Mondial 3.2 Odometer Problem - turns at idle!

A friend of mine has a 1986 Mondial 3.2 Coupe (USA) with 49K miles. The car just had a major engine out service and upon going for a test drive he noticed that the odometer turns when the car idles. In other words, if he starts the car and lets it idle the odometer will turn and increase the mileage at a very fast rate. The odometer changed 7 miles in 2-3 minutes before he noticed the problem. We doubled checked all the connections and everything appears to be OK. The speedometer still works, so it appears that the transducer from the transmission is working.

It is my understanding that the Mondial has a known issue with the odometer crapping out (technical term). There is a circuit board or a computer chip that stops working and causes the odometer to act funny. Is there a way to confirm that the circuit board or computer chip for the odometer is bad? If this is the case, where can I get a repair part. Finally, the odometer for Mondial is mounted on the dash and is seperate from the speedometer.

Any help is appreciated.

Ken