Samsung DV218 AEW works fine in time dry but not in normal dry. Jumps from 50 min to 1 and shuts off.

Check your vent who much air go out, your vent is 4 inch or small , need 4 inch vent with flapper open

If it is on sensor dry it will do that. try putting it on timed dry.

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19.
Be sure to show your work.

If you don't have clothes in it, the units moisture sensors will automatically end the cycle if you're on anything other than timed dry.

clean the stainless steel sensor pads located just inside the dryer door with isopropyl alcohol,these sensors register moisture in the garments and adjust drying times accordingly,when you use dryer fabric softener sheets it coats these sensors and throws the system off,make sure to shut off power to unit as this alcohol is very flammable,then leave door open to air out before re-powering up unit

venting issue, here is a website that will be helpful, Good Luck Tim:

http://www.applianceaid.com/general.html#timers

I'll take a stab that you use dryer softener sheets. These will deposit a coating on the two metal sensor bars (about 4 inches long, very near the lint filter inside the drum) which prevents the sensor from "seeing" that the clothes are still wet, so the dryer jumps to the cool down portion of the cycle. Clean the metal bars off and it should work again. (note: the bars are not in the cycle if you choose time dry instead of using the automatic cycles)

Clean off the moisture sensor bars. They are the silver curved strips about 4 inches long inside the drum near the lint fitler. If you use fabric softner sheets, a waxy build up will coat the bars. The dyer can no longer sense the damp clothes, so it goes into the cool down and then shuts off. Time dry bypasses the moisture sensor.

hi Step 1: To access the timer, remove the front of the control panel. On some dryers, the timer can be removed without removing the panel. In either case, pull the timer knob off the shaft and slip off the pointer. The pointer is usually keyed to the shaft by two flat surfaces to keep the pointer from slipping when it's turned.
Step 2: Test the timer with a VOM set to the RX1 scale. Turn the timer to the NORMAL DRY setting and disconnect one of the timer power leads. Some timers may have several wires connected to them: The power leads are usually larger than the other wires, and this size difference can be spotted under close examination. Clip one probe of the meter to each timer terminal. If the meter reads zero, the timer is working. If the needle jumps to a high reading, the timer is faulty and should be replaced. Replace the timer with a new one of the same size and type.
Step 3: To replace the timer, have a helper hold the new timer close to the old one, especially if there are several wires to be changed. Disconnect the old wires one at a time, connecting each corresponding new wire as you work, to make sure the connections are properly made. Or, draw a diagram detailing the proper connections. After all the wires are connected, check the connections again for accuracy.

the glow plug sensor not accurate send to timer /replace sensor