The red light indicates that your amplifier is in protect mode. Amps go into this mode if there is something wrong with the setup of the system to prevent fatal damage to the amplifier circuitry. This is bad thing since the amplifier will not function until the problem is solve and it can remove itself from protection mode.
Amplifiers can go into protect mode for many reasons but one of the most common is incorrect mounting. Is your amp sitting on the metal of your vehicle? Is it bolted down and screwed into the metal of the vehicle or your seat? The amp should never be touching any sort of metal. Only the ground should touching the metal of your vehicle.
Speaking of grounds, many people often neglect proper grounding which can cause an amp to go into protect mode. Do you have a solid ground? Is the wire less than 3 feet long and directly connected to a non-painted metal part of your vehicle? Is the ground wire the same gauge as your power wire?
These are just a few reasons why an amp can go into protect mode. You can find more information here
. Or simply google for why your amp is in protect mode.