Nissan Repair: 1976 280Z erratic gauges, curcuit board, 1976 280z

Question
Erratic gauge problems on 1976 280Z with 104,040 miles: (1) Clock stopped more than a year ago, (2) voltage has always indicated about 15 mark when driving, (3) for past couple of years,  fuel gauge varied from zero to 3/4 even when tank is filled, and most often at zero, (4) For past 3 months, temp gauge varied from zero to hot side after warm-up. gauge erratic during extended freeway driving.....zero and then suddenly around 220 to 220+, (5) oil pressure gauge registered normally in center until 2 days ago when it ranged from zero to 1/4 mark, though oil level is on 'H' mark.

Note! All fuses in passenger-side fuse box check out OK. Radiator is full. Car had full service a month ago, but just discovered yesterday that 3 spark plugs were loose with oil seeping around the edges. This may account for the engine seemingly running hot and occasional problem of restarting after 15-30 minute shutdown. In those cases it took several cranks and a bit of rough running after it did fire up with the hot engine. No problem in starting cold engine.

Any assistance or guidance to problems will be greatly appreciated.

Answer
Jerry,

The instrument cluster is the most common problem.  The connections on the back side are either loose or the printed curcuit board (flex type) needs to be cleaned where it connects to the cluster and the harness.  Another issue is the drop resistor for the cluster; located on the back of the cluster.  The clock is a seperate issue and should be removed and the harness checked for power.  Most of the time the clock just quits and needs to be replaced.
Tight sparkplugs are a must and if the engine has a propensity of loosening them just keep an eye on them and that should correct erratic running.