73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Interior & Equipment => Power Windows & Door Locks => Topic started by: jhcon65 on December 14, 2010, 08:20:19 pm
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I have problem with the power door locks on my 87 Silverado .... they only work to lock the doors but not unlock ....I have tried different door lock switches and have pulled the ducting from under the dash to look around but , dont really know what I would be looking for ... I have a Chilton manual but its not help ,says nothing about the electrical system as far as the power doors are concerned.......any ideas ???? the truck has 407,000 k miles on it , and really has no problems just trying to get all the little bugs worked out ......
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just as a thought, have ya tried to pull the lock switches apart and tried to clean the contacts on it?
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yes , forgot to mention that.... fixed my tank selector that way took the whole switch all apart and cleaned the contacts worked great , but not for the door locks.....
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did the power locks always do that, or did they work right then quit?
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you know , Im not sure . As far as I can remember they USED to work but now that I think about it I dont know when they stopped....but yea , they used to , but who knows when that was ...I removed the acuators from the door and replaced them with another set I took out of another truck , but the same thing , they lock , but no unlock.....
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now just a thought, and im assuming you tried this already but did you check to see if it was getting power to the actuator when you tried to unlock the doors by any chance?
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Actually , no I didn't check that , I figured tat if there's power to lock it there must be power to unlock
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ok, it was a thought.
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Just because you took the switch apart and cleaned the contacts doesn't mean the switch is making contact in the lock and unlock positions. I would do as mentioned and check for 12v at the actuator when you press unlock on the switch. Either that or hot wire it and see if it moves in both directions. Its likely the switch or actuator, so it shouldn't be hard to eliminate one of them. Do you have a multimeter?
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Yes , I do have the multimeter , and will definately check that , but I have tried 2 other switches from trucks that I have gotten parts off of and same thing .... but asap i will check the switch and wires ... A much appreciated thank you in advance ..... Jeff
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OK , couldn't find the multimeter , but used a test light to test the actuator and the switch , No power to the actuator from the switch . No power when jumped from the exposed terminal on the switch to the unlock terminal going to the actuator . Traced the wires from the door up into the wire loom ... cant seem to find out if there is a relay or what up in there .....there is a a small black plug type thing that the wires from the door go int but not sure if thats a relay or just a connector .... is there anyone that knows where I can find any information about the location of the door lock relay or a fuse or someting ...up in there . So long story shorter .... no power to the door switch , and already checked the fuse block but at aloss as to where to go from here
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You have power to the switch because the door lock actuator locks the doors. Use your test light to find out which wire is hot all the time at the switch. Use your test light to figure out which wire becomes hot when you press the switch to the lock position. If the remaining wire isn't hot when you press unlock on the switch your switch is bad.
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If I jump the known hot wire to the lock terminal ( by passing the actual switch ) the doors lock . But if I jump the known hot wire to the unlock terminal , again bypassing the actual switch , I get nothing . This was accomplished by sliding the switch partly on the door lock wires coming out of the door. I have tried 2 other switches and still nothing . This problem is the same on both doors of the truck , lock from either side but no unlock from either side......
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O.K., unplug one of the actuators and run a 12v wire and touch one of the terminals with it, then touch the other. One should lock, one should unlock. If its doesn't do both then the actuator is bad. Do the same on the other door. I don't think there are any relays in the circuit. The only causes for this I have run into are bad switches, bad actuators, or corroded connectors.
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///////Do NOT apply 12v+ to the ACTUATOR connector/////// The terminals are normally grounded thru a relay under the dash and if you touch power to them it will be a dead short and you will have made more work for yourself.
The lock switch triggers a relay that applies power to one terminal of the lock actuators while keeping the second terminal grounded. When you flip the switch the other way the relay supplies power to the second terminal of the actuators and keeps the first terminal grounded making it unlock.
I'm guessing you have a broken wire in the doorjamb. Pull the boot back and check the wires close. The copper strands can be broken but the insulation can still be holding the wire together.
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O.K., unplug one of the actuators
As long as you unplug the actuator its fine. You do have to ground the other terminal, though (I didn't mention that). I haven't had the broken wire in the door jamb, although I could see that happening. I have had the switch, actuator, or corroded connector cause problems dozens of times on different gm vehicles. I was just trying to point him to what I feel like is the most likely cause. I'll bow out of this at this point.
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I actually did just as you mentioned , with the actuator plugged in , and I also removed the switch itself , and used a jumper wire to go across the terminal in the pig tail coming out of the door ..... In both cases , the actuator would lock , but when jumped to the unlock terminal the actuator did nothing . So , I've tried 4 switches all with the same result , so it's not the switch. I've tested 4 actuators , all with the same result ,so I've eliminated that .... I will next try to trace the wires for possible damage . ....all fuses are intact none blown . Can the relay go bad ? Are they the little black connectors that the wires go into under the dash ? 3 wires in 3 wires out ? .... The only thing that I didn't do , simply because I didnt feel it was warranted ,was to test the actuator wires at the actuator while trying to unlock the door to see if power was making it there.... Why not ... Because I jumped the wires at the pigtail and got no reaction .... Soo if it did not unlock while jumping , the actuator wires would also not be getting any juice ...... Please understand ,ANY AND ALL Information is valuable ... And greatly appreciated .......I hate electrical !!!!
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Ok .... Why would it effect both doors ? I checked the wires from the doors and found nothing ..... Should I just start replacing the relays? This gets really frustrating.... Any ideas on where to go from here
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The first place you start is with a schematic....
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Ok thanks....
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Here's a previous thread real similar to your problem.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=11943.0
But his truck was an 85 and the wiring schematic shows a relay. The schematic provided by Vile for your 87 shows no relay.
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I'm gonna back up here and say the truck does have a relay for the door locks. The maint manual for 1987 shows it to be located on the r/h side of the brake pedal bracket ( inside the cab). It's strange that it's not shown in the elect. schematic. ??? I think I'll go outside and check my truck...
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.... Ok , although i have worked on these trucks off and on through my life this electrical makes me feel just plain dumb ..... SOO i asumed the all to familair feet out the door , laying on my back , head jambed up on the floor board trying to look up under the dash ....position ... and then realized after fighting with the ducting ...for the vents /ac/heater......I dont know what im looking for !!?? Likes its going to have a giant lable on it that says "DOOR LOCK RELAY "..... ANYWAY ...... is it in the same area as the buzzer that comes on when the key is inserted ? cus i found that ....and lets just say that I do find it ... how do i test it , jump the wires across it ? to eliminate it as see the results ? any one have a picture of one so that way i at least I know what to look for ..??
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You are taking the wrong approach to this problem. First always go right to the source of the problem. In this case the door lock actuators and a test light. Before you do that as mentioned already the most common problem is broken wires in the jumper harness between the door and the jam? Did you check that?
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Here is another schematic for you as well
(http://i6.photobucket.com/albums/y228/Sabaka454/power1.gif)
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Nice wiring schematic! First-do what autorpr and Vile said- look for a broken wire at the door jam.
2nd- You found the relay center, but not the door lock relay. It's right behind the metal panel with the round ignition buzzer, closer to the firewall, higher and harder to access (of course). It has lt. blue and black/white wires on one connector and grey and brown wires on a second connector.
Hope for a broken wire at the door jam to be the problem.
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We've had some bad weather here lately , and me with only a single carport that the wifes car gets... I ve not had a chance to work on it....but still am trying to figure this out , How could it affect both doors and not be a relay ? Am I assuming that there could be broken wires on both doors ?...... When the sun comes out ill tackle it again.....
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jhcon65, do your power windows work ok? The reason I ask is because the relay controls both the door locks and the power windows circuits. If the windows weren't working, and the door locks either, then I would look at the relay. I didn't notice this until I looked at Vile's 2nd schematic.
It is possible that both door lock wiring circuits are broken- since you already eliminated the switches and actuators.
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yes on both doors the windows and "unlock " features have no problems ,and work fine ..... the rain and cold have subsided for the meantime so Im going out now to look at the wires from the door to the cab , will i have to replace the boot between the two once i have checked it? ...its rivited in , ......im almost to the point where i dont care if I fix it or not ......as always thanks in advance.....jeff
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Don't give up! You're almost there! Soon as this is fixed you're going too be the resident expert on it Jeff!