Hello this is my first thread. Just a few days ago I purchased a 90 f150 lariat xlt with 5.0 automatic. Everything seems to work great and low kilometers. One problem that I have run into is the power lock switches don't work on either side. I know the power locks work though since it has keyless entry (aftermarket) and it works fine. Has anyone else ran into this problem before? If so can you lead me into the right direction so I can get this problem solved. Thanks in advance
-Brad

 

Get new door switches they might be worn. If your fairly electrical inclined tear into the switches and fix the contacts. If not go to a pull a part and get new switches. While your there I'd look for any other parts you might need.

 

Don't buy anything until you test the system. Your aftermarket setup is likely causing the issue. Get a DMM or a test light will work OK and pull the door panel. The factory used a simple momentary switch system. 12v into the switch, ground at the actuator. Push one way 12v to the open part of the actuator and other way to closed. We know 12v is getting to the aftermarket system because it works. We can eliminate the actuator and ground also. So you need to make sure constant power is making it to the switches and from them to the actuator. My guess is that the po cut the power wire and connected it to the remote system eliminating the switches.

 

Thanks guys for the quick response. This afternoon I will start ripping off the door panels tonight after school. I will keep you guys posted!

 

This is the switch wiring. To the right of the picture is for the locks


There are 5 wires at the switch for unlock lock function. Grey wire to the back left wire will lock. To the right of it will unlock. Grey wire to the front pink one to the left wire lock and the one next will unlock. Why is it wired this way? Is it the switch that's faulty as I can jump them? If so why would both sides be caput? Thanks guys

-Brad.

 

I can almost hear crickets on this thread haha. Do you guys think it's a wiring problems or just simply a switch? I proceeded to take off the door panel on the drivers side and I can't lock or unlock via jumping the wires I just get sparks. I'm lost now

-Brad

 

Sorry I was looking for a wiring diagram. Your going to have to check the wires with a meter and do some tracing unless you can find a diagram. Do you see the remote unit tied in anywhere? One switch is the door and the others are windows right? The center should be power and the others should be output to the door actuators. Find which one has power and try jumping to the one leading to the actuator. Of that works its the switch. If not check the wire to the actuator. Switch it and check for voltage at the actuator end. Disconnect the end at the actuator and check for a short to ground.

 

Well it's definitely the switch. I called up a local pick and pull and they said 25$ for each side. Or do you think I should buy brand new switches just for the fact that used ones can go wrong right as fast as this one has?

 

I haven't had any trouble with the used ones but for $25 I think you are close to new price.

 

Yea I hear you. We'll if I'm close to new price I might as well give 10 or whatever dollars more and get brand new and have no worries