Joined: Aug 2009
Location: Sunshine Coast, Queensland, Australia
Try to find the instrument relay , should be near the fuse box. I think you might have a problem similar to one I had on my 1986 Pulsar. One relay handles both gauges, swap over with another one of the relays and see if the instruments work ok. I'm not sure on the 720 but I think the relay will be one of the ones above the fuse box on the interior kickpanel.
Aussie 1986 N12 PULSAR 24 years,250000km one owner, still going strong!