Seller promised to fix heat in car before "AS IS" was signed. Seller never fixed heat in car. I got heat fixed and seller refused to reimburse me.
Yes, you bought the car "as is", not as promised.
There was nothing in writing to PROVE what you say the person said.
If it isn't reduced to writing, it never happened, or it wasn't agreed upon.
Either way, the seller never agreed to fix the heater in writing.
The seller sold you an "as is" piece of cold JUNK, and you bought it.
You got what you bargained and paid for, an "as is" bucket of bolts.
Enjoy it, as you fixed YOUR bucket of bolts.
The seller owes you nothing.
If you believe otherwise, off to small claims you go, only to hear a judge tell you, after you spend more good money chasing bad, CASE DISMISSED, verdict for the defendant.