Im a rookie car alarm installer and although i personally dont do it, i noticed that alot of installers wire the alarms door triggers into the cars domelight switch. I was just wondering is this an installers preference or some specfic reason that it's wired that way?
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CEDRIC
This is a normal practice. But if YOU want to be different, You could run a wire to each door pin, and have to diode isolate each wire (in a lot of cars) some cars you would not need to use the diodes. The door pins control the domelight. The domelight is just easier because you only have to make the one connection.
But what if the alarm has a wire for domelight supervision(clifford) and door triggers, would you still connect the door triggers to the car's domelight switch?
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CEDRIC
In some vehicles you need to wire into each door pin and diode isolate them. Some factory dome light wires can be deactivated with a switch on the dome light or dash. Tapping into the dome light wire on such a vehicle wouldn't be the correct method because if the switch were in the wrong position, the alarm wouldn't respond to a open door. On some vehicles the dome lights won't come on during the day because the car senses the light level inside and won't turn them on with a door open. Some alarms won't arm properly if the dome light wire stays active for a time after closing the door. They may not monitor the dome light wire if they see it active while arming. The prefered method for all these reasons is to use each doorpin circuit. Sure the dome light wire is quicker in most cases, but if the alarm isn't installed well, it won't be a very effective system.
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sparky
c.c. autospa, the main impetus is the simplicity - all the alarm needs is a wire which will show ground or 12v+ when any door is opened.
It's an acceptable practice to connect the door trigger and dome supervision to the same wire. The reason is that the alarm only activates the dome supervision when it's either
1. just been disarmed, and the ignition hasn't been turned on.
2. actively going off.
In either of those 2 cases the alarm is not really concerned whether the doors are open or not.
The dome supervision should ideally activate a relay(if the alarm doesn't have an onboard relay) to the wire in the car that actually controls the domelight bulbs.
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C Renner's Auto Electronix
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