If your dryer is either not getting hot enough or if your dryer is getting way too hot and then shutting off, here are a few things you can do to troubleshoot what is wrong with your dryer.
#1 Pull Your Dryer Back From The Wall
Overtime, your dryer could have gotten pushed back from its original position. If your dryer has gotten pushed back too far, the air duct hose that provides your dryer with the air that it needs to effectively dry your clothing may be pinched. If it is pinched enough air will not be able to get through and your machine will not be able to work properly. The moisture may also not be able to escape, leading to a build up of heat.
#2 Check The Exit Of Your Air Duct Vents
Your air duct vents should excel air to the outside of your house. However, it is easy for these vents to get clogged up or covered up. Go to the outside of your house and pull out any debris that has gotten inside of your vent. Make sure that no plants are growing too close to the vent and blocking the airway; if they are, trim them back. Also, make sure that no items are being stores or leaned up against the vent and preventing it from properly venting
#3 Remove The Air Ducts
If the two steps above do not work, you are going to want to remove the air ducts from the back of your dryer. Pull your dryer out. You are going to have to remove either screws or claims that are holding your air duct in place. You should turn off your dryer before you remove the air ducts. Once you remove the air ducts, you are going to want to clean them out. Oftentimes, the air ducts can get clogged with lint. You are going to want to purchase a long brush that you can spin to remove the lint. Be careful that you don't damage the vent; gently twirl the brush but don't poke around with the brush.
If this doesn't work, you are going to want to hire a dryer and washer repair service to come out and service your dryer for you. They can clean further down your air vent. They can also take apart your dryer and remove any internal clogs that is negatively effecting the heating in your dryer.