Ok I just got my f150 (2002 4.2 2wd) a couple of months ago. It has a 2 year old battery.. and my brother-in-law replaced just about everything else that could be potential issues... It sat for a few weeks as I never had time to get the registration done. It had a check engine light and I knew it was a lean issue.. I cleaned out the MAF as a first check.. in doing that I unplugged the battery for a day or two to let it all reset. Of course when I plugged it back in, and I got clicking.. the truck had to be jumped... started and was fine started up fine the next couple of times I moved it just in the driveway.. no long term driving basically on then off to move it to clean or paint something. Left it for a week and it needed to be jumped again (clicking again).. started right up I drove it for the day to work then the next day I drove about 40+ miles around town.. parked it for a 5 days... yesterday I started it right up drove it to end of driveway to drop some trash and things on the curb for trash pickup.. started right back up.. went to work (5 miles away) after work started right up.. drove a mile to drop of clothes at Goodwill.. started right up.. drove to my in-laws (live just down the street from me) stopped.. started right up.. drove to my house backed in driveway and got out to take my car to store for about 40 minutes.. when I got back turn key and there was nothing no lights no clicking.. nothing. I was going to try to jump it and when I put the jumper cables on my truck battery only.. the hood light came right on.. went to start it after I saw that nothing I cant remember if any clicking... anyway I tried to jump it off my car... would not start.. for the about 1 minute I tried.. then I got dumped on from a storm. I came back later and all lights work when you open the doors.. wouldn't start this morning..

What do you guys think? bad battery? could it possibly be a bad connection.. I know I can slip the battery cable connectors on and off and it did not even occur to me until I wrote this that maybe the reason all the light came back on when I put the cables on was the connection was made.

but they looked to be on..

 

Change out your connectors and clean the battery post, cable, and even new connectors well. I bet you'll fix it with that.

 

1. Clean/tighten your connectors
2. Make sure cells are filled properly
3. Check specific gravity /charge level of cells
4. If not charged, charge it completely .
5 see if problems reoccur

Cheap batteries are good for about two years. Then they often suddenly lose a cell.

 

Neutralize the Acid on the Battery Terminal & Cable Terminal using baking soda and water. Apply some Electric Contact Grease on the terminal to prevent corrosion.

 

Take a test light or digital meter and pull battery cable. Put the tester (which ever you use) between the post and the cable end and see if the light comes on or the amount of voltage you have running thru your meter. This will tell you if you have a draw on the system and if you do, then start eliminating the fuses until you find your circuit that is taking all the power, if that's what the test tells you. Then fix the that circuit. Make sure the battery is 100% charged before testing. It keeps from giving you a wrong number. And do like was said, clean the connections at the battery and the battery posts. Make sure you get a good connection all around.

 

clean your battery terminals and make sure they are tight.

then find the other end of the battery cables and make sure those ends are rust and corrosion free and tight

 

A voltmeter will tell you a lot about the electrical system.
What is the battery voltage after it sits and won't start?
The system voltage should be 12.3-12.5v just before starting.
It will barely start if the voltage is around 11.8v.
It will drop to around 10v when cranking.
When the engine is idling the volts should be 13.3-13.8v indicating the alternator is outputting and charging the battery.
If the volts are 10-10.5v just before starting there is a dead cell.
There will be a constant draw on the battery when the engine is off because there is a receiver looking for signals from the key fob remote door lock transmitter, but the current draw is minimal. There will be a tiny spark if you tap the battery lead to the post. A large spark indicates something else is still on and needs to be found - hood light, glove box light, etc.