Why 2 ignitions?
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=28120
Printed Date: July 27, 2025 at 5:32 AM
Topic: Why 2 ignitions?
Posted By: markcars
Subject: Why 2 ignitions?
Date Posted: March 10, 2004 at 10:51 AM
Why are there 2 ignitions in cars? ANyone knows?
Replies:
Posted By: cbag1
Date Posted: March 10, 2004 at 1:21 PM
it depends how the vehicle design, mostly 2nd, 3rd ignition will power up fuel and hydraulic system of the vehicle. if you ignore to power this wires might fry your transmission and causing fuel pump inoperable.
Posted By: markcars
Date Posted: March 10, 2004 at 3:54 PM
I have 2 ignitions and remote-started with only feeding 1 ignition. I've done this for 2 weeks now including driving after running car for 10 minutes each time. The car is working fine. does anyknow know for sure?
Is it ok to power both ignitions at the same time? (during remote starting?)
Posted By: cbag1
Date Posted: March 10, 2004 at 4:47 PM
If either one not draws more current it will be ok. But in proper way if it is more than one you split with relay.
Posted By: auex
Date Posted: March 10, 2004 at 10:14 PM
The seperate ignitions power seperate computers. That is why if you don't hook the third ign on a chevy there can be problems with the tranni, the transmission computer isn't turned on when it is supposed to causing the car to freak out.
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Certified Security Specialist
Always check info with a digital multimeter.
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Posted By: sroth140
Date Posted: March 11, 2004 at 3:19 AM
freak-out = bad. so just do it right.
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MECP certified installer
Posted By: markcars
Date Posted: March 11, 2004 at 5:53 AM
yeah, i know that I have to do it right and will too. Just wondering why the car has been working fine without it other than my ac/heater arent working. So I thought maybe the second one is feeding my heater/ac circuits. I will have to read my repair-manuals to be 100 percent sure. Thanks for all the inputs. I don't want my car to feak-out or go bad either.
Posted By: derek123
Date Posted: March 11, 2004 at 11:44 AM
They are isolated at the switch for a reason. The computer is fused at 10 or 15 amps. The Primary IGN is fused much higher than that. This is why it is never a good idea to jump them together. ( instead of using a relay) A good rule to follow would be, always recreate the action of the key, that way you can't be damaging the vehicle. ( always when it comes to IGNs, with ACCs, it is not as critcal, some times 2nd or 3rd ACC will just keep an airbag light or abs light off during RS) If it has 2 IGNs power them up. a SPDT relay cost less than a new ecu.
Posted By: markcars
Date Posted: March 11, 2004 at 12:07 PM
thanks for the info derek123. I have 2 igns.
Can you tell me one more thing, does the ign-2 give power to the ac and heaters? I'm still wondering if it is the second IGN or a second ACC that powers the heater and air cond. All diagrams on my car show 2 IGNs.
My radio is connected to 12v constant and to IGN. However, it comes on when I put the key in ACC. Thats what is confusing me.
Posted By: Legrones
Date Posted: March 11, 2004 at 1:39 PM
yes in most cars the secound ign powers the ac/heater when u remote start your car
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Dale / Cory
Posted By: Legrones
Date Posted: March 11, 2004 at 1:40 PM
yes u need to hook up your secound ing it powers the ac/heater
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Dale / Cory
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