@gixxerfast I just looked at the wiring diagram. It has this warning:
"Note: These outputs are protected by a flyback diode connected to V_OUT_LC_2. Do not mix loads connected to V_OUT_LC_2 with the jumper set to 12V and loads connected to V_FUSED on the same bank."

@Danal The code did the trick. Homing Z works like a breeze. Thanks.

@phaedrux I think the issue is the board is treating the bed heater like a nozzle heater. It is running tests with the fan on and fan off.

These codes:
M308 S0 P"temp1" Y"thermistor" T100000 B4138
M308 S0 P"temp0" Y"thermistor" T100000 B4138

They look identical. Perhaps there is a code for bed heaters.

@phaedrux Okay, I got things straightened out.

1. That loud tone was coming from my APC battery backup. The printer is now plugged into a surge protector.
2. Bed Heater is now connected to OUT 0.
3. Confirmed bed heater calibration still works.

Thank you very much for the guidance.

It's now a moot point. The replacement fuse didn't resolve. The heater is dead in the water. I am not sure I want to put any more money into my printer.

@gloomyandy Yes, the hazards of using a 20A fuse with a heater that draws more than 20A. Mine draws 16.66A

My heating pad is rated at 24v, 400watts which converts to 17 amps. I think I should be safe with a 20A fuse, correct?

Thanks. I ordered.

I have the Duet 3 6HC. The fuse for my heater bed blew. The board is powered by a 24 power supply. What kind of fuse is that? I read in the documentation that an 18A is rare and I should use a 20A.
Is this the proper replacement:
https://www.amazon.com/40Pcs-Standard-20A-Blade-Motorcycle/dp/B0CS3W7Q94/ref=sr_1_1_sspa?crid=3A2B3BTBE893&dib=eyJ2IjoiMSJ9.yFxFLDVhm7b_hZ7-LeFwdg5gmVmYQhGbqgkgTLFdg-xuX43Z7Usvde42AVZYrxE-GzlgjQDDZP5ZmVUomNsFlAwX7emb9o8vVVn177U00c1bDaAkbwlNZViIfWWIF9z2H7O8I7TWbNneMAFrbHOUwWkVRdMVFwpjhvh9act1O1Qf5-ZjIydI-UVwhvqYD-NU3CSraZt4dMqNWUvZMGBhbFhZ5imJVDMryOjFkdprmdg.mBVX5ofXVr93RLW4OH_tDEXUVvFsC2BW9Wx4rcZ4b6E&dib_tag=se&keywords=20A%2Bblade%2Bfuse&qid=1710940300&sprefix=20a%2Bblade%2Bfuse%2Caps%2C152&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

@dc42 Okay, thanks for clarifying. I wasn't sure which firmware update to use.

What is the difference between 7, 7i, and 7c?

@deckingman Thanks

@dc42 Thanks!

@deckingman I have 2 fans, one for the hotend and one for part cooling. I have decided to just stick with my 24v fans, much simpler.