Why does cold engine make noise when ac is turned ...

Its just like the first time you start the car during the day,

It has to warm up.

Al

Nanadee it propably right. A cold engine has to work hard, but when it warms up everything works better. How many miles on the car? If it's new this answer is correct. If it's old, check the AC clutch and the drive belt. Sometimes it sounds like engine noise, but it's the AC clutch.

The basic cause of noise being generated by a cold engine is that parts change size and elasticity during the warm-up phase. Also, internally to the engine lubrication takes a few minutes to reach its potential. The noise associated with A/C system is mostly attributed to drive belt reaching operational temperature, and the internal fluids being circulated within the system, IE, refrigerant and compressor oil. The older the vehicle, and the more miles it acquires, the more noise will be generated.