I have two Harbor Freight digital calipers, item #47257, and I've had=20 problems with one of them especially, where the display will go blank. = It=20 seemed to work sometimes if I squeezed the enclosure, and I thought it = was a=20 bad battery or bad connection. But a fresh battery didn't work.
So I took it apart, which meant peeling off a foil backing to expose = four=20 small phillips head screws, which removed the electronics module, and = then I=20 removed the PC board with four even smaller phillips screws. The LCD = display=20 connects to the board with a flexible conductive strip, which relies on=20 pressure to maintain contact. I cleaned it and the mating contacts on = the=20 PCB, reassembled it, and it now works fine!
My house is always very humid and I think that's what caused the = problem.=20 It's hell on all my tools. Everything is rusty or mildewed.
It's quite interesting to see the mechanism that is used to make=20 measurements. There is an array of PCB traces that are aligned with an = array=20 of stripes along the length of the caliper, and (I assume) these create=20 pulses that are counted as the head is moved. But it also needs to know=20 which way the head is being moved. Probably something like a quadrature=20 encoder as used for rotary position sensing. I'll have to look it up.