I just need heat for the defroster.

I didn’t have have heat in my car for years. Yes I live in Texas not much need for it but when I went up north or to the Gulf Coast states I soon discovered how important a defroster was. I started using RainX Defroster on the front and rear glass in my Barracuda. It’s a lot of real estate to cover and worked great. I would apply it about once a month. Drove it for years like that.