Help with grounding head unit.

[Shadowborg]

Hey guys. I've been having issues with my stereo whining and popping. I initially had the head unit ground wire connected to the wiring harness, so I ran a new wire from a bolt near the hood release to the head unit area. Then I cut the ground wire coming out of the head unit and temporarily twisted the wires together just to see if it would help. Turned the car on, same problem. For some reason I decided to take the wires apart. Nothing changed. I didn't think a head unit would work without being grounded. What gives?

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[Boomin_tahoe 5,000+ posts]

Are you running an amp by chance? Could be RCA's too.

 

[poolman966554]

prolly still working through the antenna ground(most likely), or chassis ground. Are you running factory speakers? or have amps??

That said, if you have amp connected, ive had best luck grounding the outer ring portion of the rca at the head unit.

 

[Shadowborg]

Yeah I've got aftermarket amp, speakers and subs. The noise happens even with rca's unplugged, though it is much quieter. There is also loud popping when I use my power seat controls on the door, even with rcas unplugged. I checked the resistance between my amp and its ground. it was under 1 ohm. I tried putting a bit of wire on one of the rca inputs and touching it to the metal of the HU, no change.

 

[Boomin_tahoe 5,000+ posts]

It could very well be your amps ground....causing issues to other things.

 

[Shadowborg]

I'm a total noob at this. Doesn't it mean a ground is "good" if it measures less than 1 ohm resistance?

 

[Boomin_tahoe 5,000+ posts]

I think "0" is what your wanting. Not sure....I don't measure my grounds.

 

[Shadowborg]

So will a head unit work without being grounded or no? If it won't it must still be grounded through the antenna wire.

 

[wew lad 5,000+ posts]

you're not going to get a good idea of the ground resistance measuring it with resistance, it's not under load.

obviously more than 1 ohm is a sign of an issue but you're better off measuring voltage at the ground to the positive and comparing it to ground to the positive at the source.. the battery/alternator

 

[Boomin_tahoe 5,000+ posts]

So will a head unit work without being grounded or no? If it won't it must still be grounded through the antenna wire.

Why must it be grounded thru the antenna wire? Should be both separately. HU ground is a must, yes, in order for it to work. ALL electronics must be grounded.

What vehicle are we talking about here? I don't think you ever mentioned it.

 

[Shadowborg]

I meant it must be grounded through the antenna wire because it was functioning with the actual ground wire disconnected. I confirmed this by unplugging the antenna wire and it wouldn't turn on. Then I'm thinking maybe I'll just leave the antenna wire unplugged and try to connect only the ground wire. Same noise. I tried wrapping a wire around one of the RCA jackets and touching it to the new ground wire I ran earlier. Noise got worse. I checked the resistance of the amp ground again and it actually read -0.09. is negative resistance unusual? I will try checking the voltage difference next. Again sorry if any of this sounds dumb, total newbie. Oh and the car is a 2002 grand marquis btw.

EDIT: Voltage between amp power and ground: 13.5

Voltage between batt pos and neg: 13.59

 

[Boomin_tahoe 5,000+ posts]

Are you talking about antenna wire to your car? Now I might be confused...

 

[Shadowborg]

The thicker wire that plugs in, not the one in the wire harness.

 

[Boomin_tahoe 5,000+ posts]

ok..

 

[Shadowborg]

also, just for shits and giggles, I measured resistance between the two halves of the initial ground from the back of the HU into the factory wiring that I cut into earlier, it measured -40. As well as checking between the wire coming out the back of the HU to the new ground wire I ran earlier. What's up with that? Good or bad?

Edit: If I swap the leads around, it reads 40.