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Hello there, does anyone know why my amplifier is switching to protection mode (ie turn off) but only when the engine is on. When the car is turned off I can get the volume up to 30 without the amp going into protection mode and when the engine is turned on with the volume set to 27 the amp will go into protection mode!! Thanks in advance

Sounds like it's not getting enough power. Or the earth is bad

I doubt the earth is bad because I have also tried it with 2 earth points connected simultaneously ... still same problem. Could it be because the wires for the signal from the head unit are not in the best condition (they snapped and I re-connected them instead of replacing...too much hassle to replace)

It could be but I'd imagine it's more to do with power when it o ly works the car off. Check the connection where it snapped and work from there

could it be that the alternator is not giving enough power to the battery therefore with the engine on (coils and stuff drawing power as well) the amp does not get enough power? so maybe a capacitor will solve the problem?

I'd be looking at battery and alternator first... Do the usual tests to check voltages, and check it's charging properly...
Unlikely to be a short in the signal cable - the input end of an amp can't usually tell. That, and you'd have a horrific buzzing, or very low output.

Protection mode will either point to a power supply issue, or output issue. As it works when the engine's off, it's unlikely to be output, unless there's a VERY loose or oxidised connection that's breaking with the vibration of the engine/music.