When I turn my headlights on the motor loses power and the cruise control stops working?

It sounds like the alternator is weak on recharging the system but to be sure here is a guide to help and I have included how to change the alternator out in the images below.

https://www.2carpros.com/articles/how-to-check-a-car-alternator


Check out the images (below). Please let us know if you need anything else to get the problem fixed.

Thank you for your reply. The alternator has already been checked and it is good.

With the engine running and the headlights on, let's check the voltage at the battery. Here is a guide that will help, the voltage should be about 13.5 volts:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go over this guide and get back to us.