This 70 cluster I've been working with has been spotty: the rally gauge has been iffy: it almost always notes an empty tank. The left turn seems to only work with the lights on. The dimmer's questionable. I figured these would all work themselves out when the new Letric harness was installed, the dash bulbs were replaced, a new tach has been installed, etc. And now this "freshened" one is still showing the same symptoms. Between dealing with all the garbage China Parts Place and OPGI parts, I've about reached my limit on frustration. Does anyone do any sort of wiring checking on dashes & all its components? I'm curious if someone does this as a service.
When I restored the dash in mine, it had multiple different issues, which may be your case. Speedo was way off by 10 mph (it was shot and had to be replaced), fuel gauge was dicey (sending unit in the tank needed replacing), bad turn signal light sockets in the bumpers (a common problem with those GM sockets) that made the dash indicator lights do funky things, bad grounds, etc. Took a lot of trial and error to finally work all the bugs out... it was definitely frustrating.
