Problem installing an alarm in my 75.
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From: Fremont Ca
2022 C4 of the Year Finalist - Modified
Problem installing an alarm in my 75.
I'm in the process of installing an alarm in my car and the door pin switches will not activate the alarm. I've tried to different alarms,replaced the pin switches and neither will activate the alarm. I'd like to look into using the dome light to activate the alarm if I can figure that out. Any suggestions?
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From: mount holly NC
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Does this help?
#1 Apply 12 volts to make sure the horn works, if not apply a ground and recheck.
$2 check for 12 volts at the key switch and that the switch goes on & off.
#3 check for 12 volts on the pink wire at the relay and that the relay is grounded.
#4 check that the flasher works.
#5 Confirm the ground at both doors and under the hood.
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I've installed a number of alarms over the years. With motion sensors and all the bells and whistles. So I must say I'll be damned if I know the issue. Our door switches go to ground when activated. Perhaps your alarm is looking for power, and not a ground?
if this is the case. A second set of door switches mounted above or below the factory switches wired to provide power instead of ground could work if this is the case.
Wiring into the dome light doesn't sound plausible. Power is constant at the dome light and ground is provided by the door switch.
Perhaps if you could send me a Wiring diagram of this alarm I could walk you through the installation.
if this is the case. A second set of door switches mounted above or below the factory switches wired to provide power instead of ground could work if this is the case.
Wiring into the dome light doesn't sound plausible. Power is constant at the dome light and ground is provided by the door switch.
Perhaps if you could send me a Wiring diagram of this alarm I could walk you through the installation.
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Knowing what brand alarm you're working with would help. I've used numerous brands over the years in lots of gm's without issue, normally taping into the existing switches, I think only once I had to add a set of diodes because the alarm wanted a ground and couldn't deal with the fact that the switches had separate power going to them when the courtesy lights came on. That was the alarms fault, not the cars
M\
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From: Fremont Ca
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The OEM alarm will only sound a horn,won't disable the starter. This is really bizarre that the pin switch won't ground,activate the alarm. I can ground the alarm,it activates,I can touch the the pin switch which is grounded alarm activates. But it I tie the alarm into the pin switch,nothing. The pin switch is new,threads in door jamb cleaned for a good ground. This makes no sense,plunger comes in contact with the body of the pin switch,dome light comes on. I've named the car Evil Kermit for a reason. I've put alarms in my cars over the years,I'm a maintenance mechanic my profession and this is one nobody can figure out. The alarm in a Viper Model 3606V. According to the wiring harness the GREEN WIRE in the main harness is the correct wire for the door pin switch.
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Thread Starter
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From: Fremont Ca
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Yes,I have an alarm I pulled out of a car years ago in working order that I tried,everything works but the door ground pin switch on this car,worked in the past. It boggles the mind. The next test will be to pull the switch out of the door jamb,hook everything up,run a ground wire to the switch,wire up the alarm and manually operate the switch.
Last edited by Z51JEFF; Sep 24, 2022 at 04:42 PM.
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OK. So it sounds like the alarm is looking for a ground at the door switch. The fact that the switch has 12v. Going to it all the time is what is screwing you up. As stated above, add a diode before each door switch to cancel the 12V. In. only allowing the ground out. A diode before each door switch should solve your issue. As per the relay idea. That's out if your alarm is looking for a ground. Might want to place that diode between the switch and the courtesy lights now that I think about it. Don't need it backfeeding and grounding through the courtesy light circuit.
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I figured it out,poor ground at the door pin switches. I need to run a seperate ground for the pin switches. Thanks for the advice everybody,greatly appreciated.
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The issue was a poor ground at the door pin switches. It was just enough of a ground fir the dome lights to work but not activate the alarm. A separate ground to the main dash support fixed the issue.
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Glad to hear you got it Jeff. Dirty ground, yup, a light bulb may tolerate a dirty ground. But a computer sure wont!