My Tahoe won't start

[Bos1girl]

Saturday I tried starting my Tahoe when I turned the key I got only a click. No power to the radio , no lights, no gauges no nothing. Had a friend jump start it and went and bought a new battery, the vehicle started fine until this morning when it was back to just the click and no power now we can't even get it to jump start, it tries to start but it acts like there is not enough power. Could it be the alternator or the starter? Maybe a bad battery?

[Bos1girl]

Update to my previous post. I have recently went out and checked my Tahoe I turned the key but not far enough to bump the ignition . There is no power. The gauges do not move , the lights do not come on , the radio does not work even the beep that you hear when the door is open does not work.

[PhilBy]

Something is sucking the power out of the battery ............ silly question but you didn't leave the lights on??

[Bos1girl]

No the lights were off and nothing was plugged into the cigarette lighter. It started fine last night and this morning nothing. Now our temps dropped overnight from 45 to 15 degrees. However with a brand new battery I would expect it to start. Would a bad alternator drain the battery like this?

[SeaJayPea]

An alternator wouldn't cause the battery to drain. It's more likely that something is constantly on. For instance, the light in the boot. Sometimes these switches stick and don't turn off. Or the rear screen heater.

I'm assuming there were no red lights on on your dashboard when it was running.

[Hymie]

To find out if your battery is being drained, and to determine which circuit/item is drawing the current � remove the negative terminal from the battery and connect an ammeter between the battery negative terminal and the vehicle chassis (the meter + lead to the chassis and the meter � lead to the negative battery terminal).

Ensure all vehicle electrics are off, including any courtesy lights. The meter will be reading the continuous drain on the battery which should be less than 0.2 Amps, even with an alarm system attached. (If your battery is draining overnight, the drain current must be at least 4 Amps).

Assuming your battery drain current is significantly greater than 0.2 Amps, pull the fuses one at a time until the current drops, identify the faulty circuit. Bear in mind that some circuits pass through more than one fuse.

Once you know the circuit with the excessive drain � disconnect individual components until the battery drain current is less then 0.2 Amps.

If the vehicle will start, it would be worth checking that the alternator is charging the battery; at rest the battery voltage should be around 12V. With the engine running, this should increase to just below 14V.

Although the purpose of the alternator is to charge the battery, it is possible for it to be the cause of the battery drain, due to a faulty diode.