I have been using a deep well pumping system for over ten years. I recently replaced my cut of switch. According to the pressure gauge the switch is set to 20/40. It use to take a minute or two for it to build up enough pressure to click off.Now, the pump appears to cut in too often. It builds up the pressure with in a few seconds. I am still getting plenty of water but when water is being used it cuts in and out continually.
Any suggestions.

Hi! FiggyDuff, and Welcome to AMHD :)

How's the weather? Are you in a dry or drought condition?
Had that happen to us once during a drought, pump was suckin' bottom.
Your aquifer could have changed.
Loss of air pressure in air bladder.

Did it do it right after the swap?

Check this link, part way down on the left is TS and diagnostic links.

"KUDOS" to jlisenbe for the link.
How to adjust water pump pressure, pump cut-on pressure and pump cut-off pressure - private pump and well system do-it-yourself repairs

This one, same site, on:
What Causes "Water Pump Short Cycling" - a water pump turning on and off too rapidly - How to diagnose water pump short cycling and how to restore lost air in a building water pressure tank - private pump and well system do-it-yourself repairs

K

You probably have a ruptured bladder in your pressure tank, a rather common problem. You can check this by holding down the little air valve at the top of the tank for a few seconds. If water comes out, then the bladder is ruptured and the tank needs to be replaced. For the short term, you can turn off the system at the breaker, drain the tank from a nearby faucet, pressurize the tank with an air compressor to 20# or so, then turn the system back on. But that will only last for a few weeks. Replacing the tank is the only long-term solution.