should keep pin 11 from ever seeing ground with the door is open. The only time Pinn11 would see ground is when the receiver tells it to.

Hey I like it. Good thinking

2 things:
I am not sure if a diode would work this way

It should. Just keep the cathode end (striped end) towards the splice (NOT towards pin 22). And use a diode (rectifier) that can handle the dome and foot lights current - maybe 2 amps (NOT a signal diode). The 0.6V drop across the diode when you open the door will dim the lights slightly but will hardly be noticable.

I am not sure if the receiver needs to see that ground signal. (What if door is open and I press the lock\unlock button on the fob?)

The receiver does not need that ground. (I think everything should work like before because the receiver still knows the door is open via signal on receiver pin 2).

Could I use pin 15 to trigger a relay that sends a ground to the buzzer?

Maybe if the receiver internal resistance on pin 15 isn't too high preventing relay from activating. However I LIKE YOUR SOLUTION MUCH BETTER!
Let us know if it works.

 

[TalonSpeed]

I hope this diode works:
http://www.radioshack.com/6a-50v-rectifier-diodes-4-pack/2761661.html#pdpReviewsTab&tab=tab1

 

[luv2rallye]

It will. The stripe end is the cathode.
Connect the positive side of the piezo buzzer to pin 10 which is +12V hot all the time and already fused.

 

[TalonSpeed]

I will try this out this weekend.

 

[TalonSpeed]

Something doesnt work as we thought.

But I did get the system to work. I had to cut the Pin 2 wire. Pin 2 is used to tell the Receiver that a door has been opened. It does this via a ground wire attached to door sensor or foot lights. It is a solid ground (non dimming). Pin 2 also disables the fob if the door is open. The only negative to cutting Pin 2 is if you unlock the car using fob, the car will relock after about 25 seconds because the receiver thinks you didnt open a door. If you start the car, this kills the relock function and doors will remain unlocked.

Wiring is easy!

-splice positive lead of buzzer into Pin 10 for constant 12v (Red wire with blue stripe)
-cut wire going to pin 2 (Red wire with green stripe)
-cut wire going to pin 11 (Red wire with green stripe)
-Attach pin 11 wire (harness side) to negative on the buzzer
-Tee those two wires with a diode (striped end facing the Tee)
-attach the other end of the diode to the wire that you cut from Pin 11 that runs to the body of car

Key notes:
-the diode is used to block the dimming ground from the foot lights. If you dont block this the buzzer will sound when doors are open and will crackle ass the foot lights dim
-you have to cut pin 2 because it is attached to pin 11 inside the receiver. If you dont cut it the buzzer will sound when the doors are open and will stop as soon as the door is closed.
-the above picture of E-42 harness is a picture of the receiver side not the harness side. So the picture shows pin 10 as being in the top right corner, but looking into the harness it is the top left. If you get confused just look for the yellow wire (pin 7) and count across to get to pin 10

I suggest getting a pulse piezo buzzer (Model: 273-066 90DB Piezo Pulse) In the video I am sitting inside the car next to the buzzer. It pulses instead of making a constant noise. Unlocking the car, the buzzer will pulse for the same amount of time the foot lights stay on (about 2 secs), locking the car, the buzzer, pulses as the foot lights flash on and off two times.

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[luv2rallye]

The only negative to cutting Pin 2 is if you unlock the car using fob, the car will relock after about 25 seconds because the receiver thinks you didnt open a door. If you start the car, this kills the relock function and doors will remain unlocked.

- It's 30 seconds BTW (2g Tech Manual p. 4-18 and I just checked it).
- It's not starting the car that kills the relock function but rather putting the key into the ignition switch.
- This may be a slightly annoying negative for those who don't put the key in within 30 seconds. Examples: they are scraping the windows, or rearranging things in the car, or writing something down, or removing something from the car to give someone, or strapping in their kid, etc. However, offhand I don't see any way around it. And it may be worth the tradeoff for those who want the buzzer. Personally I'd rather have the headlights flash to not annoy those around me in a parking ramp.

 

[TalonSpeed]

Its not really that loud. When I get out the car I listen for the chirp to let me know the doors are locked. The chirp on my Mercedes is VERY VERY loud.