Just after start up the volt meter jumps back and forth from 15 V down to 12 v, for a few minutes then stays in the 15 v vicinity. What does this indicate? Faulty regulator, alternator, or is it normal. Truck is an ’06.

 

that in certain cold start situations it is normal for the voltmeter to fluctuate, the headlamps/interior lights to dim and/or the heater blower to slow down/fluctuate for approximately 3 minutes or if driving under approximately 18 MPH. This is due to the high power draw of the intake grid heaters and is not representative of a problem with the electrical system. Replacement of the alternator will not correct this normal characteristic. Please refer the customer to the "Starting and Operating" section of their owners manual where these normal operating characteristics are described in detail.