Is a 2002 Ford Explorer XLS worth spending $1500 in repairs or should I just buy a new car?

Bought it new for $18000 At 40k miles (1 month after Warranty was gone and Ford wouldn't help) the transmission broke and cost $3000 to repair. Also spend $1700 same year to fix the AC. It kept breaking before warranty was up and Ford kept stringing me along until the Warranty was up. They'd do temp repairs, refill the Freon and say it was something else. After warranty they said it was the compressor. I don't trust them nor this car. But it's long since paid for and don't like taking on new debt. What would you do?

Look up the definition of "sunk cost"

Fix it. You have a low mileage Explorer with a rebuilt transmission. You need to drive for a few years to get your money out of it. You'll lose too much if you sell it.