Mother-in-law called and said she had no water.
The well pump is 1hp 240V single phase. Pressure switch and foot valve new in July.
Power into the pressure switch is good but coming out, one leg is not there.
Contact points on one side look black and pitted.
Gave it a tap and it started to work. Let it cycle several times and all ok.

The bad contact side makes a big spark when opening, not so on other contacts. Is this normal?
Is this just a bad contact or is something causing the big spark?

Sounds like an eroded contact. It would be unusual for it to go that quickly. What brand is it?

Square D.

That is what I am trying to figure out.
Is there something else causing the big spark or just bad luck to get a bad contact.

I totally spaced about checking the amps. I should have done that.

Ok, crappy switches I would expect this but not square D unless it was just a bad one. Check pump amps and replace switch. If it happens again it seems likely to be pump pulling too many amps.

do you have a well controller? it's a device tokeep your pumpfrom burning up or getting too hot if the well goes dry.

Replace the pressure Switch.
Make sure your expansion tank bladder is not ruptured and / or water logged. This causes excessive cycling.   There's usually a Schrader valve to check /add air. If you depress the Schrader and water comes out usually the bladder is busted. Replace the tank.

Bad contact..........SOME are replaceable.

I've seen this once on my pressure switch also a square d. A wasp had gotten between one of the contacts just barely letting it close. The arc was enough to ruin the contact.

make sure when the switch closes, the contacts are even, you should see a bar with 2 contacts on each side of the pressure switch. if one is tweaked or not square, it can cause premature wear.
check your amps when it turns on and when its running. you could be drawing high amps during start which can cause premature wear. usually caused by voltage drop, (at the switch, wire nut in the well loose breaker etc) or even a motor that is starting to go bad. but thats the worst case scenario and i wouldnt jump to that conclusion.
i bet its not mating square, bent or tweaked spring or whatever.

turn off the power, verify its dead, and clean them up and run it.  use a file or sand paper to just clean them up/take of little material off, press it closed by hand and see if there is high spots etc, make it mate square and even, you dont need to take alot off, its silver, so itll file easy and fast.  just a c hair can make the difference.

Is the pressure switch actually rated for 1 HP @ 240V?

If not, it won't last long.

They are about $20 to buy a new one. Replace it.