Dlg5988s dryer does not dry clothes

possible blockage in vent if ok bad fan motor or heating element overheating

GOD IS STILL GOOD !!!!

ELECTRIC Dryer no heat or little heat, or shuts down to fast:

Check your venting and lint basket. Check blower for lint build up and blower wheel obstruction., test by trying to turn the wheel manually by hand (should be easy) May have to remove cabinet or front/back plate to get to it)

Next check the heating element itself with a meter for continuity OHMS CLOSED CIRCUIT. If not its defective or has a short if its grounding out? Which in turns causes blown fuses or thermostats or overheating.

Check dryer Terminal block prongs both outside prongs should give combined 220, and 110 each if u check 1 outside & 1 center (ground) prong. Also check house electrical outlet for full voltage. 220 because if u only get half or 110 volts you will be able to run the machine which uses only 110 to run motor but not the heater which uses a full 220,

Check the thermal cut off, the cycling and the hi limit thermostats.
For continuity or OHMS. If no ohms or resistance they need replacement.

In some dryer's the control panel relies on a thermistor rather than a CYCLING thermostat to regulate the drum's air temperature by monitoring the component's resistance changes; resistance goes down as temperature increases and up when temperature decreases. Once the drum's air temperature reaches a certain level required to dry clothes, the control panel shuts off the heater. The panel will turn the heater on again and begin another heating cycle when the thermistor indicates that more heat is needed to keep the air temperature constant inside the drum

Lastly check your moister sensor. ( located inside the dryer door usually) Especially if machine seems to shut down early and clothes are still wet.
Test with a meter at room temperature and it should show continuity.
A failed moisture sensor will affect the dryer run time in the automatic moisture sensing cycle but it will not affect the heating of the dryer or the timed cycle. Which are reflected by the thermostats.

Read more :http://www.ehow.com/info_12203962_check-dryer-thermistor.html

Inside the dryer, near the lint filter, you will find two curved metal bars, about 1/4 inch wide each, about an inch apart and about 4 inches long. These sense the moisture in the clothes. When fabric softener sheets are used, a waxy substance will eventually coat the bars, so the dryer will not "see" that the clothes are still wet, and go right to a cool down. Clean them off, or use time dry only.

It seems to run forever If your dryer seems to run forever, it could be because of a clogged vent or internal ductwork. Your dryer may have an automatic cycle that turns off the dryer when the clothes are dry. It does this with a special thermostat or moisture-sensing system. Normally, this is what happens during an automatic cycle: The thermostat tells the dryer to heat until the interior of the dryer reaches a pre-set temperature--say 135 degrees. When the dryer reaches the pre-set temperature, the thermostat tells the timer to begin advancing. (If there's a moisture sensor, the timer advances only if the moisture content of the clothing is low enough.) The timer advances until the interior cools, then the thermostat tells the timer to stop advancing, and tells the dryer to start heating again. This cycle continues until the clothes are dry. But…if the vent is clogged, the dryer may never reach the proper operating temperature, so it doesn't send the signal to the timer and the dryer continues to run indefinitely, even if the clothes are completely dry. To fix the problem, clean the vent and/or internal ductwork.

there are two elements on the back wall of the dryer and if one goes it will still get warm but not to dry all the way and will not trigger the heat sensor to finish

Based on your issue description, Gas and electric dryers have heat sources that are controlled by a cycling thermostat. This thermostat will cycle the heat on and off numerous times throughout the drying cycle. It should never keep the heat on constantly as this would cause clothes shrinkage and a chance fot a lint fire. If the dryer is drying clothes normally then you have no problem.

call svc tech under warrenty, also sensor rellies on clothes touching two shiny strips to sense the dryness of the clothes ussaly in front or rear of drier drum or rather back or front wall inside wet clothes short the bars and stalls timer when they are dry does not short bars so sensor knows dryness by resistance of short tilt drier front or back where ever bars are to make shure clothes main tain contact lots of time this cures the promblem

The vent is clogged.  To make sure, disconnect the vent from the dryer and run the dryer normally.  If your clothes dry normally, then have a professional vent cleaning company take care of the vent.  
The cooling light will always stay on during the run.  When it is blinking, the heat has stopped and is in the cooling process.
If there is no heating, you have a problem with the high limit switch or something else electrical and needs to be addressed by a qualified LG technician.