Put a wrench on the fixture or nut and strike the handle sharply with a hammer to loosen the fixture.
Delta sink faucet bonnet nut stuck.
If the fixture or nut hasn t loosened go to step 2.
The bonnet nut fits over the faucet valve and holds the valve into place.
To remove the bonnet nut turn it in a counterclockwise direction with a wrench until the nut is free from the threads on the valve then lift the nut up and over the valve to complete the removal process.
To remove a stuck faucet nut you need a wrench or locking pliers to break the mineral deposits grip and then turn in the opposite direction.
Make sure that the surrounding area is free of any valuable items as the action to strike the motion against the plumbing nut.
Here are some nut freeing tricks from richard trethewey.
Removing a stuck on bonnet nut when changing a cartridge on the delta shower valve.
Apply heat to the stuck fixture or.
The easy way to access a corroded basin faucet fixing nut for removal.
Sometimes you need a hammer to break the nut.
Remove the faucet s bonnet nut.