This concerns our 1999 V70 GLT. Often, when I first turn on the stereo (cassette & CD type), the small speaker on the right side of the dash is not on. What I do is to then put the balance all the way to the right, and turn up the volume. The speaker pops in after a few seconds, and works for the rest of the drive, and usually for several more drives.

My question is, is this likely a problem with the stereo or the speaker? Seems more likely a speaker problem since the larger right speaker in the door always works. If it is the speaker, what causes the malfunction?

Finally, if I replace the speaker, should I also replace the corresponding left small speaker for some type of balancing, or other, reason. Will replacing just those two mess up my stereo?

Don't buy anything until you've ruled out the wires in the back of the radio.

I have a '95 850T that had this intermittent problem as well. If I were to hit hard bumps the left speaker would come to life. I took out the radio and everything was plugged, just fine. But, when I moved the wires that lead to the plug, the speaker would come back to life. I tied ALL the wires together, where the defective spot seemed to be, with a tie and its been fine ever since. After a few years, they can become weak at the bend.

Check the board for items relating to cleaning the tuning mechanism (though that's probably not it)--note that if you have one of the SC-series radios, it will be a different deal from the CR-series.
If you do replace the speakers, check the ohm rating first; if the dash speakers are on a separate set of channels, they will be 4-ohm; if they are in parallel with the door speakers, both sets will be 8-ohm. It will likely be marked on the back of the speaker magnet. Replacing an 8-ohm speaker with a 4-ohm can cause a frying sound and possibly smoke from the head unit. Not recommended. Let us know what you find/do, especially if you find a set of replacement speakers that is a good fit and quality. Note: Crutchfield's isn't always right, but it's a good place to start.
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We have met the enemy and they is us. [Pogo] S70 cop car : Rough Rider tires& suspension, Walmart fog lights, eBay speakers, ambiance by Pall Mall, trim by Le Duc d'Tape, 8-channel THD by OEM amps