The thing is that the "12 v" supply is subject to NASTY transients, particularly during load dumping from the alternator- you CAN occasionally find 100 V spikes from that kind of event. With the scheme you have being theoretically well immunised to conducted EMC, your main worry is more likely to be radiated EMC and supply transients killing the DC inverter.

Stephane Rey who posts here quite a lot has a lot of automotive engineering experience.


Steve