Sometimes battery connections get corroded and just barely make contact. Check the hot and ground cables. Scrape the connections clean, and apply some protective grease to prevent more corrosion.
It would best to get someone who knows something about auto electrics to check the connections out with a voltmeter, though. Then you can be sure you've found the problem.
Why does my Jeep intermitently not allow me to start my car? I get serious relay clicking at left foot of driver side. I have tried waiting a few minutes, I have tried using the keyless remote..nothing seems to work other than wait. It appears as though I have a dead battery..but its not dead. My lights dimm, my electric locks dont work,the cluster is barely lit..its totally spooky. Some times my clock resets to 12 and yet the stations are still programed!! Someone said it may a security issue...but how do i tell, when the car has this problem I cant use the remote to unlock or anything..I did disconnect the battery for 60 seconds and reconnect it...which did work..FINALLY, just not sure how long before I see another "can't start" senario. Any help?

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