I have E3 showing up on my Conia air conditioner an cannot find the booklet that came with to find out how to fix it ???

Sounds like either bad reversing valve or to get you going during the summer someone may have wired it to stay energized all the time which would have been a thermostat problem.

Not sure if this is what you are looking for. A Make and Model would be a great help in finding the information that you are looking for. So we at West Palm Beach Air Conditioning would love give you a hand.
Manuel:
https://highcongtana.files.wordpress.com/2015/10/conia-air-conditioner-manual-ca24003.pdf

Try this: http://www.manualslib.com/

I Googled this: Fuji air conditioner E3 Error
One item seems to have the answer:
http://errorcodeairconditioning.blogspot.com/2010/10/fujitsu-air-conditioner-error-codes.html
"E3:00 Return air thermistor short circuit"
So more than likely you have a crossed wire issue. good luck.
I'd call ACND service man!

micheline, according to the LG Owner's Manual for the Model Number you listed, there is no LED display on the casement window unit (please see the Owner's Manual link below). How are you getting an E3 error code? Or by chance, did you list the wrong model number? Even Goldstar, that is made by LG, doesn't show your model number.

Please advise. Thanks.

Indoor unit air sensor defective. Replace it. Thanks.

it says on the web site somethin to do with the refrigeration pipe ,mine is doin the same thing hope this helps

E3 FROST PROBE OPEN: Normal operation is allowed. Replace probe.
E3 FROST PRObE OPEN: Normal operation is allowed. Ohm frost probe. Replace probe if ohm value not read. If ohm value is present replace board. 

Thanks. Keep updated for any more query. You can rate this solution and show your appreciation.

NOW, THE EVAPORATOR COILS NEEDS CLEANNING OR THE DRAIN LINE PLUGGED,OR JUST CLEAN THE FILTER.

TOYO mini split air conditioner made in Japan is very very good quality and it can runs for 20 years without any problem. E3 means low pressure of refrigerant. You didn't hire a best ac technician to install your TOYO unit. The tubing connection between indoor unit and outdoor unit is not the right torque and refrigerant leak. Your TOYO unit runs out of refrigerant. You need fix the leak and fully charge the system. You will solve the problem. Good luck to you!