I recently replaced the stock radio in my 1998 S70. The CD-player had died, and I had poor reception on both the AM and FM bands. After replacing it with a new Pioneer radio, I noticed an improvement in the FM reception, though it was not stellar, but the AM reception was still non-existent. I've ruled out the antenna as the culprit for the poor reception. I took it and connected it straight into the back of the new radio, and I had great FM reception, and good AM reception. This is probably because the antenna was retracted at that point, and could not pick up the full AM wavelength.

Having cleared the antenna as the problem, I hooked it back up in the trunk. There is a ring around the antenna plug where it is connected into the back of the radio. I took this ring off and as I inserted the plug into the radio the reception came in clearly on the FM band, and decently on AM band. I inserted the plug all the way into the radio, and the static on the AM got much worse. The FM stations sounded great. So, I drove around and noticed that as I accelerated the engine noise came through the speakers when I listened to AM, but the FM stations were fine.

I checked the antenna lead with a multi-meter and the lead coming from the antenna does not have any continuity. With that disconnected I checked the lead inside the dash, and that does have continuity.

So these symptoms point to two possible problems. 1) A bad antenna ground. Which, from what I understand is the sign of a bigger problem. or 2) A problem with the cable inside the dash. Which can be fixed with a three dollar part from Radioshack. Does anybody out there have any idea about what the problem is? Am I overlooking something simple? Let me know, baseball season is coming soon and I'd like to listen to the games in the car.