Sometimes I go to start my truck and it will start and run fine but then when I go back to start it will not start because it acts like it has no voltage. All the lights in the dash are dim even the wait to start. It will not even have enough voltage to put my window up. I ca hear it clicking under the dash between the the steering column and the radio. Sometimes the clicking will go off and sometimes it will keep clicking for long periods. If I shut the door or just push in the button at the door it will quit clicking but still will not have enough volts to think about starting the truck. Is there a certain wire harness under the dash that is prone to having problems and could be shorting out? Thanks for any help!
Batteries are charged up and I did replace the starter selenoid on the fender about 3 months ago because of it doing this same thing. I hooked a charger up to it and set it to 225amps while trying to see if it would help it get enough current to start but no luck there either. I layed on the floor board and listened to the clicking under the dash but it was dark so I could not make out which item it was under there. I did wiggle a bundle of wires under there and it caused the clicking to stop and then I moved them back and it would start again. I will see if I can figure out where those wires go tomorrow in the daylight and get back with you. Thanks!
Along with the battery terminals and cable ends, also check where the ground cables bolt to the engine block, they need to be CLEAN and tight. The fender mounted starter relay is used for the power distribution point for all the power to the rest of the truck. Make sure the wires to the relay, on the side that has the cable from the battery on it are good, with no corrosion there.
Have you had the batteries load tested? Test them one at a time, not hooked together.
This is not a load test, but you can check some things out this way. Take a multi meter set to 20Volts DC, and check the voltage at the batteries, with the cables unhooked. you should get at least 12.5 volts. If that checks out, hook the cables back up and check the voltage at the starter relay on the fender. You shold have the same voltage as you get with the batteries unhooked.