Whenever my defroster or ac is on you can here something like a little motor kick on and off, is this normal

 

A/C compressor maybe?

 

Is it normal for It to turn on and off every 20 sec or so

 

Could be low on refrigerant, ours doesn't cycle that frequent.

 

How long is it before yours cycles

 

Depends on ambient temp.....cool/cold weather using defrost, it cycles off for just a few seconds, then back on for several minutes. Warm/hot weather, it seldom cycles off. Our a/c system is almost new, replaced last June.

 

Sweet!!! Thanks for the info bro