I have a 2000 Volvo S80 T6. It has approximately 80,000 miles. I'm having an issue and would like to get someone elses opinion.

I have the GPS and when I first started the car, the screen was really dark. It was really cold so I just assumed that it needed to warm up. Later when on the freeway with the cruise control on, the speed of the car felt as though the car was accelerating up and down.

On the return trip home, I set the cruise control again. It continued feel as it was accelerating up and down but late, the cruise quit. The cruise light went out and did not/would not come back on. Sometime after, the car started really acting odd. It began to accelerate up and down when driving down the road. It felt as though it was going to stall. I pulled over and turned the car off. It restarted. When driving it was really jerky. The cruise worked. I shut all electrical equipment off. It ran ok.

Then, the car began to really have a hard time with power. I had to rev the engine and it would jack rabbit accelerate. The lights seemed to be dim. I turned the GPS on which seemed to cause the Service Engine message to display. The message did not come on until I turned the GPS on.

The headlights seem to be dimmer than usual. When I rev the engine while in park, the lights seem to go up and down.

My educated guess is that the alternator is going. I replaced the battery during the summer. I don't want to take the thing apart without diagnosing it. Any advice would be greatly appreciated!

Thanks in advance.

Roddy