newbie used 2X4 method to start pump, need help on which contacts need cleaning.

[kwong]

I think that was like literally taking a piece of 2x4 (wood) and whacking the side of the pump just enough to nudge the components to cause the 'whirring' sound to click in the motor and turn over ... crazy me .. i was desparate and tried it out .. thankfully one knock was enough to bring me to my senses and re-think the electronics .. a little more investigation and it turned out that the arc burns on both contacts were needing a sanding down .. and by doing so .. it presented proper metal to metal contact as opposed to arc-burn residue to arc-burn residue contact .. which (i guess) did provide sufficient metal surface to metal surface contact for electrical current to go through .. any hoot ... one $2 dollar file saved my >$200 pump!! woo hoo!!

[Poconos]

Another cheap success story. You got it right in that every time the contacts make and break there is a small arc and some metal melts causing roughness on the contact surface. Eventually the contacts may not make a good electrical connection and all it takes is a little movement (2x4 shock) to cause them to make contact. Some relay contacts actually do a slight wiping action when coming together which tends to keep the contact surface clean and smooth. If the 2x4 trick works then it's time to open the case and clean the contacts. To restate something, it is best to use a file instead of sandpaper because sandpaper can leave grit embedded in the soft contact metal.
Al

[njpool]

Would a nail file suffice? Or would that leave a bit of grit or be too wide?

[Poconos]

Best alternative to a file would be a strip of that wet-or-dry 600 grit paper. Cut a strip and fold it over a thinned down popsicle stick or something like that to resemble a file. I don't use nail files, I bite my fingernails, but I suspect it may be too coarse anyhow. Or just fold the paper over on itself and push-pull it between the contacts. You only have to burnish the contacts which means you don't have to take much metal off. Just clean them up a bit.
Al

[wgregww]

I wish I could see the pic.

[PoolDoc]

I wish I could see the pic.

You can, now. It had been lost, but I restored it from an archival copy.