87 Silverado power door lock prob

[jhcon65]

 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  ......

[87suburban]

just as a thought, have ya tried to pull the lock switches apart and tried to clean the contacts on it?

[jhcon65]

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.....

[87suburban]

did the power locks always do that, or did they work right then quit?

[jhcon65]

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.....

[87suburban]

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?

[jhcon65]

Actually , no I didn't check that , I figured tat if there's power to lock it there must be power to unlock

[87suburban]

ok, it was a thought.

[jaredts]

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?

[jhcon65]

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

[jhcon65]

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

[jaredts]

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.

[jhcon65]

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......

[jaredts]

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.

[autorepr]

///////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.