I have an LG dryer model #DLG5988W that has no heat and has all filters cleaned. What is the most common cause of this problem?

There are a few reasons that the heat will quit. It could be the element that looks like a coil or spring pulled out loose and it is what heats up and quite often if the dryer is older the element breaks and needs to be replaced. Before you take anything apart though go to your breaker and look for the dryer breaker. It is usually bigger than the rest as it is on a 220 volts and if only one of the breakers is tripped the dryer will run but won't heat up it needs that extra 110 volt breaker flipp;ed on to heat the element.There is also a sensor that may have gone on the blink but unless you are real handy with a volt meter and a screwdriver set you may haver to call the pro's. If you do want to fix it your self you will need to get to the inside and get the drum out of the way so you can get access to the element.if the element is the cause it will be broken at some point in the coils and will not be attached 100% all the way around so it is unable to complete the ciccuit therefor not turning on and heating up.If you want to do this you self I would write back asking for step by step instructions to do this.If this has helped you dont for get to click yes on your way out thanks again and good luck!