Question: how to know when you need to change your vape coil?
Answer: A burning taste. Vaping a dead coil will eventually result in an acrid, burning taste. ... 
Gurgling sounds. Vapes shouldn't gurgle. ... 
Weak or “off” e-Juice flavor. This often precedes a burnt taste. ... 
Low vapor production. The vapor produced by your coil will gradually lessen with time.