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I'm going with this dryer being model nubmer MDE9700 or MDG9700
The error code is an indication for "Door Open".
This what the repair manual tells you to check-
Check for: - Close the door, and run the dryer
- Loose or open wire terminals in Door Senser circuit.
- Check for diagnostic code 3
Let me know if you would like more information.
I've uploaded the repair manual for you to review. It will give you lots of details to troubleshoot and to disassemble correctly. Page 12 explains about the diagnostic codes.
When you go to the site to download do not use AOL. Use Internet Explorer or another browser because that site does not like AOL. Choose the "Free" option. After you download the file you will need to open it with Adobe or another application. You should already have that on your computer.
Sometimes, the site is a little glitchy. If you have difficulty, clean your temporary files and your hard drive, restart the computer and try again. It's definitely worth it to have the right information. You can go to the top left corner (after you open it) and save the PDF file to your desktop for easy access.
Please click here - Dryer
Please click here for a updated tech sheet for removing the console - Tech sheet
Please let me know if you would like more information.