2003 Centennial only starts with a jumper

[Seahawk]

Hi. My 03 4.6l Centennial with 270,000 miles recently began not starting. It has a fast clicking of the solenoid. Easy to jumpstart and after starting will run as normal (everything is bright and works normally). Turn it off and it clicks again. Battery is two years old (yes, I always keep it filled with distilled water. I am not "that" guy). I have noticed the passenger side headlight sometimes has to be "helped" to turn on after getting truck started. I would normally think solenoid except it starts with a jump (same for starter). Terminals are all shiny and NO corrosion to be found. Ground problem somewhere? I am still looking and taking headlight apart when weather/time cooperate. Have you had this problem?

 

[IPcamper]

Sounds like the battery is not being charged properly or isn't holding a charge. Use a volt meter and check the battery with the cables disconnected. If it is fully charged it should read 12.7 volts, at 75% charge --- 12.4V, 50% charge --- 12.2V, less than 12V then It is discharged.
Then with the battery connected with the engine running check the voltage across the battery terminals, The voltage should be >= 14.4 volts to charge the battery. A voltage of 13.6V is a float charge to keep the battery fully charged but won't significantly charge it. You should also check the voltage at the alternator. Check between the main cable on the alternator and a clean ground point on the engine. If there is a difference between the voltage at the alternator and the battery terminal, then you have a bad battery cable and need to replace it. A bad ground cable and lead to reduced voltage getting to the battery as well.

A number of part stores will check the battery for you if you think this is a problem and some might be able to test the alternator as well.

 

[Seahawk]

Sounds like the battery is not being charged properly or isn't holding a charge. Use a volt meter and check the battery with the cables disconnected. If it is fully charged it should read 12.7 volts, at 75% charge --- 12.4V, 50% charge --- 12.2V, less than 12V then It is discharged.
Then with the battery connected with the engine running check the voltage across the battery terminals, The voltage should be >= 14.4 volts to charge the battery. A voltage of 13.6V is a float charge to keep the battery fully charged but won't significantly charge it. You should also check the voltage at the alternator. Check between the main cable on the alternator and a clean ground point on the engine. If there is a difference between the voltage at the alternator and the battery terminal, then you have a bad battery cable and need to replace it. A bad ground cable and lead to reduced voltage getting to the battery as well.

A number of part stores will check the battery for you if you think this is a problem and some might be able to test the alternator as well.

Thank you for your input. I will follow your leads. I appreciate your willingness to help.