Want radio to stay on without key
Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=1892
Printed Date: May 15, 2025 at 9:05 PM
Topic: Want radio to stay on without key
Posted By: inst1664
Subject: Want radio to stay on without key
Date Posted: July 12, 2002 at 8:54 AM
help>????????? In newer GM cars the radio stays on when you take out the key until you open the door. Does anyone now how to configure this this system because i want to put it in my girlfriends 1990 corolla? I tried using the momentary to constant relay diagram, it works and stuff but doesn't shut off. I added a relay to deactivate it when the door opens but then if the car is running and someone opens the door the radio shuts off. Does anyone know what to do????? Help me please........... Rob
Replies:
Posted By: go2pac
Date Posted: July 12, 2002 at 11:21 AM
If your girlfriend has an alarm then use this diagram which will give you more control... https://www.go2pac.com/misc/miscdiagrams/latchrelay.pdf ------------- Karl
Pacific Accessory Corporation
Mobile Audio Interfacing Equipment
Connecting You to Your Music Since 1976
Posted By: sparkyssb
Date Posted: July 12, 2002 at 1:24 PM
What if you don't have an alarm? I'm interested in this myself. thanks.
Posted By: the12volt
Date Posted: July 12, 2002 at 2:17 PM
Rob, on the relay you used to disengage the latch, connect the 12V+ going to the coil through the normally closed contacts of another relay activated by the vehicle's acccessory lead so it will only allow 12V+ to pass to the coil of the first disengage relay when the key is in the off position.... You'll want to connect the four relays as folows: Relay 1 (engages latch):
85 = 12V+ Switched (accessory)
86 = Ground
30 = 12V+ (constant)
87 = connect to 85 & 87 of 2nd relay
87a = not used
* place diode across coil with cathode towards 85 Relay 2 (the latch):
86 = connect to 87a of 3rd relay
30 = 12V+ (constant)
87 = as described above with Relay 1 and to the accessory lead of your head unit
87a = not used Relay 3 (Relay 3 & 4 disengage the latch only when a door is open and the key is off):
85 = (-) door trigger
86 = connect to terminal 87a of 4th relay
30 = Ground
87 = not used
87a = as described above from Relay 2 Relay 4:
85 = 12V+ (switched accessory)
86 = Ground
30 = 12V+ (constant)
87 = not used
87a = as described above from Relay 3 If you need a diagram, let me know and I'll try to draw one for you this evening. the12volt
Posted By: inst1664
Date Posted: July 12, 2002 at 2:46 PM
thanks thank thanks thanks thanks..... Actually i figured it out using only 3 relays.... for now it works 100% on the test bench, i will also try the 4 relay way, it looks a bit more safe for the car. thanks a whole the12volt... I'll work out the diagram rob
Posted By: the12volt
Date Posted: July 12, 2002 at 3:46 PM
Hi Rob, you're welcome, glad I could help.
Posted By: go2pac
Date Posted: July 12, 2002 at 5:21 PM
Yes it will still work with out an alarm. Just connect the door trigger(-) to relay#4 pin 86 instead of the doorlock(-). But in that case you can make it more simple, you can use just 2 relays and two diodes... https://www.go2pac.com/misc/miscdiagrams/latchrelayrap.pdf the relay or diode above the radio is to prevent the latched relay #1 from feeding back into the rest of the vehicle. If the radio draws a lot of current from the accessory wire, use the relay method. If its very low current draw then you can use a 1-3 amp diode. ------------- Karl
Pacific Accessory Corporation
Mobile Audio Interfacing Equipment
Connecting You to Your Music Since 1976
Posted By: sparkyssb
Date Posted: July 12, 2002 at 10:22 PM
I am confused on the above diagram by go2pac..... im asumming the middle pin on any relay is NO? and the outer pin (not common) is NC... right? Then that means the 2nd relay will give 12power each time the door is closed..but relay 1 will stop it from going in the radio through the acc. line. To my knowledge...it looks like it will never give power to the radio when the ignition is off, even for a short period of time. Relay 1 switches off right after the accessory line is done recieving a + signal... What am I studying wrong? (BTW...its like 12:20 in the morning so I'm a little out of it as it is... hehe... thanks guys.)
Posted By: go2pac
Date Posted: July 13, 2002 at 10:27 AM
The middle pin 87A is normally closed and the top one is 87 normally open. Ok, when you get into the car and close the door, turn on the key, relay 1 will latch and radio turns on. When you turn off the key, relay 1 will still stay latched and radio still stays on. When you open the door, relay 2 will energize and relay 1 will no longer recieve 12v so it will unlatch and radio turns off. Now if the door is open and you turn on the ignition, it will turn on the radio and relay 1. Relay 2 is also energized and cuts 12v to relay 1, but that will not affect anything since the radio will still get power directly from the ignition. If you turn the key off, then the radio will turn off immediately. ------------- Karl
Pacific Accessory Corporation
Mobile Audio Interfacing Equipment
Connecting You to Your Music Since 1976
Posted By: sparkyssb
Date Posted: July 14, 2002 at 9:26 AM
Ok...now I get it...thanx! Now, one question...the accessory wire on the radio....is that the same as the blue wire that goes to my amp? or is that the actual 'radio' 12v power wire?
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