Battery light is ON only on first start

[darkmaxx1]

Hello,

My car is being weird recently.
When I start it, the first time, the battery light is ON. (cold mornings)

I turn it off, then I restart it. the battery light is gone

What would make the light of the battery turn on only in cold mornings and at the car's first start on the day.

[wagonman76]

Maybe the voltage regulator in the alternator going screwy?

My old Cavalier had a similar problem. Sometimes when starting the volts light would be on and it wouldn't charge. The mechanic showed me how to jump 2 wires at the alternator to give it a kick in the pants and get it to charge. It became so common that I wired a switch up to the dash so I didn't have to pop the hood every morning.

[NiHaoMike]

Might be a bad relay.

[darkmaxx1]

It is the alternator. When the battery light is on, it charges 11.3v and then when we restart again, it is 14v.

[NiHaoMike]

Looks like an intermittent fault in the voltage regulator circuit. Pull the board and post a picture of both sides for more troubleshooting.

[darkmaxx1]

I didn't mention, but I've replaced the alternator on July 2009, and it is on warranty. (except labor XD)
They will replace it next Friday (13 october)

[NiHaoMike]

In many power supply circuits, a common cause of intermittent failure to start up is a bad controller Vcc supply capacitor or resistor. If the resistor increases in value or the capacitor becomes leaky, the Vcc never gets high enough for the controller to start.