A/C surges and Battery light on?

[Texan6Seven]

I noticed the battery light come on a few days ago and then go of a few minutes later. Over the last couple days everything has been normal. Then today I noticed the battery light came on every 2-3 minutes but now the A/C surges when the light is on. WTF?! I checked both batteries and the cables are tight at the posts. Has anyone had this happen to them? I drive a '13 250 fully loaded with 60k on the clock.

 

[CATDiezel]

Batteries are more than likely bad. They need load tested. Could be an alternator issue as well. Generally a 10 cent diode in the regulator that fails and causes no regulation or wide open regulations. The ac was surging because it lost amperage to the relay coil to hold the clutch against the compressor. And the blower motor would slow down with the dc voltage curving.