Alternator whine through speakers?

Roboplex

Registered User
So as I'm driving my 90' SC for the first time, I realized that it has a really high pitched ringing sound through the speakers. It gets worse when the revs are higher. The car came with an old aftermarket Denon head unit in which you can remove the faceplate (and in turn powering off the sound) with a button. When I took the faceplate off, the whine stopped. I assume it's alternator whine. But I'm not sure where the culprit of letting it through is. Is it the head unit since it goes away when it's unplugged? Or is that just breaking the circuit, stopping the whine? I'd like some advice. Oh and I do have the JBL premium sound if that matters. Have you guys ever had this happen before?

Thanks :)
 
your head unit needs a better ground, any time ive had that sound(lol i called it my honda turbo) tt was fixed by grounding the stereo better or insulate the remote wire as its picking up the interference
 
Have you guys ever had this happen before?

Might be the head unit, might be speaker wiring (I've got one right now that is related to my subs but it hums when the head unit is off).

Is the small ignition choke filter/capacitor still on the coil?
 
your head unit needs a better ground, any time ive had that sound(lol i called it my honda turbo) tt was fixed by grounding the stereo better or insulate the remote wire as its picking up the interference
I actually thought it was the supercharger at first since I've never driven in a car with one before, but narrowed it down to the speakers.
 
I was thinking about installing one of those filters that will limit the alternator noise. Has anyone used them before? Would it help?
 
Might be the head unit, might be speaker wiring (I've got one right now that is related to my subs but it hums when the head unit is off).

Is the small ignition choke filter/capacitor still on the coil?
Sorry I know I probably sound like a complete idiot, but this is my first time dealing with car audio, so can you elaborate a bit for me xD? I'm not quite sure what you mean:confused:
 
Yes, the filter will help. Repairing the ground wire to reduce the ground loop will also help and should be the best fix. You might want to take a photo of the wire job so we can see if its been done right or if it's "Kustom".
 
Sorry I know I probably sound like a complete idiot, but this is my first time dealing with car audio, so can you elaborate a bit for me xD? I'm not quite sure what you mean:confused:

In that case, you might want to get to an audio shop and let them take over.
 
I actually thought it was the supercharger at first since I've never driven in a car with one before, but narrowed it down to the speakers.

Well, if you could hear the supercharger through the stereo, I'd say turn it up! ;)
 
Might be the head unit, might be speaker wiring (I've got one right now that is related to my subs but it hums when the head unit is off).

Is the small ignition choke filter/capacitor still on the coil?

My 90 also had a cap integrated into the alternator wiring, as well as the fuel pump ground.
 
So I might just replace the headunit. Not because of the whine nessecarilly, but because the Ford CD player doesn't connect to it and I'm stuck with tapes *shudders*, its older than god, and the volume knob quit working. As I'm trying to fix the knob to no avail, I noticed some corrosion on the PCB. Could that cause the whining? I know its a dumb question, but you never know. Any suggestions on a new headunit? Also, is the car wired with RCA cables? I know a lot of newer headunits only have RCA outputs and I don't want to buy the wrong one xD.
 
Corrosion, cold solder joints, blown capacitors...age takes it's toll. Did the Denon install include proper wiring or is there black tape everywhere?

No RCAs...all proprietary to Ford back then, except the antenna.

www.scosche.com sells adapters do deal with that (and the Denon already being installed may have already necessitated them), but know there isn't a ton of space in the radio bucket, so... Also note that they sell an adapter for the sub/amp harness in the trunk to provide connections out to the speaker harnesses (and again, the Denon install may have included that harness). See 35th.org/radio for wiring details if you don't have an EVTM.

I run a Jensen single DIN with DVD, pop-up LCD, nav, handsfree phone, USB, SD, etc., etc. Put an Alpine single DIN speaker in the lower hole w/double 10" subs in the trunk for 5.1
 
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Corrosion, cold solder joints, blown capacitors...age takes it's toll. Did the Denon install include proper wiring or is there black tape everywhere?

No RCAs...all proprietary to Ford back then, except the antenna.

www.scosche.com sells adapters do deal with that (and the Denon already being installed may have already necessitated them), but know there isn't a ton of space in the radio bucket, so... Also note that they sell an adapter for the sub/amp harness in the trunk to provide connections out to the speaker harnesses (and again, the Denon install may have included that harness). See 35th.org/radio for wiring details if you don't have an EVTM.

I run a Jensen single DIN with DVD, pop-up LCD, nav, handsfree phone, USB, SD, etc., etc. Put an Alpine single DIN speaker in the lower hole w/double 10" subs in the trunk for 5.1

Nope the Denon has RCA cables on it, but its only connected with the regular audio cables via a ford wiring harness/adapter. I don't think space will be too much of an issue, my VMM isn't functional atm so I could just shove the adapter in the empty slot and put the cover on for now. I also think my sub has blown, it rattles pretty bad when there's a good amount of bass. But that fix is down the line since I'm on limited funds at the moment.

Again, thanks for everything. You've been a huge help, and you sure sound like you know what you're talking about xD. I guess I'll let you know when I've found a new head unit to get your seal of approval ;).
 
I have fixed interference problems by replacing the amplifier on vehicles before. Not sure which factory system is on your car, but I believe you will find either a amplifier or radio issue as your culprit. If you have a separate amplifier, replace that first.

Chris Homan
 
Nope the Denon has RCA cables on it, but its only connected with the regular audio cables via a ford wiring harness/adapter. I don't think space will be too much of an issue, my VMM isn't functional atm so I could just shove the adapter in the empty slot and put the cover on for now. I also think my sub has blown, it rattles pretty bad when there's a good amount of bass. But that fix is down the line since I'm on limited funds at the moment.

Again, thanks for everything. You've been a huge help, and you sure sound like you know what you're talking about xD. I guess I'll let you know when I've found a new head unit to get your seal of approval ;).

Just a thought - the stock Ford radio has a separate chassis ground. Is there any provision for that on the Denon? If so, you might try hooking it up to the stock Ford spade terminal. (I would make an adapter from a short bit of wire and a male spade terminal, plus whatever terminal the Denon might take.)
 
Yes, the filter will help. Repairing the ground wire to reduce the ground loop will also help and should be the best fix. You might want to take a photo of the wire job so we can see if its been done right or if it's "Kustom".

So I'm going to try at least, to replace the ground wire, if the new headunit doesn't fix it. Like I said, the Denon headunit is just toast. But I'm not sure how to run the wire. Like, how do I run it to the chassis? Can you maybe walk me through the process :eek:?
 
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I have fixed interference problems by replacing the amplifier on vehicles before. Not sure which factory system is on your car, but I believe you will find either a amplifier or radio issue as your culprit. If you have a separate amplifier, replace that first.

Chris Homan

I've got the JBL Premium stock amp. Troubleshooting that is down the line if the other fixes don't work as I don't have another amp on hand.
 
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