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Parts for Whirlpool WED4800XQ0 Dryer - AppliancePartsPros.com

See the attachment for the tech sheet.

[COLOR="Blue"]It does heat on the "automatic dry" side of the dial, but does not shut off when dry.[/COLOR]
Does the timer advance or just stay where it is set?

Set the timer to timed dry where it does not heat.
Then unplug the unit.
Check the A to B contacts on the timer, should be 0 ohms.
Note that it is a good idea to disconnect the wires from one side. This ensures that you do not read an alternate/parallel circuit path.
Also use the most sensitive meter scale, usually 200 ohms.

The problem may be the contacts in the timer.

Th heater circuit is the same in both timed and auto so that is why I suspect the contacts are not closing during the auto (a different place on the timer cam).

As far as timer advancing.

In timed dry the timer motor gets power through Timer Switch 0 (T to X).
X is connected directly to L2. T connected to one side of the timer motor withthe other side of the motor connected directly to L1.

In auto the timer motor gets power through Timer Switch 0 (T to F). Also it only gets power when the heater shuts off.

I would use a meter and check it first.

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.
4. When you start always short the meter leads together. This will tell you that the meter is working and if there is any 0 offset.

There is a good STICKY at the start of this forum about it's use.

Yes you need a new timer