I recently bought a 2002 f150 screw. The front passenger door lock gives kind of a rattle noise, something like it is trying to operate a half dozen times all at once. Is there independent relays for each door? Also all the locks seem to operate rather loudly. They work well enough but maybe a little too well!

 

It sounds like the actuator for that door needs to be replaced...
Let us know if that solves the problem. They are rather easy to replace.

 

Heres some info.

WARNING: The following is long winded, but if you want your PDL's to work again WITHOUT spending any $$ read on.

I finally got tired of my non-working PDL's and decided to tear into my truck and find/fix the problem. There has been many discussions about possible issues and I have concluded that the majority of us are seeing actuator motor problems and not relays, switches etc. Ill start by saying the problem I have had is that when I hit the switch, the locks attempt to move and after repeated attempts, the signal appears to get weaker and weaker until nothing....I assumed relay or switch.....NOT THE CASE!

First I started by testing the signal at the harness plug to the actuator. Perfect. No issues here. Next I completely removed the actuator/lock mechanism and bench tested them with 12V..Here lies the problem. The actuator acted the same as when in the truck. First I did a thorough cleaning of all of the mechanism so it works freely and still had the same results. Here's where it get's tricky. These things are built so that they are NOT serviceable. I had already decided that they were going to need to be replaced, so I decided to break them open for closer inspection. It comes apart relatively easily, but appears that It cannot be put back together once apart. I drilled out two small rivets and then pried the case apart. As you pry the case apart you'll notice these small little plastic rods protrude up through the case cover. These rods are then "mushroomed" with heat through the upper case and then sealed with some kind of silicone. When you pry apart the case the "mushroom" head breaks off and the rod remains. You can dig out the silicone and mushroom head with a pick. It comes out very easy. Inside you will find a very small motor and some gear mechanism. I believed the problem at first to be worn brushes or dirty commutator contacts in the motor itself. You'll have to bend two little metal tabs out and pull off the brush housing on the back of the motor. I cleanded the gunk off the brushes and took 1500 grit to the commutator contacts and reassembled the motor. The motor worked, but if you applied even a slight amount of resistance on the armature, it would stop the motor. It should have been WAY stronger than this. I was stumped until I looked a little closer at the inside of the plastic brush housing. Inside you'll find a small, thin rectangular (thermal resistor relay, dodad, thingamabob??) pardon my ingnorance, but I'm not sure what to call it. All I know is that this little part is what keeps you from burning up the motor, should you continue to press the switch once the lock has been actuated. It appears that this thing wears out over time and will not allow enough signal to get through to the motor to make it work. THE FIX. I am cheap. Since I had done so much work up to this point, I decided that I would go a little further and try to make it work without spending the $$. I have better things to spend my money on than actuators. I took a small piece of aluminum foil and wrapped the "thing" voila! Perfectly working motor! I sat there and operated the thing for 10 minutes including one or two times stopping the armature and holding down the switch to see what would happen. The motor builds heat, but not much. Not enough to worry about. Now that I had a good working motor I decided I would try and reassemble the unit. The problem is you cannot glue the unit together as there is a rubber gasket around the perimiter of the case and if you tried to glue the rods into the case, you would not have enough pressure on the two halves of the case to keep the gears in place (these things actually apply a great deal of torque on the case) What I decided to do is completely break off the plastic rods flush with the bottom side of the case and then drill out the bottom case and screw it together. This worked perfectly. You'll need screws that are the same diameter as the holes in the top of the case to keep it from "wandering". Also the screws should not protrude through the back of the unit as some of the mechanism has some pretty close tolerances and a screw sticking through the back would not allow some of the mechanism to work (this can be remedied with a decent set of wire dikes or a hacksaw). I know all of this is hard to picture, but if you do decide to try this fix, you'll see what I am describing here. The locks are back in and working flawlessly.

 

That fix is out there with pics if you google "sluggish door locks"
I fixed both mine that way and they worked flawlessly.... for about 3 months. Then they both went within a day of each other. They now make the sound that the OP described. It crossed my mind that perhaps the previous owner had attempted the fix as well.
Not sure...but for the price of the actuators at Rock Auto I would not bother. I have 2 in my cart and will get them once I have a few more parts to justify the shipping. I still want to pull the others out and find out what made them fail the second time.
It sounds like something is stripped inside.

 

we carry the door lock actuators for your truck.here's a link to them on our site if you end up needing one and would like to check on pricing.

F150 Ford Truck Door Lock Actuator