Ground loop issue - 3000GT/Stealth International Message Center

993K · 04-15-2006, 03:26 PM

Okay, I am enjoying the ever popular alternator whine. I've read some of GMo's input on past problems to trouble shoot my issue. Here is what I have going on...

I can have the stereo off (and even disconnect the power and ground to the amp) and the whine is still there (although not through the speakers). Could it be coming through the underdash speaker for the beepers for the door also? When everything is hooked up it is noticeable at no or low volumes or when there isn't much bass through the stereo speakers. Its frequency and pitch is in direct relationship to the rpms of the motor.

Help! Its annoying the crap out of me!

streetracero1 · 04-15-2006, 04:23 PM

yea that sound is a pain in the ass i've delt with it many times. i always find it best to just pull everything out and reinstall it all thats normally makes life easier for me to find the problem but not nessaceray. its normally because an rca is ran too close to a power wire so try that

993K · 04-15-2006, 05:14 PM

Thanks for the input. I have the rca's running down teh opposite side of the car from the power wire so the only place they are close is by the amp. I made sure they were not close to each other and I still have the noise.

Of course, I was figuring this...the noise existing with the factory system before I ever installed new speakers and the amp. However, now with it in the system, its amplified more. It was easier to deal with the stock system at this point...

Anyone have any other ideas?

GMo · 04-15-2006, 06:12 PM

Alternator whine wouldn't be happening due to RCA's and power wires running too close with DC.

So, you have the amp(s) disconnected from the signal (RCA's) and still have whine...can you pinpoint the source of the noise? Have you had problems with your alternator? Have you been having problems with your battery?
I would have both of them tested if you can't figure this out, and I believe places like pepboys do it for free. You can use a multimeter or voltmeter on your battery to see if that's functioning correctly.

Anything which outputs pulse width modulation (computers. lights, amps, HU) can be causing the alt whine . It can be heard through any speaker which doesn't have a high pass filter under the audible frequency. I've seen aftermarket alarms causing it. If your HU is still connected to a speaker it could be causing it.

No matter what I would re-do your grounds, like I've previously explained. Check your battery for a proper voltage- whatever it's spec'd at , 12.6V or around there, and for a proper charging voltage, around 14V. If your battery is failing or cycled down, it could be the culprit.

993K · 04-15-2006, 08:41 PM

Well, my car has been idling low intermittently when I'm sitting at a light (no tune up due) and I have notice the battery gauge reading a bit low from time to time lately as well...

I didn't realize a low battery would cause the whine too. Wow, I hope that is it. I'm going to put it on the charger and see what happens (even if its a temp fix I can figure its time for a battery).

I did all the ohm measurements with grounds like you previously stated and everything was looking okay. I do not have any speakers hooked to the head unit and no alarm.

I do however have the speedometer pulse signal parallelled into the deck (it is a navigation unit that uses this signal for esimated positioning when the antenna cannot find a satelite (like when you are in a tunnel). I should disconnect that and see what happens.

Well, the battery first...

993K · 04-16-2006, 12:24 AM

Got the battery up to par again...no help with the noise. I haven't had any alternator problems but I guess I'll go have it tested. The more I think about the speed pulse, the more I figure that shouldn't effect things, right? It goes right into the HU and there are no speakers connected there...only RCA's.

GMo · 04-16-2006, 01:41 AM

Quote:

Originally Posted by 993K

Got the battery up to par again...no help with the noise. I haven't had any alternator problems but I guess I'll go have it tested.

I would definitely disconnect all of your sources, including the antenna if you unplug everything and it's still happening-as it's grounded to the chassis.

Quote:

Originally Posted by 993K

The more I think about the speed pulse, the more I figure that shouldn't effect things, right? It goes right into the HU and there are no speakers connected there...only RCA's.

Electrical signals take the path of least resistance and that would be any connection. Disconnect it and remove it from the chassis if it's grounded or bolted to it. That's fitting the alternator whine suspect list to a tee.

993K · 04-16-2006, 11:05 AM

What do you mean disconnect all of the sources? All wires to the HU?

GMo · 04-16-2006, 11:22 AM

Quote:

Originally Posted by 993K

What do you mean disconnect all of the sources? All wires to the HU?

No, disconnect all of your major electronics from their power/ground wires. Amps, HU, and your pulse signal, possibly antenna- (whatever else A/V you have powered).
Then one by one reattach them. Do this to determine the source of the noise. If you have all of your powered electronics disconnected, and you still hear alt whine, more than likely it's a wiring problem with the Battery/Alternator or one is failing. (diodes on the alt, or battery IR)

BTW, how is your HU grounded, and how is the pulse signal unit grounded?

993K · 04-16-2006, 12:27 PM

The HU is grounded to the chassis. I only have 1 amp and a Sirius tuner that has grounds in the trunk (they do share it trhough a distribution block). Ohm readings seem to be okay there. The pulse signal is the wire from the transmission to the speedometer. For the HU, there is just a wire that splices into it. I spiced into it behind the instrument cluster.

04-15-2006, 03:26 PM	#1 (permalink)
993K Registered User Join Date: Oct 2005 Trader Rating: (5)	Ground loop issue Okay, I am enjoying the ever popular alternator whine. I've read some of GMo's input on past problems to trouble shoot my issue. Here is what I have going on... I can have the stereo off (and even disconnect the power and ground to the amp) and the whine is still there (although not through the speakers). Could it be coming through the underdash speaker for the beepers for the door also? When everything is hooked up it is noticeable at no or low volumes or when there isn't much bass through the stereo speakers. Its frequency and pitch is in direct relationship to the rpms of the motor. Help! Its annoying the crap out of me!

04-15-2006, 04:23 PM	#2 (permalink)
streetracero1 Forum Member Join Date: Mar 2006 Location: vineland, nj Drives: 95 3000gt sl Trader Rating: (0)	Re: Ground loop issue yea that sound is a pain in the ass i've delt with it many times. i always find it best to just pull everything out and reinstall it all thats normally makes life easier for me to find the problem but not nessaceray. its normally because an rca is ran too close to a power wire so try that __________________

04-15-2006, 05:14 PM	#3 (permalink)
993K Registered User Join Date: Oct 2005 Trader Rating: (5)	Re: Ground loop issue Thanks for the input. I have the rca's running down teh opposite side of the car from the power wire so the only place they are close is by the amp. I made sure they were not close to each other and I still have the noise. Of course, I was figuring this...the noise existing with the factory system before I ever installed new speakers and the amp. However, now with it in the system, its amplified more. It was easier to deal with the stock system at this point... Anyone have any other ideas?

04-15-2006, 06:12 PM	#4 (permalink)
GMo SQ Junkie Join Date: Oct 2003 Location: Carrollwood, FL Drives: 95 3000gt SL Trader Rating: (1)	Re: Ground loop issue Alternator whine wouldn't be happening due to RCA's and power wires running too close with DC. So, you have the amp(s) disconnected from the signal (RCA's) and still have whine...can you pinpoint the source of the noise? Have you had problems with your alternator? Have you been having problems with your battery? I would have both of them tested if you can't figure this out, and I believe places like pepboys do it for free. You can use a multimeter or voltmeter on your battery to see if that's functioning correctly. Anything which outputs pulse width modulation (computers. lights, amps, HU) can be causing the alt whine . It can be heard through any speaker which doesn't have a high pass filter under the audible frequency. I've seen aftermarket alarms causing it. If your HU is still connected to a speaker it could be causing it. No matter what I would re-do your grounds, like I've previously explained. Check your battery for a proper voltage- whatever it's spec'd at , 12.6V or around there, and for a proper charging voltage, around 14V. If your battery is failing or cycled down, it could be the culprit. __________________ *Advances are made by answering questions. Discoveries are made by questioning answers.* -Bernhard Haisch

04-15-2006, 08:41 PM	#5 (permalink)
993K Registered User Join Date: Oct 2005 Trader Rating: (5)	Re: Ground loop issue Well, my car has been idling low intermittently when I'm sitting at a light (no tune up due) and I have notice the battery gauge reading a bit low from time to time lately as well... I didn't realize a low battery would cause the whine too. Wow, I hope that is it. I'm going to put it on the charger and see what happens (even if its a temp fix I can figure its time for a battery). I did all the ohm measurements with grounds like you previously stated and everything was looking okay. I do not have any speakers hooked to the head unit and no alarm. I do however have the speedometer pulse signal parallelled into the deck (it is a navigation unit that uses this signal for esimated positioning when the antenna cannot find a satelite (like when you are in a tunnel). I should disconnect that and see what happens. Well, the battery first...

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04-16-2006, 12:24 AM	#6 (permalink)
993K Registered User Join Date: Oct 2005 Trader Rating: (5)	Re: Ground loop issue Got the battery up to par again...no help with the noise. I haven't had any alternator problems but I guess I'll go have it tested. The more I think about the speed pulse, the more I figure that shouldn't effect things, right? It goes right into the HU and there are no speakers connected there...only RCA's.

04-16-2006, 11:05 AM	#8 (permalink)
993K Registered User Join Date: Oct 2005 Trader Rating: (5)	Re: Ground loop issue What do you mean disconnect all of the sources? All wires to the HU?

04-16-2006, 12:27 PM	#10 (permalink)
993K Registered User Join Date: Oct 2005 Trader Rating: (5)	Re: Ground loop issue The HU is grounded to the chassis. I only have 1 amp and a Sirius tuner that has grounds in the trunk (they do share it trhough a distribution block). Ohm readings seem to be okay there. The pulse signal is the wire from the transmission to the speedometer. For the HU, there is just a wire that splices into it. I spiced into it behind the instrument cluster.