If you replace your alternator and engine is revving up and down at idle...

I just found out that you need to reset the idle.

To do this:

After engine warms up, turn it off. Turn to on position without cranking the engine, and turn off. Do it one more time.
Then turn your engine on, activate your E-brake and put it in Drive.
Once the fluctuation stops, you have reset your idle.

Done!

 

Then do the Hokey Pokey and you turn yourself around………

 

You missed "spit three times" after "activate e-brake".