Have replaced battery, alternator and starter and it won't stay charged. Note... the radio and clock do not work.
This is a common problem when the voltage regulator is failing which is potentially due to a faulty ground or connection. I would start by checking the battery connections and cables to be sure they are not dirty or corroded. Also, check the ground cable (black going from battery to chassis of truck) to be sure it is properly connected. Lastly, I would recommend having the voltage regulator tested. This is a unit that regulates the charging activity from the alternator to the battery. When this is not working properly, this can cause the battery to over or under charge resulting in it dying. Since there are a few things to inspect, I would recommend having a certified professional from YourMechanic come to your home to inspect the battery along with the other components mentioned.
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