tilt sensor only

IS there any way I can just add a tilt sensor, and by using a relay that switches ground to the sensor with ACC/IGN, send a signal to the horn??

I dont really need/want to install a complete alarm system if I dont have to. I just need the tilt alarm.

I figured if I wired relay as following: 85 ground, 86 Ign/Acc, 30 ground, 87A (normally off) to tilt sensor ground. That way when ign is off, the ground to tilt sensor is 'on' and sensor would be armed.

I would then take output of sensor and wire it to horn/siren.


Does this make sense? WOuld that work?

Yes it would.
But diode across 86 and 85, 1N4004 band towards 86 otherwise you'll kill the sensor.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

I am not sure if I follow the need for the diode?

85 and 86 operates the coil with 85 to ground and 86 coming from IGN/ACC... When coil is open (IGN/ACC off), the ground would be not interrupted and tilt sensor would operate since 87A is the normally off post. With the coil closed (IGN/ACC on), post 87A would not be connected to ground anymore and the sensor would not operate (when driving...)

I understand that the diode blocks current flowing in a certain direction but what would the diode do between 85 and 86?

Great if you could explain to me as I dont want to ruin the sensor or cause issues with the wiring in my truck

When a relay shuts down, it sends up to 200 volts as a back EMP towards the sensor, along the 85 line, frying it.
Placing the diode there acts as a "quenching" device.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

ok, even though it is only ground going from relay to sensor?

With the diode, I guess i would protect the vehicle wiring as the only voltage from truck comes in at 86 on relay and with 85 wired to ground?

If the diode was between 87A and sensor it would kinda make sense although 87a only provides ground..?

No it's the coil 85 and 86 that sparks on shutdown.
In fact study your history "spark gap" radio transmitter back to Marconi.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Read this:-
https://www.bcae1.com/relays.htm

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

very interesting reading, much appreciated, thanks!

Well. That didn't really work. The trigger output from the sensor doesn't seem high enough to activate a relay. Without ground, the blue wire outputs 11v but with the ground interrupted, the voltage drops to millivolts.

Would there be another way to use the sensor without adding a full alarm system?

Sorry, should have mentioned that at the start, AFIK, none of these add-ons will work without an alarm system.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.