You do not seem to be missing anything. Sorry to say, you may just have a bad audio circuit in the unit. You can try resetting it. If it has a reset button press it and see if that helps. If you have no reset button, disconnect power for a few minutes and then reconnect it and see if that helps.
You seem to have the settings right so other than a reset there is not much you can do with it but take it to a service center that works on them. It may be hard to find one locally, parts and service data are not readily available for Garmin products. Here is the information you would need to get in touch with Garmin.
Website url:
http://www8.garmin.com/support/warranty.html
Other information:
STEP 1: Contact Garmin Technical Support to receive an RMA number.
Call or e-mail Garmin Technical Support Specialists to describe the problem you are experiencing and request a Return Material Authorization (RMA) tracking number. You will need to provide the unit's serial number (if applicable), your return shipping address, and a daytime telephone number.
***Aviation Panel Mount or Aviation Remote Mount products require an authorized person to return the aircraft system to service after product repair. Please arrange RMA's through your favorite Authorized Garmin Aviation Service Center.***
Phone:
1-800-800-1020
913-397-8200
Fax:
913-397-8282
For Garmin AT products only:
Phone:
1-800-525-6726 (U.S.)
1-800-654-3415 (Canada)
503-391-3411
Fax:
503-364-2138
STEP 2: Ship the unit, along with the RMA number, to Garmin.
Once you have received the RMA number, securely package the unit and ship it (insured) to the following address:
Garmin International
1200 E. 151st Street
RMA Number: (insert your RMA number here - see above)
Dock Door #18
Olathe, KS 66062 USA
For Garmin AT products only:
Garmin AT, Inc.
RMA Number: (insert your RMA number here - see above)
2345 Turner Rd. SE
Salem, OR 97302
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