Headunit loses sound when car lights turned on

[jon-dc5]

I just fitted my new jvc KW-XR411 double din headunit,i used the correct honda ISO adapter PC2-68-4,
Everything was plug and play,no joining wires,

The headunit is working perfectly,radio,cd etc, however when i turn on the car headlights it loses sound,
It works away fine,lights on,playing cd/radio,just no sound,

Anyone ever had this happen before? I did a quick google there and it came back as maybe the ground/earth wire,
I tried moving it around but no joy.Any idea's??

 

[leelee81]

I wonder if the dimmer wire on the car is somehow connecting to the mute wire on the head unit? :xconfused:

 

[jon-dc5]

Yea ive a feeling it's something to do with the dimmer wire, i thought with the honda ISO adapter
it would be plug and play though :xconfused:

 

[TyperItr]

Not too sure, but i know when lads put in 3 amps and 4 subs and stuff into the car, the alternator dose not have enough power to run them all and the lights, so something has to give in, when there is a beat in the song the headlights dim (thats what power capacitors are for, to stop this). But mabey its the opposite way around with you, when the light come on the sound dips as there is not enough power for both to run. How is your car battery and alternator? This is jus a possibility although i have never heard of it with just a standard stereo.

 

[jon-dc5]

I've no amps or subs,just the standard speakers, the battery seem's fine, same voltage showing up on the rsm
as always,

After some further fooling around with it i think it is the earth alright, with the earth bolted to a metal
part in the dash i've no sound with the car lights on but when i move the earth around by hand and touch it
off another metal part the sound comes back,only for a split second though,can't seem to keep the earth,

The original jap pioneer headunit i took out wasn't earthed to the car and it worked fine,
Maybe the ISO to honda harness is dodgy,i'll fool away some more and see,
Thanks for the replies!

 

[C&S Evo7]

it certainly sounds like a wiring issue, has the headunit ever worked? it may of course be faulty. it would take an auto spark 5 minutes to find your fault, where do you live?

 

[leelee81]

I've got a wiring diagram for the cars audio here somewhere. I could scan it and put it up if it will help? I used it to repair the wiring due to some monkey cutting into the loom rather than using a ISO plug :xconfused:

 

[C&S Evo7]

Sounds like the dimmer wire from the car loom is connected to the earth on the headunit, don't ask me how but there could be a mistake on the adaptor harness

When the headlamps are off the headlamp relay is not switched so the positive side will actually be earth,( dummer wire is negative) once the lights are on the relay energises and provides positive to the dimmer wire which means your headunit has no earth so the sound stops

 

[jon-dc5]

I've got a wiring diagram for the cars audio here somewhere. I could scan it and put it up if it will help? I used it to repair the wiring due to some monkey cutting into the loom rather than using a ISO plug :xconfused:

Thanks but i don't fancy going at the wires! i thought it would be just plug in the new ISO adaptor and work away,obviously not!

Sounds like the dimmer wire from the car loom is connected to the earth on the headunit, don't ask me how but there could be a mistake on the adaptor harness

When the headlamps are off the headlamp relay is not switched so the positive side will actually be earth,( dummer wire is negative) once the lights are on the relay energises and provides positive to the dimmer wire which means your headunit has no earth so the sound stops

That sounds like the problem alright,i also noticed the center console lights come on and off with the radio too,(heater control lights,hazard switch light,
the red light over the cup holders) it's a brand new headunit, i might order a different harness as they are cheap and try that.
Failing that the car is due for a service soon enough so i'll stick my old headunit in until then and get it properly looked at.Thanks!

 

[jon-dc5]

Quick update incase anyone else gets stuck with the same problem,
Sorted it there today,i got the jvc wiring diagram and matched it up to the ISO lead,
Two of the wires were in the wrong/different place,sorted them out,it's working perfect now.

 

[C&S Evo7]

which two wires?

 

[jon-dc5]

I found out the headunit doesn't have a automatic dimmer,it's controlled manually by a button on the headunit,
So the dimmer wire on the ISO harness (pc2-68-4) was running to the remote lead/power antenna wire on the jvc harness,
and the dash illumination wire on the ISO harness was running to the mobile phone system wire on the jvc harness.

I didn't need the remote lead/power antenna as i have no amps or power antenna and i don't have a phone kit
either so i disconnected these two wires from the ISO harness and it's working perfect now,
Fitted like a glove too! no new fascia surround needed.

It was my first time fitting a headunit,i was hoping it would be plug and play but it wasn't too hard of a fix in the end.
Some good info on fitting headunits in the I.C.E section on here too :xcheers: