97 Tahoe Intermittent starting problems

[FFPVON]

I have a 97 Tahoe with a new battery, new starter, and new alternator. It doesn't get driven very often, It will sit for 2 weeks and it'll start up just fine and ill drive it 30 mins up the road to a store or something and when I come back out it will turn over a few times and is dead. It doesn't always do that but 1 out of 5 times. I must get someone to jump the battery before itll start again. Can someone explain to me what could be causing this? I had it looked at by a mechanic and he said it could be from a slow drain in the radio but if that's the case shouldn't it not start from the get go and not after ive driven it?

 

[zora]

have you had the new battery load tested?
what is the battery voltage after sitting two weeks before trying to start it?
What is the alternator output voltage at idle and 2,000 rpm?

 

[Chuzz]

I'd suggest checking all of your grounds. That includes the ground cable on the battery. Check both battery cables for corrosion. Just a little under the insulation can cause all kinds of problems. You need to also look for any broken ground straps from the engine to the chassis. If you live close to an autozone or advance or o'reillys, just take it there and have them load test the system. No charge and they can tell you if it's the battery, alternator or even the starter drawing the battery down.