DTS...she no starts

I need some help. A family member a few states away is having an intermittent start issue with his '06 Caddy DTS. Sometimes the car starts fine. Sometimes he gets all of the dash and interior lights but no starter, just a click. This can happen overnight, or, it can happen after a week of no problems. The dealer (car is still under certified used warranty) has checked the battery a couple of times and says it is fine. They won't replace it beacuse they will not get re-imbursed from GM unless the battery fails the output test. The service records show that the battery was replaced when the car was one year old (when owned by the original owner). Hmm? Could this be a lingering problem? The battery is located under the back seat. Is sounds like the ground going from the battery to the chassis contacts a painted surface?! Any chance that if my family member replaces the battery, removes the paint under the ground contact, re-attaches the ground and applies some di-electric grease that the problem will be solved?

In reply to racer_ace:

Your problem isn't the battery if it tests fine, I'm guessing something isn't fully disengaging after shut down, alternatively it could be the alternator, has he had it checked? My 98 Eldorado had a problem with the ignition switch not fully disengaging, but the shift select switch on the dash would remain illuminated so I learned to make sure it went off. I also gobbled alternators like no ones business. On my year though I could alter the checksums in the driver information center to display voltage, was easy to follow the death of my alternators after that. The FWD N* has a nasty habit of killing alternators because they placed them next to the front exhaust header behind the radiator, so they get heat soaked. Caddy played around trying to liquid cool them and whatnot but eventually just gave up. I'd start with an alternator test, then have the dealer diagnose open or shorted circuits when the car is off, tell them they have to fix it, you paid for the service, they need to figure it out...

Just a guess... but my Dakota had those symptoms and it turned out to be the actual battery cables.

Just a click could be the starter solenoid not making contact.

Thanks for all of the suggestions. The reason my uncle is thinking that it is the battery is beacuse if you jump it the car starts right up. In addition, he has been using a battery tender at night and it has been taking longer and longer for the battery to fully charge. Although this symptom could be due to a progressively dying alternator as Raze suggested (i.e. the battery is being "drained" more because the alternator is not functioning properly).

I have been working at a Cadillac dealer for years. I doubt it is the alt. In most cases they have a draw on the battery. Also the Delco battery in this vehicle are known problems after a few years, sounds like it was replaced in 07. The "tester" used in GM dealers for warr claims is not able to put a high enough load on the battery to test IMO. Charge the battery & test for a draw, around 40 miliamp draw is normal for your model car. Check it overnight if you have a dvom the will record min & max amps. Let me kow if you need any other help.

my 2 ¢ worth... if the dash lights are there but no start, just a click, and a jump start takes care of the problem, then it seems (from this far away) that the bat isn't fully charged....

like todd900ss said test for a draw....