All doors will lock but none will unlock

[Goblin]

I just picked up a 2006 3500 dually this month and everything is fine except for little things here and there. The most annoying thing right now is my power locks. At first I would press the unlock/lock buttons from the fob and either the lights would flicker or the horn would sound (normal stuff) but the locks on all doors would do nothing. Tried using the switches on the driver and passenger doors, and still nothing. Well that turned out to be a blown 20amp fuse in the #2 spot.

So I replace the fuse with a spare and all of the doors lock fine from the fob and from the switches on both doors, but none of the doors will still unlock. I can hear the actuators working when I press the unlock buttons on the fob and switches but the knobs will not move from the locked position. I'm pretty sure its not all four actuators considering I hear them all working and they all lock into the down position perfectly fine. But why wont none of the actuators lift the knobs?

 

[PuffTheMagicDragon]

Edit: Completely forgot to ask if the locks are factory or not. All the info i posted below applies to the factory locks. If the system you’re using is aftermarket, it could be any number of things.



Check your battery voltage and make sure that it is healthy. If its on its last leg then it could be struggling to put out enough juice. Down might be easier to handle with gravity and all, and the higher load to push them up is too much.

Couple oddball options here for you, it is entirely possible that all four actuators are getting weak, or that when the fuse blew there was damage done to them or something along those lines. Possible, but seems unlikely.

Lastly, and hopefully not the issue, if all four locks arent actuating up, then it could be the output signal from the instrument cluster isnt as strong as it needs to be. The locks are multiplexed (BUS’d) through the speedo, so if you can hear all four trying to go, but failing, it might be an internal issue with the cluster. Each lock is individually driven on its own circuit by the cluster from a common power source, so if all four are failing to actuate, i would think the common thread would be the cluster.

Hopefully someone else will chime in with a simple ‘duh’ fix that i overlooked.

Good luck!