87 Silverado power door lock prob

[jaredts]

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.

[jhcon65]

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 !!!!

[jhcon65]

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

[VileZambonie]

The first place you start is with a schematic....

[jhcon65]

Ok thanks....

[DnStClr]

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.

[DnStClr]

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...

[jhcon65]

.... 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 ..??

[VileZambonie]

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?

[VileZambonie]

Here is another schematic for you as well

[DnStClr]

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.

[jhcon65]

 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.....

[DnStClr]

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.

[jhcon65]

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

[DnStClr]

Don't give up! You're almost there! Soon as this is fixed you're going too be the resident expert on it Jeff!