1988 DX--temperature gauge used to read erratically; would be fine sometimes, would shoot up to hot at others, would not register still at others. Had new motor dropped in because old one was shot. Ever since swap, temperature gauge has not read anything. Period. Attatched new temp sending unit to wiring harness and placed against metal surface to ground, gauge still didn't read anything. Is this a proper test of the sending unit? If it's not the unit, are the only possibilities then the gauge itself or the gauge wire? Help!!