For the past few months my wifes tahoe sometimes will not start. About once every 2 weeks or so she will get in it to start it up and it will not start, will not even try to start so we have to jump it off. It will be good for a week or so and do it again. Today it did it 3 different times so I though maybe now we will be able to find the cause, maybe bad battery or alternator. She took it to Auto Zone to test the battery and alternator and all checked good. Battery cables are tight and clean at the connection. Very strange problem. Any suggestions would be appreciated.