I hope those who are reading this post are aware that both the air con compressor and alternator are coupled with the
engine. So my question is, the engine speed is never constant. It may me idle, running in top sp[eed...etc. So, these devices, say the air con compressor, would it be at its max efficieny when the engine is running at top speed?

Similarly the alternator will charge the batteries perfectly when the engine is running at the top speed?

Or, is there a speed governer?