Moin, I have bought a new Pro German Audio WSK-4200C and since then have the problem that the power amplifier has switched to Protect after some time, as it has probably become too hot. It is mounted in the trunk on the rear bench, the mass I take at the attachment of the buckle belt and the underlying metal is smooth ground (resistance of the whole ground line over the body to the battery minus terminal 0.1-0.2 Ohm). The plus and the ground line are 20mm2 OFC cables. A In addition, a 1F condenser from Hifonics is installed. The 4 channel power amplifier is mounted on two channels and is operated thus a double 30 box with two impulses US Acoustics RW112, which have an RMS load of 500W and a resistance of 4 ohms, each running on a bridged channel. The mass cable which goes from the battery to the body has a cross section of 35mm2 and what goes from the engine to body 20mm2. My car is a Honda. Accord from 2001 and when I hear about 45 minutes on level 16 (of 50) it turns on in Protect. In addition, the power amplifier is fictitious as soon as the car is running. In addition, with a lot of bass, the indicator light flashes from the capacitor, so you should check the ground connection. I did, the said 0.1-0.2 ohms are, so actually fine. At volume 30 the voltage drops partly to 12.5V, but with the complete onboard network and the speed drops so ~200 rpm. Ask for help. Everything I’ve tried so far hasn’t worked.