1988 GMC door locks
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=79423
Printed Date: May 18, 2024 at 12:47 PM
Topic: 1988 GMC door locks
Posted By: ofwes
Subject: 1988 GMC door locks
Date Posted: June 21, 2006 at 7:16 PM
I have shaved the door handles from my ride and they work great. I have installed the outside safety button to get me in when I close the keys inside. What I don't know how to do is wire the door locks to open when I forget and lock myself out.
Anyone have experience with this truck ? I can provide the diagram for the door lock circuit.
Thanks
ofWES
Replies:
Posted By: bjordet
Date Posted: June 22, 2006 at 3:34 AM
If I remember right, your truck has 5 wire reverse polarity locks which can be spliced in at the driver kick panel. You'll have to use a two relay setup to connect a keyless entry/alarm system to them. pull the driver kick panel off and there should be an access hole behind it at the bottom, just large enough to put your hand into. You'll feel a wire harness about the thickness of a roll of quarters. Usually there is enough slack in it to pull it down to the access hole and do your splicing there, if not you can also get to it where it comes out of the kick panel above the e-brake pedal, under the driver dash speaker. you'll have to cut the cover off the loom to expose the wires. you can catch power and the lock wires all in the loom. Once you have found and exposed the loom just follow the diagram for 5 wire alternating locks and connect to the light blue wire and the BLACK/ white wire. When you put your tester on them you should get 12volts at the blue wire when you push the driver door lock switch and then 12 volts on the BLACK/ white wire when you push the driver door unlock switch.
Posted By: ofwes
Date Posted: June 22, 2006 at 6:31 PM
Thank you for the valuable info. I will test this out in the AM after I get another relay. I'll let you know how it goes.
ofWES
Posted By: jhull
Date Posted: June 22, 2006 at 7:43 PM
I always unlock the door then take out the lock so it cant be locked again... why do you need locks if theres no handles? lol
Posted By: Chris Luongo
Date Posted: June 23, 2006 at 2:45 PM
I've only done locks on one of those trucks, but from what I remember from my friend's '90 pickup....
Getting the doorlock wires in the kick panel is difficult, but if you remove the left-front dash speaker, they're in a harness in there, with a lot more room to work.
Posted By: ofwes
Date Posted: June 25, 2006 at 6:37 PM
bjordet
I tried this using one relay to just unlock and had a positive result when the lock was already unlocked....but, when I locked the door and tried again, I blew the fuse.
Here are a couple of questions:
Do I have to use 2 relays?
Will this circuit disable the current switch or work in conjunction with it?
Am I cutting the black and white wire in half and inserting this circuit between the ends or leaving the wire whole and tapping on to it?
Any info is greatly appreciated.
Thanks
ofWES
Posted By: bjordet
Date Posted: June 26, 2006 at 1:59 AM
If you only want to unlock the door and not lock it then you can use only one relay. You will have to CUT the unlock wire and connect the switch side(coming from the door) to pin #87a on the relay, connect the motor side(going up kick panel or toward center of dash if you tap in under driver front speaker) to pin #30. Connect a constant 12volt (+) lead to pin #'s 87 & 85. That will leave only one pin left on the relay, #86, to connect to the (-) pulse unlock lead from your keyless entry/alarm. If you want to hide an external swith, use a waterproof 2 pole momentary switch and connect one side to a solid ground point and the other lead to pin #86. This will provide a negative pulse when pushed which will trigger the relay to unlock the door. Your factory door lock switches will function normally after connected. If you want to lock and unlock then you will have to use 2 realys, tape or stap them together and connect the second relay like it is a mirror image of the 1st one. the diagram on this site is exactly how your will look when finished. 5 Wire Alternating 12 Volts Positive Door Locks https://www.the12volt.com/doorlocks/page3.asp#5w Hope this helps.
Posted By: ofwes
Date Posted: June 26, 2006 at 7:55 PM
I appreciate the extra info. I sort of figured it out after I wrote you but am glad to have the confirmation. I was testing it incorrectly and trying to do it without cutting anything until I was sure what I was doing.
I can always add the door lock feature but with no handles, it will probably not be needed. I was just trying to prevent an the accident of locking myself out because of the where the switch is on the door and how much it looks like the window switches. I know there will be a time I will lock myself out and I won't like it. 
Thanks
ofWEs
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