I have a code 15 we've replaced the coolant sensor and we still have a code 15

What is your question?

Sputters and stumbles then turns off and check engine light comes on but only when ac is turned on

What makes this problem better or worse?

Nothing

How long has your 1992 Chevrolet S10 had this problem?

A few weeks ago replaced the temp sensor and cleared codes and was fine then started cutting off and loading up and turning the check engine light back on