Horn goes off intermittently after dead batteries changed
 

2000 F350 crew cab, 7.3, Lariat, manual trans,

My 7 year old batteries got real low. major clicks only. They refused to take full charge on battery charger so I assume they are just toast. I changed the batteries now the horn goes off intermittently when sitting and you can hear a solenoid click inside the engine compartment on the passenger side. All this without the engine started. Engine starts fine, truck runs fine. Talked to the dealer and he said it most likely was the security system and was related to a door lock actuator. All four of my door lock actuators have failed over the years (had the truck since 2002) so I just use the key to get in for years now. Has anybody seen this? My thought is that the factory security system (no add on) just needs to be reset since it worked fine for all those years without the door lock actuators working. How do I reset the system? My keys are the old small head type I really doubt there is a chip in them.