Lights are pulsating(voltage prob?)

Have a 2001 Jimmy SLT. Headlights and dash lights pulsate as soon and you start driving. Didn't notice it in park. Wifes car and I haven't had time to look into it. Any ideas?

Have a 2001 Jimmy SLT. Headlights and dash lights pulsate as soon and you start driving. Didn't notice it in park. Wifes car and I haven't had time to look into it. Any ideas?

I would get the alternator output amps and charging voltage tested.
Also test battery and connections.
Check the back of alternator for good wiring and wiring plug in.

I had A 91 s-10 blazer 4.3 liter that did that it was the ground wire at the thermostate was coming loose.