headlight hummmm

iworkfortweeter

my headlights are humming. coming thru all speakers exept the subs. i was thinking possibly the head unit wasn't grounded properly, but it may be something else entirely, i don't know...but the noise stops when i turn the lights off, so im pretty certain its them. haha, any ideas?

brettw22

****.....easy.....Drive during daylight.

KevinLWhitaker

As you mentioned try checking the ground. I would move the ground point around to see if that influenced the hum. Also, is everything grounded to the same point as the sub, if not, try a common point (if possible). Check to make sure nothing else, such as a screw, is grounding your equipment. Finally, check the routing of your cables, particularly rca, to make sure they are not near any type of component or relay, that could induce the hum. If you have other cables, try those or look at cables with more insulation.

Its really going to be a Sherlock Holmes/process of elimination to track down and eliminate the hum. I would test isolated parts of your set up to try and find which part is picking up the hum.

Kevin

iworkfortweeter

thanks kevin, i checked everything, including the grounds, etc, and am still experiencing this phenomena...i don't know too too much about mobile as i work in home installation, but i do believe that the RCA's are picking up the hum, thru the power wires or something like that...is there a way to ground the rca's? i have three pairs running to the trunk where all the equip. is...

KevinLWhitaker

I have never grounded my RCA's although I have seen them with metal wires at each end that I presume is for such a purpose. As you proposed I would begin with my amp grounds and try grounding them to a better and/or different point. I would also check all the components to make sure all are well grounded. I would look at the routing of all my wires and the RCA's and try moving those around to see if it affects the hum. Also, make sure there is no inadvertant cable (or component) to metal contact (check your wires for any chaffing). Does the hum occur with the engine running, engine off, or both? Does the hum change with varying engine RPMs? As I mentioned above, it is really a process of elimination. I will say my experience with most noise in the system has been resolved by improving my amp grounds, but I have also experienced noise when switching to a different spark plug in the vehicle. This was resolved with better / shorter RCA cables.

Kevin

neomagus00

if you're running passive crossovers, try physically turning them around in the air near their current mounting point - the components in the xover can pick up radiated noise

grounding the rcas, no go, but you can try rerouting them - maybe there's a noise source near their current route

Custom Jim

It could be an induced signal in the RCA or any other component in the system. I remember a few years back on a car that the dash lights didn't work and I was troubleshooting it and we found a blown transistor in the dash light dimmer controller. I asked the service tech how it worked and he is thinking the design does not vary the voltage down like on a lot of older cars with a rheostat but pulsed the voltage to the light so they would be bright or dim or anything in between. How he explained it was at full brightness the light is seeing a pulsed 12 volts let's say 20 times per second but when it is dimmer the 12 volts is pulsed only 5 times per second.
I would tend to think this pulsing would eminate out of the control box and through any wiring directly connected to it.
I would maybe try removing the radio from the dash to see what happens and then try another triple set of RCA's outside the car for testing. If the noise is gone with the radio out of the dash there is probably a hot spot behind the dash (like years ago with cassette players in ford trucks as the main power harness ran above the radio opening and the tape head would pick up noise). If it is still there with the radio out but not with new cables going to the amps outside the car then I would try rerouting the first set you installed in the vehicle.
Jim

Greg Peters

Another few things you could try:

If you mostly suspect your RCAs, try a "twisted pair" RCA cable on one channel first and see if that solves the noise issue through that pair of speakers. The twisted pair RCAs are supposedly better at rejecting induced noise than the traditional type of cables. These cost a bit more, but maybe someone in the car audio install dept. at work might loan one for trial purposes.

If you are using a wiring harness kit between your head unit and the factory radio wiring, you might consider running separate, larger guage +12V and ground wires to your head unit rather than using those that run through the factory wiring harness. With some stereo equipment, you can pick up some noise from other electronics behind the dash that factory wiring runs in proximity to. While this noise may not have been apparent with factory radio, most aftermarket head units offer higher performance but can also amplify induced noise as well.

If the hum changes in pitch depending on engine RPM (even though only apparent with your headlights on) it may be that the additional load on the charging system when headlights are on is overtaxing your alternator, and it is actually alternator noise you are hearing. Aftermarket HID lighting and even high output bulbs can draw more current than some vehicles are designed for. Separate +12V wiring from your battery (or even fuse block) to h/u with a separate chassis ground may eliminate this, provided your alternator is able to meet the demands of all vehicle accessories plus stereo system.

Is the hum present in CD section as well as with am/fm tuner? If only present in tuner, it may be picking up noise through your antenna or power antenna wiring or connections, requiring some re-routing or shielding.

If your connections between the head unit and your amplifier come near the factory wire harness running along the inside your vehicle to the rear of the car, try running your stereo wiring down the opposite side of the car (or even the transmission tunnel) to isolate them. Isolate your large guage amplifier power wire from your RCA cables as well to minimize noise. Also, do not share system ground with one used by any vehicle accessory.

Good luck.

iworkfortweeter

the hum is actually only on when the headlights are on...i get a very slight alternator hum any other time, but im not too concerned about that...it makes my car sound a bit futuristic, i think! the headlights are annoying though, as when a cd changes a track and there is dead space on the disc, the noise really cuts thru. rca's are running to the trunk for the speaker and sub amps, and they are in fact radio hack cables, so maybe try some better ones? i really do think tho that it is a more serious problem, somehow a ground loop hum or something. getting an alpine cda 9857 to see if that resolves the hum perhaps eminating from the head end, i need a new one anyway, so what the hay. it really seems to be the lights though, and i have NO idea how to trace that problem...

KevinLWhitaker

It really sounds as if you have a grounding issue or a ground loop as you mentioned. Did you try working on your ground point for your amps? I would ensure the ground point is good (no paint, good metal contact) and if that did not help I would next try other ground points. Also, do you have multilple amps? If so try to see if the hum is isolated to one amp or all. Finally, as you mentioned, try some good RCAs. You may need to route them differently to eliminate noise. Do you have them rounted on one side of the vehicle and the power wires on the other?

As I mentioned before, its really a process of elimnation, but I would start with all your grounds. In the my experience, that is how noise is the system is resolved.

Kevin

exalted512

do you have amps on your highs or just your subs?
-Cody

iworkfortweeter

amps on EVERYTHING. absolutely every speaker is powered by an amp of some sort. is it possible that the system is just robbing too much power from the car itself? very occasionally the dash lights will flicker very slightly and get faster and faster until they become uniform and static, the light that is...another strange thing that's been goin on.. but you know...its so damn loud that i don't really even notice the noises its only when played a low volumes and headlights are on, or when no music is played and lights are on. if the headlights are off, all i get is alternator whine, but again, that's the least of my worries or so i hope:*)

exalted512

what deck do you have?

Do you know someone who has one with the same plug. Or do you know someone at tweeter thatll let you borrow one from the store just to plug it in to your existing one? That way you can count on it being the radio. If you have an extra pair of RCAs laying around someone, then unplug all your RCAs and plug in the extra and run it over the seats and plug it into one of your amps, see if it still makes the noise.
-Cody

MacLeod

Just for the record, the hum you get with the headlights on is the same alternator whine that you hear with them off. When you turn your headlights on it draws more from the alternator and there ya go.

Custom Jim has some good suggestions. If you unplug your RCA's from the amp and it stops then you know the problem is upstream of the amp.

exalted512

MacLeod wrote:

If you unplug your RCA's from the amp and it stops then you know the problem is upstream of the amp.

it could still be the inputs of the RCAs on the amp or the output of the speaker wire.
-Cody

MacLeod

If the amp is the culprit then it will continue to make the noise after the RCA's are disconnected, especially since its alternator whine and more than likely induced noise rather than a faulty piece of gear. If the noise stops then you know its being induced in the RCA's or eariler.

exalted512

wrong. If the inputs of the amp are bad, when you disconnect the RCAs, you will not get noise because there is nothing going into the amp. Same with the outputs being bad. If you disconnect the input, youre not going to get output.
-Cody

iworkfortweeter

well i figured it out. well, almost. i have a temp. fix anyway. you know that little gauge that lets you adjust the intensity of the bulbs behind your spedometer? well i was messing with that, and i always have it all the way down. very dim. well i turned it all the way UP and boom. no more noise. i know that its not a FIX per se, but as long as its not hurting anything, its ok with me, you know? so after months of trying to get technical solutions to my problem, its really just the simplest of things....
for now, ta

iworkfortweeter

ahhh.....................................quiet..........im just going to drive around for a couple of days and bask in the supreme wonderfull-ness of this.

Custom Jim

iworkfortweeter wrote:

very occasionally the dash lights will flicker very slightly and get faster and faster until they become uniform and static, the light that is...another strange thing that's been goin on.. but you know...

well i figured it out. well, almost. i have a temp. fix anyway. you know that little gauge that lets you adjust the intensity of the bulbs behind your spedometer? well i was messing with that, and i always have it all the way down. very dim. well i turned it all the way UP and boom. no more noise. i know that its not a FIX per se, but as long as its not hurting anything, its ok with me, you know? so after months of trying to get technical solutions to my problem, its really just the simplest of things..

This is why I'm thinking the noise could be eminating from the dash dimmer circuitry like from my original post (pulses the voltage 5 times per second to have the dash lights dim and 20 times per second to have them full brightness).
It might be from something close to this box or any of the dash light or ground wires or the lights themselves.

It might not be any wiring problem but a routing problem due to an induced signal. Granted some RCA's are shielded better than others but it might just be needing the slightest weak point on that shield (like on the round barrel ends) that it is getting into the system. It could also be from an unshielded area on the radio case. You could also have a bad dimmer as it flickers now and then with the music but this could be an electrical problem or a vibration problem being transfered to the dimmer control assembly.

Isn't troubleshooting fun .

Jim

iworkfortweeter

well look who was right.