My battery went dead on my '86 coupe. After jump starting it, I noticed the digial volt readout was 9.9v, the coolant temp was 172deg, the oil pressure was 72lbs, and the oil temp was 125 degrees. I charged the battery to 13.2v (using a battery charger), the car starts and runs great, but these digital readouts haven't changed. All the other readouts seem to be normal---tach, speedometer and gas gauge all work, as well as the average & instantaneous mileage. Also, when I change the readout from volts to coolant temperature, the readout changes then immediately goes back to 9.9v.
any ideas what might be causing the problem??