220A Alternator idle output voltage and amp.

[Laurent Kim]

Hello all!

Does anyone have any idea what the idle output voltage and amp capacity of 220amp alternator on 2020 GMC Sierra 2500HD?

Thank you,

 

Laurent

[SilveradoX2]

Start the truck and look at the voltmeter.  If it is about 12 - 12.5, that is the battery voltage.  The alternator is not putting out enough to carry the electrical load, especially if the AC is running.  Bring the RPM up to 750 and observe again.  If the voltage starts to climb toward 14 volts then the alternator is generating enough to carry the load and charge the battery.  My experience by 1250-1500 RPM the alternator is at maximum output.

[redwngr]

Alternator is managed by the computer. 

 

Many items affect the output that the computer commands the alternator to put out.

Pages of info about this in the outfitter docs.

 

Definitely not like the 'good old days'.

 

 

[newdude]

On 10/5/2022 at 10:34 PM, Laurent Kim said:

Hello all!

Does anyone have any idea what the idle output voltage and amp capacity of 220amp alternator on 2020 GMC Sierra 2500HD?

Thank you,

 

Laurent

 

 

Whatever the ECM and BCM tell it to do.  The charging system is entirely computer controlled.  It can alter the duty cycle of the generator based on if you are highway cruising, running high demand loads (plow, lots of lights, trailer charging) etc.