My friend has a '90 GTU with a rebuilt motor and an aftermarket head unit. It's been running great until today.

The radio began turning on and off. Then the volt meter gauge would start spiking like crazy, like the alternator was drawing too much power for it to handle. The idle would match the spiking. All the dash diagnostic lights would flicker.

We jump started it (the battery was drained) and it didn't stay running for long.

What would be the first places to look? I'm thinking it's most likely a ground issue, but what actual locations on the car should I look at?

 

sounds more like the alternator failing....
check state of battery and verify alternator is putting out about 14.5 volts at about 2500 rpms. a lot of shops will test starting and charging system for free. it only takes about 3 minutes.

 

Yeah that's what I thought.. since the battery doesn't have to be good to keep the car running, correct?

He said the alternator was fine which is why I threw out that idea, but maybe HE could be wrong

 

Go through the fuse box with the car off and look for a drain