Ground Loop help

Again I griev....working out my alternator whine....
to recap...i have my sled and my sony grounded to a pigtail to the stock wiring harness grounding point.

I have the Rio HU grounded to a separate lead in the trunk where the amps are gounded

I have alternator whine

I disconnected the ground in the trunk and the whine stayed the same (read: the ground in the trunk for the HU was not effective)

to shorten this gorund run i cut the wire from the Rio

the whine went away! :-)

pushed everything back into the dash (which is a daunting task in a Miata) and all was fine ...but...throughout the week the whine slowly crept back into the system. :-(

a few notes of importance:

1-when i disconnect the sled/sony ground from the stock wiring harness the noise in umbearable (so i know tha this ground is somewhat effective)

2-When I pigtail in the ground wire from the Rio into the Stock Ground point with the other 2 grounds...no change...audible whine still present

3-On occasion...when the noise is louder than usual...i push in the left side of the Rio further into the sled and the noise quiets down..to the level that it is quieter but still annoying

Question:

Where is this "floating" noise being generated from and why did it take a few days to resurface?



1.

why did it take a few days to resurface?

Just a wild shot, but it sounds like electrochemistry - a connection between the empeg and the sled corroding or oxidizing and reducing the electrical contact. Pressing the empeg could scratch and thus clean the contact point, or move the contact point to a clean spot.

Hmm... If that were the case, then removing and reinserting the empeg a few times should reduce the whine the same as pressing it by scraping the contact - unless the ground moves completely when you press it.

Does an empeg ground through the sled or the docking connector/harness or both (or are they electrically the same and is that a silly question)?

Once upon a time, in a car far, far away, I had an early pull out radio that I had to use contact cleaner on the docking connector every now and again to keep it happy.

-jk

I have grounded the sled..I have NOT grounded the Rio...as such..the black ground wire that comes out of the wire harness on the sled for the HU is not attached to anything. But as i said...when I hook up this wire there is no change at all (read: while persists)

Seems to me that would indicate that there is a break in the ground path somewhere, either in the player, or in the sled connector. Perhaps getting a VOM and inserting the player with the top off in the sled and then testing for continuity would be advisable.

What is a VOM?

Also, is it possible that a dry solder joint where the IDE cable connector attaches to the motherboard cause such a break?

Volt Ohm Meter (ie a meter that you can check resistance and voltage with)

I'd say get a digital multimeter - decent ones are to be had from about $20 or so.

Yes, a dry solder joint could possibly break a ground connection.

/Michael