Charging systems

[pbabin]

At one time, I read that in some GM trucks, the alternator would be completely switched off until the battery voltage dropped to a preset level. This was supposed to increase fuel efficiency. Was this something that ever became reality? Or have the continued to use  the old style charging system where the alternator produced a constant voltage?

 

Thanks in advance.

[dsr611]

Yes, they are set up so that the alternator only charges when the voltage drops and calls to be charged.  Voltage, according to voltage meter in the instrument panel, will fluctuate between about 10v and 14v.

[Supreme Pizza]

Huh. Interesting. 

[dsr611]

This is from the 2007 owner's manual.  It doesn't necessarily "switch" the alternator off, but voltage will fluctuate