With my radio, I have found that moving the fader button solved some of my problems. Just go right to left about a dozen times to help clear the internal contacts. Volume also seems to make a difference, low allows the speakers to go out, and high volume brings them back.
Probably a spider in the works :)

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)

I have a similar issue with my speakers in a 99 V70. When you say R/H, do you mean the entire right channel, all 4 speakers on the right side? I ask because my right front door speaker goes in and out, and I believe it's because of corrosion on the contact at the speaker itself in the door. If I up the volume on my radio enough, the speaker comes back on, most likely because the increased current overcomes whatever resistive path the corrosion is adding.

So if your failure is in one or both of the right door speakers (where water can get in), play with the volume, and think about opening the door panel and cleaning that contact. If the entire right side is out (including the dash and rear speaker) irrespective of volume, I'd guess one of the amps inside the radio has blown. There are usually one or two amps per channel, depending on how it was designed. When those blow, you'll need to find a replacement radio.