I wonder if this guy can fix them? They fix a lot of other "non-repairable" stuff like Garmin GPSs etc.
I had already communicated with this company before we ordered the battery as I didn't think that replacing the battery would fix the problem. Based on their response it does not sound like Sena products are really in their wheel house. He said that they have worked on only a few of them. Some they were able to fix and some they were not. However, they have a very reasonable charge for testing and providing an estimate. If they report back that they cannot fix it the charge for the evaluation will be less than what the new battery cost. In retrospect it would have been a good idea to send it to them first instead of changing the battery I guess.
Sometime in the new year this unit will probably be sent to them to see what they say.
I haven't been here for a while so here is an update of what has transpired with this Sena 20S.
I had previously written that from the very beginning I suspected that this was not a battery issue because when it is plugged in to a charger it reacts exactly the same way. While not a guarantee, generally speaking plugging an item it in to a charger eliminates the battery as the cause of a problem. Unfortunately this suspicion turned out to be the case. Dubious as we were we ordered a replacement battery as this was the most offered suggested fix. The battery was replaced and then the unit was put on charge before we tried to power it on. It did go through its charging cycle as it normally does until it showed that it had achieved full charge. Presumably this is an indication that everything related to the new battery and its installation are OK.
When we powered it on it did exactly the same thing as it did previously with the old battery. We tried several times with the same result. We also tried it several times with it plugged in to a charger. We went through the reset procedure several times with no effect. It still does not work.
Just as a recap for reference in case this is of any use to anyone in the future who is experiencing a similar problem with a Sena 20S.
Normal operation:
When the Sena 20S is turned on the following happens;
The LED light flashes blue once.
If the unit is connected to the speakers there will be three tones heard followed by the voice saying Hello!.
Then the LED light flashes red three times.
Then the LED light returns to flashing blue to indicate that the unit has gone in to standby mode.
Defective operation:
When the Sena 20S is turned on the following happens;
The LED light flashes blue once.
If the unit is connected to the speakers there will be three tones heard followed by the voice saying Hello!.
Then the LED light flashes red three times.
Then the LED light flashes blue but it will only flash blue one time.
Then the unit immediately turns itself off.
There are no tones or voice saying goodbye when it turns off. It just instantly shuts down.