DEI 508D Motion Sensor, Trigger Warning Chirp Without 2-Way Alert

I installed a Viper 350 Responder (3305V) 2-way car alarm system in my 2000 Subaru Legacy last month. It works great. However, the thieves in my area are particularly stupid. One bashed out my passenger side window last week, then ran away after the shock sensor triggered a Warn Away chirp. I have the Viper stickers on each side of my windows and the blinking blue light on the top and center of my dash. Not sure what he was thinking, maybe that it was a decoy light? Guess he didn't notice my dash cam either, because I caught him on video and got his license plate. =D Nothing was stolen, and the 2-way key fob woke me up immediately. So I was out there in minutes, which is awesome from a security standpoint. However, replacing a window is still a huge pain. To to prevent future window bashings, clearly I need to install a motion / field disturbance sensor to trigger some type of warning chirp that lets these clowns know that yes, it is in fact a real alarm system. The DEI 508D Field Disturbance sensor seems to be the ticket; my alarm system even has the 4-wire optional sensor connector port, so this sensor would be plug-and-play. Here is my problem: I don't want my 2-way key fob waking me up with the Warn Away alert every time somebody walks a little too close to my vehicle late at night. I would like to chirp or activate the alarm briefly, even if only for a second, but I don't want a key fob alert if this sensor is activated. My initial idea is to cut the Warn Away wire from the sensor harness and divert it to a relay that would power the alarm, but I am not sure if that would work or not. My question to you fine folks on the forum is "Would that work?" This sensor has four wires: Red, Black, Blue and Green. Red and black are 12v constant and ground, and I believe blue is full alarm (instant trigger) and green is Warn Away. Correct me if that sounds wrong. I have a relay I am planning to divert the green wire to that would send power to the alarm when the green wire is powered. Can anyone give me the thumbs up on this plan of action? Thanks!

There may be ways to do what your attempting but I don’t know enough about it to help. Another idea might be a less expensive alarm added with the existing one that only has the field disturbance sensor and it’s own siren. Could probably be armed and disarmed through the main 2 way alarm with some combination of the extra wires. Just omit any connections that would communicate to the 2 way alarm that the field sensors in the 2nd alarm were triggered. Then if the thief ignored them and smashed something the main alarm sensors would still trigger and tell the 2 way remote. Just an idea.Steve G

Hi Iskidoo, Thanks for the reply! I read the 508D install manual (the only bit of literature of any type I can find about this sensor) here: www.directeddealers.com/manuals/ig/accessories/2508111_508D_Installation_Guide.pdf It suggests you can connect the Warn Away (green) wire to a relay that would power the siren. It indicates that this wire provides a 500mS (half second) pulse that would trigger a short chirp when connected to a relay. However, both the green Warn Away and blue Instant Trigger wires are 200mA ground signal wires. What I believe this to mean is that the both the 30 (Common) and 86 (coil control) wires would need to be hooked up to 12v constant power, and the 85 (coil ground) wire would need to be hooked up to the green wire. I did a lot of research online and it seems there is no problem with using the ground side of the relay coil to control switching. I also searched and found this website which indicates automotive relay coils typically draw 150-200mA of power: https://www.electronicspoint.com/forums/threads/amp-draw-of-coil-based-relays.31449/ So hooking up the green wire to the coil ground wire should work fine. However, because the relays I purchased are inexpensive (Amazon EPauto), they don't have flyback/clamping diodes to protect against voltage surgess. Because of this, I am at the very least going to install a 5 amp fuse between the relay load wire and the siren power wire. I'd like to protect the green sensor wire too, but am not sure how to do it or even if it's necessary. If anyone has any opinion on my current plan of action, or suggestions on how to protect the siren and sensor from relay voltage spikes, please let me know. PS: I already tried installing one of these 508D sensors and it seemed to be faulty; couldn't get it to trigger 1st stage Warn Away at all; only full alarm. I sent it back and got a replacement; will see if this second one behaves properly.