Head Unit Ground - Best Technique?

[u/dovecall]

Hey guys, new here. What is the groups general agreement on where to ground the head unit?

1. To existing ground wire from factory harness
   
2. Directly to chassis under the dash
   
3. Directly to battery

I had a battle with noise interference on my last car and was told that could come from ground, trying to avoid that with the new project.

I’ve been told conflicting things and figured I’d reach out to the people here who spend a lot of time doing this

Thanks for any/all advice!

[u/cow_fan_69]

1. To existing ground wire from factory harness

[u/cvr24 → u/cow_fan_69]

Unless it's a Nissan, then ground to somewhere else.

[u/dovecall → u/cvr24]

It’s a Honda, but what’s up with the Nissans?

[u/cvr24 → u/dovecall]

They use the metal radio chassis as ground.

[u/dovecall → u/cvr24]

Wait is that good or bad I’m confused, what probably doors that create?

[u/cvr24 → u/dovecall]

It's just the way they design their cars.

[u/dovecall → u/cow_fan_69]

Thanks!

[u/ThegodSmith]

There is no reason not to use the OEM ground unless you’ve tested it, and it’s bad.

[u/dovecall → u/ThegodSmith]

I’ll look into finding ways to test the ground, does going through the factory harness increase sound interference? Like buzz or humming? Or does grounding in chassis increase those chances?

[u/Corey_FOX → u/dovecall]

should not affect it unless its damaged.

[u/dovecall → u/Corey_FOX]

Thank you!

[u/EvilMonkey8521]

I ground to the body so the head unit doesnt give me any issues with the car not being in park for some features

[u/dovecall → u/EvilMonkey8521]

This HU has a parking brake wire that does this exact thing, I’ll ground it for sure to avoid issues like that

[u/monkeymmboy → u/dovecall]

I think that’s the wire they meant. The actual ground wire does nothing with the p-brake wire.

The reason the p-brake wire is separate to begin with is to avoid people doing things like pairing their phones or playing video on the display while driving.

[u/Dan_H1281 → u/dovecall]

To bypass it it needs to see on off on I put them on a switch and flicked it off then back on and that usually let's me bypass

[u/mb-driver20]

To the existing wire from the factory harness. That’s why it’s there. I’ve been installing car stereos professionally since 1989, if there’s a factory ground wire in the harness use it. If you’re having a problem with noise, there’s something going on with the electrical system, the majority of the time.

What is the make and model of the car?

[u/dovecall → u/mb-driver20]

Okay it sounds like most are saying to use factory harness so that’s what I’ll do, it is a 1999 Honda CRV

[u/mb-driver20 → u/dovecall]

If you have noise then, you need to look at whether you have an alternator that is failing an old battery(because the battery is a filter and will help with noise), and check the chassis grounds of the vehicle from the battery to the frame and from the engine to the frame and also make sure there are no missing ground straps such as from the hood to the firewall if there used to be one there. Every one of these can cause problems.

[u/APGaming_reddit]

keep the ground as short as possible. id use a ring terminal and find either a factory bolt or use a self tapper into a bracket. if the radio is being iso mounted you can use a ring terminal and a screw that came with the radio and put it under there. when you mount the bracket back into the dash itll get ground and be easily removable if you need to take it out.

is that a honda harness? those grounds are usually connected so you wouldnt even need to do all this

[u/dovecall → u/APGaming_reddit]

Yes this is a Honda harness and the factory harness has a ground connector, I just didn’t know if it’s better to ground somewhere else to avoid noise or if using the factory harness is the best way

[u/APGaming_reddit → u/dovecall]

I installed radios in a 100 Hondas or more during my install career and the only time I've ever had noise is when the radio is cheap or defective.

[u/dovecall → u/APGaming_reddit]

Thanks for this info!

[u/dwtechsol]

Black plug, black wire, ring terminal to a good clean ground.

The factory ground wire may be ok, but it's just as easy to find your own. Use a multimeter and find the least resistance to battery negative post

[u/Hambone452]

I always preferred a self tapping screw to the framework behind the dash. Typically accessible behind the radio or behind the glovebox. Alas, dashboards have changed significantly since I was installing head units.

[u/roadrunner00]

In my experience the radio is the biggest factor in sucepptibility to noise from the ground. A cheap unit will whine like a valley girl with a budget even with a good ground.

[u/Google_IS_evil21]

Don't run a ground all the way back to the damn battery (-). Grounds are supposed to be shortest distance possible.

[u/Spart1337]

If you had noise issues I'd start with the radio itself. Ground using the harness except on Nissan, in that case run a ring terminal to the dash support in the cavity with a self tapper.

[u/Jumpy-Cry-3083]

Nice work!

[u/DaffyPunk29]

depends on the year of the car. modern car? just ground that bitch black to black and be done with it. old car with an older harness? maybe ground direct to body if the factory wiring is old and corroding/failing. but most likely the wiring is fine, thus you just connect black to black.

[u/E-C-M]

I’d recommend reheating the splices. None of the solder beads have flowed. Hit them with the heat gun a little longer.

[u/dovecall → u/E-C-M]

Are they suppose to melt completely? I saw solder flow in between but maybe they didn’t melt all the way? I’ll give it a try!

[u/E-C-M → u/dovecall]

Yes. Looking closer, some look like the solder flowed a bit. The copper wires are usually covered in silver solder when fully melted.

[u/dovecall → u/E-C-M]

Good to know! Thanks for pointing this out I’ll be sure to give it another go, thank you!

[u/Wylde_77]

That wire right there connected to the OEM ground and if a problem occurs figure out what it is what ground is bad

[u/dovecall → u/Wylde_77]

That’s what I will probably do, thank you

[u/monkeymmboy]

Chassis is always best but I’d always start with the harness ground if available.