Sometimes you get a bad contact on electrical components due to too high a resistance in contamination of the surface of contacts. I have never understood what it is but it used to be a common practise to clean the edge connectors on computer boards with a clean ink eraser before replacing a component. It is amazing how often it works. Since learning that trick I have removed and replaced motorcycle relays and ECU connectors two or three times to rub the contact surfaces together and ensure good contacts before rushing for a replacement.

Peter

[Linked Image]