Missing power door locks
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Joined: Sep 2013
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From: Sacramento, CA
Missing power door locks
Although I own several old Ford trucks my newest a 1991 F350 crew cab seems to be the toughest to find information on. The truck came from the factory with power windows and door locks in the front doors. For children's sake apparently someone move the front door locks to the back doors and they work fine. No switches in the back doors. I want to install door locks in the front again and keep the locks in the rear as well. I have tried to do this to no avail. There is factory wiring harness for the locks in the rear doors and I have power to the wires that were cut when the locks were moved to the back doors. however when I hook up a power door lock motor I get nothing. I have a wiring manual for 1991 F series trucks but it does not include the crew cab. any thoughts or suggestions?
Thanks, Robert
Thanks, Robert
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Joined: Jun 2004
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The power door locks work by reversing polarity on the two wires to the motor. The switch does this, positive and negative are switched to lock or unlock. I'd have to check my Haynes, but IIRC both wires are always grounded until you hit the switch, then one wire is decoupled from ground and given power. Power and ground are sourced at the switches.
You mention you have power at the cut wires in the front doors - is that constant or when you hit the switch? Do you have ground at those cut wires?
You mention you have power at the cut wires in the front doors - is that constant or when you hit the switch? Do you have ground at those cut wires?
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New User
Joined: Sep 2013
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From: Sacramento, CA
There is power to the wires only when the switch operates and the ground goes to the switch as it is shown in the wiring diagrams. I do understand the somewhat backwards way the system works.
Mountain Pass
Joined: Aug 2019
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check the voltage make sure its enough to run all 4 locks? if you are getting power it should move the actuators. be it 2 or 4 as long as there is enough to push it. try the actuators on a battery make sure they move. fords are bad to lock up. my broncos dont move at all.
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