Is it normal for an Alternator to generate 15 V+ output?

The refrigerator on my Class C MH (2020 Coachmen Freelander on Chevy 4500 chassis) runs on 12V DC only. Recently, the refrigerator controller started to put out error code indicating “the operating voltage out of range”. Since this specific error/problem happens only during driving, I was then able to correlate it to the chassis alternator; When the engine is running the alternator would also charge the house battery, from which the house refrigerator draws its power. So, when the engine is running, I measured the voltage at the house battery terminals to be 15.4V, which I was able to confirm to be the cause for the refrigerator “operating voltage out of range” and the consequent power cut-off error. The operating range is 10.4 – 14.2V.

So, the question is: is the behavior of this alternator normal – operating in a typical range? Or is it showing signs of going defect? Not very knowledgeable about Alternators, somehow I feel it is not right. I could leave the alternator alone since I haven’t noticed anything else being wrong about the vehicle (yet), in the meantime, just to power down the refrigerator during the vehicle is moving and to turn it back on after set up camp to circumvent the problem. However it is not a solution really.

Thanks in advance for any insight or suggestion.