Diodes on Head Unit’s Negative?


CarAudio.com Newbie
Jul 2, 2021
Hey Everyone, Robbo here, from Australia.

I have been facing a hiss sound with my Nissan Patrol for months. I have taken it to multiple car audio installers and their complete failures owe me nearly $1,500AUD in labour fee’s.

To test the theory of it being a faulty head-unit, I took it out of the dash and dummied it straight to the positive and negatives of the under bonnet battery, I also dummied the park/remote wires and dummied a speaker (eliminating ignition, rca’s, amps etc), LO AND BEHOLD there was NO hissing sound, but SOON as I put the negative terminal back onto the battery the hiss comes back.
(Which would mean something is shorting on the ground of the vehicle?)
I cannot find the short (I presume it’s the vehicle immobilisation system given that it’s the only thing on while there’s no keys in the ignition) so my question is this; Can I instead just put an inline diode on the head units ground wire so that the current interference from the ground cannot pass into the head unit anymore?
Thanks everyone!

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