Why does my defrost turn on the AC light? Is that normal?

It’s getting cold now, and I’ve noticed that every time I set my truck to defrost, the AC light switches on. I drive a 2000 Tacoma with a 2.4L engine. Someone at an auto parts store told me it’s meant to do that because the AC removes moisture, but I’m not sure if that’s the whole story. I’ve also read something about relays being involved. Has anyone else experienced this?

The guy at the auto parts store was actually right this time. It’s supposed to work like that.

Josie said:
The guy at the auto parts store was actually right this time. It’s supposed to work like that.

Haha, if he didn’t try to sell you some random stuff like wiper blades while saying that, he’s definitely a rare one among auto parts guys.

Yep, that’s how it works. The defroster uses the AC to clear up moisture from the windshield and keep it from fogging up.

I’ve heard it also helps keep the AC system in good shape by cycling the refrigerant, which has oil in it. The oil helps keep the O-rings conditioned so they don’t dry out and start leaking. Can someone confirm if that’s still accurate or outdated info?