Car Stereos: Radio blown up because of installation?, radio chassis, metal brackets

Question
Hi. I had a customer install a Pioneer radio himself. He gave me the car to run an amp for his interiors. I pulled out the radio and noticed that the radio was grounded to itself. My first question is to explain how thats wrong. So after I seen that I immidiatly hooked the ground to up accordingly to the CAR chassis NOT THE RADIO CHASSIS. Once I fixed this problem, A new one arose. His navigation didnt work so I sent it out for repair. The person that Im dealing with said that the navigation bored blew up because it was shorted. The customer thinks that this is my fault because it was working fine when he brought it to me . Can you explain to me how fixing the ground would cause such a problem and why grounding a radio to itself is not acceptable. Thank you !
           Dave

Answer
Hi Dave,

I'm not quite clear on exactly what happened with the navigation.  Was the navigation function built into the Pioneer deck, or was it a separate component?  In either case, I don't see why re-grounding the head unit should have affected it.

You don't say what kind of vehicle this is.  In some cases, connecting the deck ground to the radio chassis might be acceptable.  For example, most Nissan radios don't use a ground wire in the radio harness; the factory radio is grounded through the metal mounting brackets.  The ground path is completed when you screw the mounting brackets to the dash structure.  If you're installing a new deck into a Nissan, and you're using the original metal brackets to mount the new deck, then you could connect the deck's ground wire directly to the chassis.  Like the factory radio, the ground path would be completed once the brackets were screwed into place.  

There's not really any difference between grounding the deck through the brackets to the dash metal, versus connecting the ground wire to the dash metal directly.  However, this would mean that the deck would no longer be grounded once it was unscrewed from the dash.  In this case, the deck would try to ground itself through other connections: the antenna plug, RCA cables, or another external component connected to the head unit.

Of course, if the deck isn't mounted directly to the dash with metal brackets, then connecting the ground wire to the deck chassis would be pretty useless.  Just like the situation with the unmounted deck, it will try to find a ground path through the other connected components.  Pioneer decks have a common problem that originates when too much current runs through the RCA cables' signal ground.  If the navigation unit that was damaged was a separate component, it's possible that this kind of ground current may have damaged it as well.  But I haven't heard of a similar case before this, so it's just speculation.

Hope this helps!

Brian