New power lock switches, but still the same problem

[98redxlt]

Hello I am posting because I dont know what else to do but do not want to take my truck to a mechanic and pay for them to look at it. I recently bought new front power lock switches for both passenger and drivers side doors. The passenger side works fine but the drivers side does not lock the doors. It will unlock but wont lock them. This is the same problem I had before and is the reason I bought them. I used a test light and when I passed over the wires to unlock the doors, they unlocked. Once I passed it over the wires to lock the doors, it didnt light or lock them. Does this mean I have no current or power flowing through those wires to lock the doors? What else could it be? Any info or other ideas will be appreciated.
Thanks
Jeff