electrical problem
 

I am working on a 1982 Targa 911. Took it down the road for a test drive after replacing the fuel injector seals and the Tach and Radio started doing strange things. The Tack needle jumped up to 8K RPM and kinda bounced around while cruising at 60MPH in 5th gear. At the same time the Radio started loosing electrical power and would go on and shut off. I wouldn't think the radio and tach are electrically related in anyway, but when this problem occurs both instruments start doing these unusual things.

Any suggestions?

Thanks,
Keith:confused:

Sounds like voltage regulator is spiking. Did you disturb any electrical connections?

I did not disturb any wiring at all. The owner recently installed a aftermarket radio. But I have done nothing to the car electrically.

Could be ground OR power poor connection(s). The FIRST place to check is the LAST place someone had their fingers in. This is a mechanics mantra because it's true!

electrical problem
 

The owner had the engine rebuilt about a year ago. Could be something that has just now surfaced from a improperly placed wire / loose connection. I'm gonna trace down the radio and tach wiring first. This car has a new battery and if the car is not driven every day, the battery will go dead. Could be a short somewhere too i guess. I charged the battery and drove it about 20 miles the other day but battery didnt charge enough to start engine after that drive. Thought that was unusual.

Thanks,
Keith

Time to check the voltage output on your alternator AND have the battery tested; it sounds like your alternator, or regulator, is screwy.
Charge your battery with a charger, NOT on the car. Have it tested at a shop; even a new battery can go south.
Voltage should be around ~12V standing, and ~14V when running.

gunter gave good advice..
ryan