I'd call Becker first at 201-773-0976. They will offer a little diagnostic help on the phone. I'd also search "1492 & 1692 phone" in the audio forum. I think this question has been asked and answered. I've seen discrepancies regarding the "exact" speaker wiring for the phone. However, the essence is when the phone is used all the speakers are muted except the right dash speaker. You can easily remove [unscrew] the inner plastic container in the center console to check the wiring there. It's CAT 5 if you're ethernet aware.

In the attached pik of the connections at back of head unit, you'll notice Pin 3 of A is for the speaker muting. Unfortunately, I'm not sure how it functions, but it implies you may have a unintentional ground in the line.

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