tone noise under dash HELP!!!

[foulbeast]

got an 01 F350 w/7.3. the last two times i started the truck a tone noise starts coming from under the parking brake pedal area. when the truck is running the noise starts about 5-6 seconds after it is started. there are no warning lights on the dash (unless they are burned out). when i turn the truck off and take the key out the noise is still on. the only thing that turns it off is disconnecting the batteries. i just bought the truck and and dont know alot about it but i am mechanically inclined. tried putting on my seatbelt and made sure the doors are closed and made sure it wasnt those. any help would be appreciated.

Thanks, foulbeast

[Turbostang500]

Check the battery voltage. Seemed to me there is a buzz noise under the dash when bat voltage is low.
To have the bats tested, they need to be unhooked from the truck. Since there is 2 bats, they will pass if testing like it is one bat. Just unhook one, then both can be tested.

[foulbeast]

ok thanks i will check in the morning and let you know