strange issue with head units, 94 lexus

Ok strange issue when I swapped out my head units

my Pioneer DEH-P8000R had gotten really dim. (worked great for years, but display had gotten dim in the last year)
all the wiring was properly matched to the original factory head unit, based on the factory shop manual

I picked up a Pioneer DEH-P360 hoping to just unplug the pioneer harness in back from the old one and plug into the newer one.

unfortunately the plugs weren't compatible
so I proceeded to move 1 wire at a time from the old harness to the new one.

But when I was done the unit would not turn on.
I rechecked everything almost 10 times!
still nothing, so on a whim. I connected the HU ground wire and attached it to a bolt inside the console and it worked!

For some reason the original factory ground wire did not work for the newer unit.

I went back and wired in the old HU to the factory ground and a 12v source and it worked again.
But the newer unit refuses to work with that particular ground!!!

this is the weirdest thing I've seen......

I do know that lexus (car is a 1994) uses a common ground for their speakers. And I had put in new ground wires for all the speakers, while retaining the factory positive wires.. maybe that might be a clue to the weird results???

but why did one hu work and not the other?

normally I wouldn't care, but now that I'm using the chassis as ground I have a horrible speaker whine.
The factory negative wire must have had some sort of way to prevent the whine

What can I do about the whine?

sorry for the long post
thanks

Is it possible that you had the antenna plugged in with the old radio and did not have it connected when you tried the new one?  The radio will ground through the antenna.   As for your noise, https://bcae1.com/images/rca/temporaryrcashieldrepair.html

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Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB

oh wow, I never considered that

the antenna wasn't plugged in while testing

I'll retest with the antenna plugged in and ground wired into the factory harness like before
thanks

From what you are saying, I believe there is a problem with your factory ground wire.  It will ground through the antenna, but if you know the ground is bad, ground it to the chassis, or metal in the dash.  I was just pointing out why I thought it was acting as it was. 

Did you catch the part that will fix the whining issue?

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Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB

There is one other way to fix your noise problem.....be rid "O" the Pioneer.

There have been LOADS of topics on such issues. Most, if not all, members come to the table with the same solution.

This one is just a sample....

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i am an idiot wrote:

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  As for your noise, https://bcae1.com/images/rca/temporaryrcashieldrepair.html

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Yeap I looked over the link,
but my HU powers the speakers, not a separate amp.
So no rca cables for the speakers
Tough I do have a separate amp for the subwoofer, but I don't think thats making the whining noise

KarTuneMan wrote:

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There is one other way to fix your noise problem.....be rid "O" the Pioneer.

There have been LOADS of topics on such issues. Most, if not all, members come to the table with the same solution.

This one is just a sample....

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thanks,
hmmm I've had 3 prior pioneer decks in different cars and never had a problem (tough they were all the higher end ones)
until now (which is a cheaper end pioneer)

I'll try a different ground point or one of those "loop" things


thanks guys

Just thought I'll contribute some of my findings

I re grounded everything to not much of any effect,
and since the dash was apart anyways, I wanted to see what would happen if I connected the ground wire to the previous ground wire (which was brown with black stripe)
Granted last time I did this the radio didn't work, but then the antenna wasn't plugged in; so basically it's grounding through the antenna, right?

After connecting the HU's black wire to the harnesses BROWN / black, it sounds 95% better
there is a tiny bit of whine, but I really have to listen for it, and can only hear it when the song has silent parts

But I still need to do some tweeking
cause my carputer screen's black wire is "tee-d" into the HU's black wire. And now the carputer is making 100% more noise and whine, DOH! lol
but at least the hu and ipod play relatively fine now


I also noticed another brown wire with a silver stripe.
I don't know what it is, but looking at the factory manual I see a ground and signal ground (both are mainly brown)
I'll need to find out the difference

There is a ground loop between the carputer and the stereo.  Call shops in your area and ask if they sell a PAC SNi-1,  Ask if you can try one on your system and see if it takes care of your problem.  They sell for around 20 bucks.  It should take care of your problem.

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Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB