I acquired my '07 Convertible from the US last August.
Since I am in Canada, the warranty won't take effect in Canada until the car gets 12,000 km and I have it in Canada at least 6 months.
When I got the car it had about 8500 km on it.

Since then, we have driven it, autocrossed it, etc., generally having fun.

Last October, when we were autocrossing it (during a rainy day), we encountered several large puddles of water on the track, and the autocross course took us right through these puddles. I would say the greatest depth was no more than 2 inches.

I noticed, after this autocross day, that the horn was very "sick".
You know, it would sort of honk.... but very weak, and garbled.

Knowing that I wasn't going to do anything within the warranty for a few months I just ignored it.... accepting that whenever I honked the horn, it sounded like a very sick cow.

Occasionally, I would press and hold the horn button for several seconds, to see if the problem might "correct itself" (haha).

Last Friday I was trying to "correct" the horn again, by holding the button for several seconds. This time, after a few seconds, the horn stopped completely... and then the dreaded "Service Charging System" message came up on the DIC.

OK, I now have over 12000 km on the car, so off to my dealer this morning.
They discovered 2 (TWO) completely shorted out horns.
This was due to water entering the horns, and eventually corroding things inside, which caused the dead short in both.

This is due to the GM Engineering design of installing the horns so they face UPWARDS, creating a handy collection basket for any measurable amount of water. Of course, the shorts also blew the horn fuse.

The dealer replaced both horns, and installed them facing DOWNWARDS (how innovative !!!!). They had to make up new harness "parts" to fit the newer horns, and they replaced the fuse.
They then reset the computer to remove the code set.

PRESTO.... all is now good.

So, for those of you who are encountering the "Service Charging System" message, you MIGHT want to check your horns. Even though they may be sounding OK, they still might be shorting, causing the message.

Or, if you live in a wet (rainy) area, it might be an idea to turn your horns downward anyway.

 

Very good info, thanks for the heads up, could save some people from chasing their tails.

 

there is a new harness that could have been ordered with the horns to prevent cutting and splicing the old one. You might want to get it and have it installed. Would only take a few minutes.