70sgeek

Ok, somewhat of a backwards question but the issue is - I have engine whine (varies in sync with engine speed) feeding back through my aftermarket stereo (Custom Autosound USA-740) - just a radio and 4 speakers, no amp or sub. I've grounded everything as well as possible and even added noise filters (a Newmar 150 amp filter under hood between battery and alternator as well as a Custom Autosound inline noise filter inline to the radio power wire under dash).

For the most part engine whine feedback is practically indiscernible during non-headlamp use periods, but highly noticeable when lights on. I installed all new M&H harnesses within the last few years - headlamp, engine, batt cables, dash, intermediate and rear, so there's essentially no old wiring in the car. Grounded the battery to clean chassis mount, also added new engine strap.

It does increase appreciably however when I plug an MP3 player into the radio.

Alternator is a 3 year old Powermaster 100 amp (p/n 8002) internal regulator unit, and until recently it fed an Optima Red battery (which may be an integral detail here). I do note that when I pull the plug off it, the engine noise feedback is still present through the radio.

typically these issues can be rooted in poor grounding but I feel like I've exhausted that possibility from endless hours of tracing and retracing my install steps (I'm not a novice at stereo installs and general wiring). But over the last 2 years, I strangely went through 2 Optima batteries, each exhibiting dead-cell characteristics (failing to hold charges and essentially weakening to point of insufficient start power within 3 days of non-use, completely dead by week's end). At first I thought there was a parasitic drain sucking battery power but I couldn't find one.

so about 2 months ago I installed a new Duralast Gold battery and that solved the power loss issue, appearing to confirm the Optimas both went bad (though I don't know why). I have no current drain issues even after car sits dormant for well over a week. But I now wonder if the alternator may have caused their problems or itself have been damaged by these compromised batteries and is now the residual issue causing all the electrical feedback,. It seems to test ok in the car on my meter showing a 14.2 or so charge with engine running, but notably, turning lights on + any other substantive accessory (including brake lights), causes at least a 1 volt power drop (no dimming of lights or pop noises though).

So now I'm wondering if I install headlight relays (such as the MAD Electrical kits) will that cure the voltage drop and eliminate the increased noise feedback problem, assuming swapping another alternator in doesn't change anything by more direct means? I'm running Wagner halogen low beams and regular non-halogen high-beams), new (NOS) GM headlight switch and new aftermarket floor dimmer switch.

Are there any plug-and-play 4-lamp adapter harnesses for non-H4 type lamp systems that would save me all the cut and paste wiring modifications the MAD kits appear to require?

other thoughts / potential similar experiences and suggested fixes?

thanks

Fun71

The last time I had that type of whine in the radio (1980s maybe?) was due to a failing alternator, but you say the noise is still there when you disconnect the alternator, so it seems to rule that out. I can't think of anything other than the alternator that would induce whine into the electrical system.

Oh yeah, I just remembered I had an issue with a Custom Autosound radio that made a lot of noise. Sent that junk back and put my 1980s vintage Concord unit back in and cleared that up.

oldcutlass

Are you sure its not ignition noise that your hearing?

70sgeek

No feedback noise with engine off prior to changing out the last Optima battery, but I'll check that again with and without the headlights switched on.

I've moved the radio harness wires around a couple of times, to my immediate recollection they're not running in proximity to the headlight switch. I do have kick panel speakers with 14g wires coming up into the dash but they're not in physical contact with the switch either. may be another thing to recheck though..

I'm actually running a chassis-grounded wire into the dash to which the radio (-) is attached, in addition to the radio body bracket mount being bolted directly to the metal dash shell.

I do think this radio is unusually sensitive to electrical interference, presumably a brand issue.. It even reacted negatively to the shielded tach wire (volume used to intermittently suffer dropout issues until I rerouted the tach lead all the way across the right side of the dash to exit out just under the coil)..

70sgeek

Yes, increased noise with headlamps fully engaged.

I have the windshield-embedded antenna so I've never given that much thought as a potential culprit, worth re-checking though.

I'm mostly using the radio as an AUX source for my console mounted Sirius tuner (which I've thus far ruled out as being any part of the problem, as it doesn't contribute any feedback through the radio)

If I turn only the Sirius tuner on, no feedback noise - only when the radio itself is turned on

70sgeek

I have to recheck whether any noise increase in the park position only - don't recall much if any increase until the headlights were activated but it's possible

70sgeek

The radio has a front-mounted input for the MP3, when I play that on AUX2 through the radio input, I get additional whine feedback. but the sirius tuner (Streamate series, I believe) itself doesn't appear to contribute any feedback

Even with tach unplugged, feedback noise present.

I have a spare 63 amp Bosch alternator which I believe is good, I'm going to swap in tomorrow just to see what happens

oldcutlass

Sirius radio has a separate antenna.

stellar

Disconnect the positive wire from the alternator and try it. The 8002 ia a one wire alt, so unplugging it makes no difference. It will charge with or without the plug.

70sgeek

I know the windshield has a built-in antenna lead coming off it, that is what's plugged into the radio - was not aware it had separate grounding straps though. I don't know if the windshield has ever been replaced before me but it's possible. I'll have to see if I can find anything like that under the dash..

I did unplug the alternator from the 2-wire plug up top, with no change in noise feedback, have not actually tried running the car with it fully disconnected from power though. Will try that and advise the result.

Olds64

You should consider using a ferrite choke for the power lead to the radio.


It would also be a good idea to bond the trunk and hood to body.


This is the same thing I plan to do to eliminate common mode interference on my 96 when I install my ham radio.

70sgeek

Tried those - no appreciable effect that I could ever tell

matt69olds

Put a bolt meter across the battery terminals, set the meter to read A/C volts. If there is more than a couple tenths volt A/C then the alternator has a bad diode.

if that tests good, go get a cheap antenna from the parts store and. plug it in. Make sure you use a jumper wire to ground the antenna to a good ground. If the noise is still there, you can rule out antenna noise.

Ignition noise tends to sound more like static, charging system noise is more like a whine. If the noise is whine, disconnect and insulate all the wires from the alternator.

I don’t know what your music tastes are, but if it’s current country “pop” rap, or almost anything in tendu, it may be your radio trying to tell you something. 😏

70sgeek

nope my taste runs everywhere from 40's big band through early post-Woodstock indie rock, so my ragtop is all smiles over the road in that sense!

I think my past meter tests were arguably skewed by the Optima issues I had, so I'm trying to find time to re-check them now with the new Duralast battery in place that is known good.

the whine issue stayed constant with the battery swap though.

Fun71

Norm, satellite radios do indeed have antennas, as do mobile phones. They are a different design and size than FM antennas as they are receiving a different (higher) frequency.

Satellite radio antennas:




Cel phone antenna:

70sgeek

Ok, finally had some time for additional poking and in short, completely unplugging the alternator power eliminated the engine whine.

AC test resulted in an approximate .016 v reading

also, (with alternator connected) activating the headlight switch even to the parking lights position intensifies the loudness level of the whine, though it does not increase any further going from parking lights to headlights.

Have not yet had a chance to swap another alternator in for comparison.

matt69olds

You have a leaky diode. The whine you are hearing is excessive A/C voltage.

70sgeek

That's the thought I'm leaning towards at this point, and I now have to wonder if it ultimately caused the past 2 Optima batteries to fail (in both cases they developed discharge issues).

will hopefully find time tomorrow for an alternator swap to further evaluate.

Fun71

Very common failure symptom; a leaky diode injects AC noise into the electrical system, and the noise increases with electrical load (as in headlights turned on) since the alternator starts working harder to support the laod.

70sgeek

The VR harness connector which plugs into the top of the alternator caused no change in the whine output when I unplugged it, but removing the power cable from the alternator (completely disconnecting it from the electrical system) is what totally eliminated the whine.

70sgeek

Ok, so back to square.... swapped in a brand new Powermaster p/n 8002 alternator this p.m. and absolutely no change in conditions - charging perfectly, but radio still whining away in sync with engine speed like before.

so ultimately it has to be something further inline towards the radio section. I now noticed when I unplug the Sirius tuner power cable the whine practically disappears, so I'm going to trace all my radio-related wiring back over the holiday and see if can isolate things further - though the Sirius plug doesn't look bad maybe I need to replace it to eliminate the possibility of it having developed an issue (would definitely rather have it be a plug issue than the tuner....).

70sgeek

didn't unplug the windshield antenna lead from radio yet but from what I can tell not broken or visibly compromised - I'll be crawling around underneath more tomorrow in the daylight - is there in fact a separate grounding lead for the windshield antenna, other than the plug itself which goes into the radio antenna connector?

70sgeek

I'll check for that first thing when I get back on it tomorrow. the windshield may be original to the car but if it's not, it does appear to be installed to factory fit quality so hopefully no surprises in that regard.

70sgeek

Radio is connected to original harness connector for factory radio. I just checked the ws, unless ground clip(s) mounted under bottom chrome trim, I don't see any

70sgeek

I spent some time back tracing my under-dash wiring to recheck connections and routing for any feedback issues. Ultimately came down to finding the Sirius power wiring harness was at least 90% of the issue - pulling it completely out of the mix eliminated the majority of my whine issue. No further change with the windshield antenna unplugged.

So I ran out to Best Buy and bought a replacement Sirius docking kit - after installing it, with just the radio on (in the AUX mode so there's no music playing) there is still some residual whine which is only really discernible at its highest volume levels. with the Sirius turned on and music playing, essentially indiscernible and now no more increase in the intensity with headlight switch activated.

Will likely keep the new alternator in place and hold the old one for a spare at this point - turns out I had BB reward points so the new $50 Sirius kit only cost me about $3.25 ! Still not done chasing the residual whine though - possibly still a ground issue somewhere even as all my wiring is newer.

Moving the shielded tach wire did in fact previously improve some of the interference issues I was having with the radio - the radio power/sound level used to intermittently blip (drop in level) under any conditions (i.e. with or without lights on, not pressing brakes, etc.) and shifting the wire completely away from the radio proximity appears to have cured that. I still think my CA stereo is unusually sensitive to electrical interference though don't know if it's inherent in their breed or just my dumb luck...

appreciate all the assist to date - I'm getting good info from all of it towards sorting this issue out and hopefully more of it will be resolved over the holiday break!

70sgeek

Very solid advice - I've typically tried to use reasonable care in running car audio wires but rarely encountered issues like I have this time around.

I also replaced all my harnesses a few years back with M&H repops, so no OEM stuff remain at this point.

In this case all I'm running is the head unit and 4 speakers. The last time I worked on troubleshooting the whine issue I ran a power lead from radio straight to battery, which changed nothing - but at that time I still had the Sirius installed inline and hadn't thought to target that as a potential problem.

I will likely rerun that test - radio to battery directly just to see if it jumps past the remaining whine interference. then as needed, I'l start scouting for a more dedicated power source away from the OEM radio dash connector.

at this point I'm going to retrace my grounding points to reaffirm they're clean and secure. I'll next run a new test ground wire from radio to some individual frame points to see if any change in the residual whining occurs.

.

70sgeek

So appears mission may be finally accomplished for the most part.

went back thru my associated radio wiring and fortified the ground for the port where Sirius now draws its power, to a frame mounting spot under the hood. That seems to have quieted things down some more to where the whine is just about imperceptible except if I turn the radio up full volume with no input playing (and there's no intensity increase with headlight switch on) - with tunes going, its essentially a non-issue and absolutely no whine from my external Mp3 player when plugged straight into the radio.

So I'm taking this as a win.

Much thanks for all who followed this mini-drama - not the worst gremlin I've ever tackled but close!

70sgeek

I will definitely stay on this some more as time allows - it's personal at this point to completely eliminate whatever's left of the residual whine, so I'll be revisiting my existing grounds some more over the holiday - I have a wide braided strap from block to firewall and the a frame ground wire coming off the battery ( - ), the radio is grounded to another point in the frame at this point so I know I'm pretty close.

cjsdad

Engine noise comes in two distinct flavors, alternator whine and ignition static. As has ben discussed in this thread already, vehicle grounding is just as important as the positive voltage circuits. If you have a bad chassis or engine ground, the voltage circuits will find inventive and creative ways to complete themselves But they can insinuate themselves into audio systems in a multitude of ways. The most common way is alternator whine generated through ground loops. If your antenna ground has a different electrical potential than the dashboard where the head unit is grounded, you have a ground loop. Your car has a STEEL body and frame which is not the best electrical conductor but it will do the job if used correctly. As Chief indicated, the entire car is a ground source but because of corrosion, work hardening or fatigue, and a few other age related problems, the ground potential at the rear of the vehicle can be very different than at the front.

That being said, if you have a good ground cable from the battery to the engine block and again from the engine to the firewall, you should have the necessary ground potential in the dash to be able to completely correct and get rid of your noise. Since you have a windshield antenna, that throws a whole new monkey into the pot though. The windshield antennas are directly behind your distributor which is the main cause of ignition static. There are some very basic things that need to be done to make sure you are able to get rid of ignition static. These steps may seem over simplistic but after 15 years of working in the stereo industry everything I mention can make a difference. Make sure your distributor cap is clean and crack free! This includes cleaning all carbon off of the internal posts of the cap! Clean it or replace it if it is even remotely dirty. Make sure the distributor hold-down clamp makes a good solid connection between the engine and the aluminum distributor. Make sure your spark plug wires are in good shape. The easiest way to do that is start the engine and open the hood at night or in a dark garage. If you see ANY arcing, replace the wires and plugs. Too much resistance in bad plugs can cause arcing even if the wires are good. Old and dry wires and boots can allow arcing instead of positive arcing inside the engine through the spark plugs. Older Corvettes can be an absolute nightmare to troubleshoot and remove ignition static because they have non-metalic hood and firewall. That is why the older ones have metal trays to contain the ignition wiring. Back to your windshield antenna. The stub that goes from the bottom of the windshield to the firewall is very short and should have two sheet metal screws securing it. You can remove the screws one at a time and use a scotch brite pad or soft wire brush to clean the metal stub that connects to the vehicle and the base of the screws and then replace them. I say a soft wire brush because you don't want to remove the original plating if it still exists. If it is completely rusted, use an aggressive wire brush to get down to clean metal. Without a good ground, the antenna will pick up ignition static just as well as a radio station. Typical fender-mounted antennas have spikes on the mounting pivots that are under the sheet metal to dig in and make a solid ground connection. Your windshield antenna does not, so the screw connections are doubly important.

Alternator whine can be a total beast to identify and resolve. The most basic steps are biblical, Cleanliness is next to Godliness! Your alternator mounting brackets and bolts need to make a good electrical connection as well as mechanical mounting connection. The alternator body is aluminum, the mounting bracket can be painted, rusty, steel, cast iron, or on newer vehicles, cast aluminum. Dis-similar metals make poor electrical bedfellows. Make sure they are clean! It is sometimes easier to put a grounding strap/cable between the alternator body and the engine block, bypassing the need for an electrical connection through all of the mounting hardware. Make sure your alternator charging wire connectors are tight and not frayed. If your charging lead cannot carry the full voltage AND amperage between the charging post and the battery, it will over heat and cause resistance which will in-turn cause the alternator to try and over charge the system. Leaking diodes can cause noise as mentioned previously. Alternators create AC voltage and the diodes are there to turn it into DC voltage. If they go bad, the only cure is to replace them, usually in the form of another alternator. Sometimes the whine can be cured with a capacitor, or "noise suppressor" but not very often and it is just a band-aid for a deeper problem.

Something that can often be overlooked and happens to even the most experienced stereo installer is speaker shorts. If your speaker positive OR negative wires become shorted to ground, it will cause noise. Again, it may seem over simplistic but make sure the speaker wires are isolated from the body of the car. It's that ground loop thing I mentioned earlier.

Hope all of this is helpful in finding and curing your noise problem.

70sgeek

All sage advice for sure - still wrangling with some holdout alternator whine noise but it's barely perceptible except at the loudest radio volume, so has not been nearly as noticeable in recent weeks.

All primary OEM harnesses are newer M&H replacements at this point including both battery cables. I do have a newer engine-to-firewall ground strap as well as some additional grounds running to the chassis. Have also installed some inline noise filter/ground loop isolators which appear to have helped (though I know these are ultimately band-aids instead of cures). I have a Sirius/XM tuner tied into my stereo head unit for primary listening, rarely listen to local radio in the car, but the windshield antenna is plugged in and I don't recall it having made any difference being unplugged (but it's been a while since I've rechecked that).

I do think part of the problem is the radio unit (Custom Auto Sound 740) is just unusually sensitive to electrical interference (i.e. poorly shielded electronics) - besides the residual whine, the volume level occasionally blips (intermittent drop), which I believe I've traced to electrical resonance from the shielded tach wire (which I've since re-routed across the right side of the car away from the radio body).. This rarely occurs anymore so not as much of an issue as it used to be when a much more frequent occurrence.

I'm continually adjusting the under-dash wiring housekeeping in effort to eliminate more of the issues. Improvements have followed but still not there yet

Fun71

The above made me think about painted engines and alternator bracket mounting - paint between the block and brackets will be bad for grounding.

no1oldsfan

I come from years and years of installing car stereos. Like professionally. Had some cars in Low Rider magazine etc. The number one issue with your problem is using the factory ground wire. Do Not use the factory ground wire. Give that radio and the sirius the same non factory ground. I am telling you it could be that simple. Dealt with it a million times.

Burd

Take a look a GM’s radio noise pamphlet. It lists all causes, fixes, and parts to use to fix. Bam.

cjsdad

Where were you working? I was in Bakersfield for 9 years, Bay area for 3, and Phoenix for another 3. Did Car Audio Nationals and other sound-Off competitions throughout the '80s and '90s.

no1oldsfan

Here in Denver until 88/89. Moved up near Eureka California then. Completely different scene. No real sound offs up there ha ha. They didn't even have cell phones up there at the time. I schooled them on car alarms also.

no1oldsfan

Did you fix your issue?

70sgeek

Still working on it - easily the most stubborn of any of my past project cars - but much improved over before to where it's only perceptible at near-highest radio volume. More grounding re-checks to follow probably this weekend.

no1oldsfan

Did you disconnect the factory grounds?