Did I fry my trunk release?
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=62509
Printed Date: July 13, 2025 at 6:32 PM
Topic: Did I fry my trunk release?
Posted By: jcman311
Subject: Did I fry my trunk release?
Date Posted: September 10, 2005 at 11:24 PM
Commando FM 870 that I installed myself. This is my third alarm install and all of gotten more involved as I have progressed. Problem is that the other day I was stopped at a light and my trunk popped. Didnt think anything of it until I went to pop the trunk today and neither the remote to release or the switch in the car to release the trunk works. I have the output of the alarm to a relay to the trunk release in the car. Wired constant 12V to the 86 and 87 terminals, and the output to 30 and the alarm input to 85. I havent probed the relay yet so I hope the output from the alarm isnt fried. But being that the button to pop the trunk in the car doesnt work, I think I fried the trunk relay in the car. Any input to this?? Thanks and great forum!! ------------- 1994 Mercury Grand Marquis
Alpine Audio
Replies:
Posted By: auex
Date Posted: September 10, 2005 at 11:38 PM
Check the fuse first.
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Certified Security Specialist
Always check info with a digital multimeter.
I promise to be good.
Tell Darwin I sent you.
I've been sick lately, sorry I won't be on much.
Posted By: jcman311
Date Posted: September 10, 2005 at 11:54 PM
All fuses are intact.
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1994 Mercury Grand Marquis
Alpine Audio
Posted By: auex
Date Posted: September 11, 2005 at 12:25 AM
Ok, then make sure that there is power going to the relay. If there is power going to the relay then take your meter to the alarm output and hit the button. If the pulse from the alarm is there then there is something else wrong, relay, connection to the vehicle, etc... If the pulse is not there then the output might have gone bad.
-------------
Certified Security Specialist
Always check info with a digital multimeter.
I promise to be good.
Tell Darwin I sent you.
I've been sick lately, sorry I won't be on much.
Posted By: jcman311
Date Posted: September 16, 2005 at 1:51 PM
Update... Power going to relay and the pulse from the alarm is still present. It seems almost like the relay is staying engaged for some reason. When I take the power away from the relay, the trunk release button in the car works again. Hook up the power to the relay and the remote release will work for a few times, then with the car sitting for about an hour the relay will pop the trunk and then I believe the relay will stay engaged because neither the remote release nor the button in the car will work anymore. Any ideas? Thanks. ------------- 1994 Mercury Grand Marquis
Alpine Audio
Posted By: iskidoo
Date Posted: September 16, 2005 at 4:09 PM
Did you try swapping the relay out with a new one? How long after the install did you notice this issue. hours? days? months?
What are you tapping for 12volts to supply the relay?
What is each pin of the relay wired to?
86 constant
87 constant
30 ??
85 ??
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Steve G
Posted By: jcman311
Date Posted: September 16, 2005 at 5:22 PM
The 12 Volt supply comes fused from the battery (5 amps). Havent tried swapping the relay out yet because I dont have any sources for good Bosch relays around here so I need to order some online. I noticed the issue started the day after I installed the alarm/trunk relay when I went to use the button inside the car and nothing worked. 86 constant 87 constant 30 to trunk solenoid wire (+) 85 from alarm output (200 mA - ) ------------- 1994 Mercury Grand Marquis
Alpine Audio
Posted By: iskidoo
Date Posted: September 16, 2005 at 6:29 PM
If your wiring is all solid and your not using T-taps or something then it sounds like the relay may be bad. Do you have any other relays from within your install? External ignition, acc. starter or starter kill relays that you can borrow to test with?
You could try swapping the wires on pin 87 and 30.
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Steve G
Posted By: jcman311
Date Posted: September 17, 2005 at 2:05 AM
Unfortunately (and actually luckily) its the only relay I've needed in the install. One more question though. Would it matter if the relay came with a diode built in? From what I understand if the relay has a built in diode and the ground (from the alarm) and power are switched it could cause the relay to be permanently on. Right now I just have the relay unhooked so that the factory trunk release inside the car still works. If I have time this weekend I may go out and do a little testing with the old multimeter. ------------- 1994 Mercury Grand Marquis
Alpine Audio
Posted By: iskidoo
Date Posted: September 17, 2005 at 8:05 AM
LOL...yeah you didn't mention that little detail before  ...remove the diode. it doesn't apply to this install. ------------- Steve G
Posted By: jcman311
Date Posted: September 17, 2005 at 5:44 PM
I dont think you understood my question. It was if the relay has a built-in diode. I cant remove a built-in diode. Although I dont believe the relay has one. I believe that I will try switching the connections on the relay later to see if that helps at all. I try and go for this. 87 to trunk release 86 trigger from alarm 85 constant 30 constant ------------- 1994 Mercury Grand Marquis
Alpine Audio
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