power door lock

[plinkie]

2000 gmc sierra. The passenger door lock will lock from both doors. But it will not unlock from drivers door or passenger door. I have removed the door panel, and when you push the unlock button, drivers door unlocks, but passenger door has no sound at all, as if there is not power going to it. If I manually unlock it and push the button, it will lock, but again, won't unlock. The passenger door operates the drivers door with no problem. So to sum things up, drivers door locks/unlocks from either door switch. Passenger door will only lock from either door switch. Any suggestions?? Thanks

[RCH]

I had the same thing happen on my 91 Sierra, ended up being a bad switch on the passenger side door. You can test the switch to verify. Mine had five wires, one Positive, one for up, on for down, and I believe the other two completed the circuit to the other side. With a voltmeter, connect Red test lead to hot wire, (should be the wire in the middle). the others are easy to figure out. Push button up and down to determine if current is being interupted through the switch. I purchased the switch and it cost about $30.

Mine is a negative lock system, meaning that the poles are always hot and pressing the switch grounds to activate it. So you should always read 12 volts when the switch is not being pressed, then when you press the switch voltage should be interupted causing the lock to activate up or down. Hope this helps.

[plinkie]

I had the same thing happen on my  91 Sierra, ended up being a bad switch on the passenger side door. You can test the switch to verify. Mine had five wires, one Positive, one for up, on for down, and I believe the other two completed the circuit to the other side. With a voltmeter, connect Red test lead to hot wire, (should be the wire in the middle). the others are easy to figure out. Push button up and down to determine if current is being interupted through the switch. I purchased the switch and it cost about $30. 

Mine is a negative lock system, meaning that the poles are always hot  and pressing the switch grounds to activate it. So you should always read 12 volts when the switch is not being pressed, then when you press the switch voltage should be interupted causing the lock to activate up or down. Hope this helps.

 

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I found the problem. It was the unlock relay in the fuse box on the drivers side of the dash. Thanks for the reply

[plinkie]

I had the same thing happen on my  91 Sierra, ended up being a bad switch on the passenger side door. You can test the switch to verify. Mine had five wires, one Positive, one for up, on for down, and I believe the other two completed the circuit to the other side. With a voltmeter, connect Red test lead to hot wire, (should be the wire in the middle). the others are easy to figure out. Push button up and down to determine if current is being interupted through the switch. I purchased the switch and it cost about $30. 

Mine is a negative lock system, meaning that the poles are always hot  and pressing the switch grounds to activate it. So you should always read 12 volts when the switch is not being pressed, then when you press the switch voltage should be interupted causing the lock to activate up or down. Hope this helps.

 

<{POST_SNAPBACK}>

 

 

 

 

I found the problem. It was the unlock relay in the fuse box on the drivers side of the dash. Thanks for the reply

 

<{POST_SNAPBACK}>

 

 

 

[RCH]

Electrical issues can be pretty difficult sometimes with so many variables. Glad you solved it.