Loud Humm Through Speakers
 

OK just finished a painless kit on my sons 71 chevy. We were going through the testing procedure where you hook a 10 amp battery charger to the system but we are getting a loud humm through his speakers everytime we power something off i.e. headlights and fan switch? Any Ideas? Oh yeah the deck is brand new also, but no amps just a head unit and four speakers. Thanks in advance for your help!!!

Re: Loud Humm Through Speakers
 

check that you have good grounds you can also reverse the polarity of the speakers and see if that helps

Re: Loud Humm Through Speakers
 

Forgot to mention that it even happens when the radio is powered off. It kind of sounds like when a microphone goes haywire when soeone get to close to it.

Re: Loud Humm Through Speakers
 

is it a high pitch squeal? if so, that is direct short somewhere. time to break out the voltage meter....

Re: Loud Humm Through Speakers
 

Its more like a bass hummmmmm.

Re: Loud Humm Through Speakers
 

a bass hum, interesting. with the ignition off, correct. are you running any type of motorized devices on ignition, like an electric fuel pump or electric fans (cooling, etc?)

is the head unit new or from before you rewired?

Re: Loud Humm Through Speakers
 

head unit is new, nope the harness had wires for all that stuff but we just crimped them off?

Re: Loud Humm Through Speakers
 

we turned the headlights on and every thing was fine. The loud humm seems to happened when we power something off, I also forgot to mention hummm is also present with the key switched to accessory, but it is very faint.

Re: Loud Humm Through Speakers
 

that is an interesting one. in my 20 some odd years of installing, I've never heard of that one.

can you try to run a secondary ground? sounds like when the lights are activated, the chassis ground strengthens somewhat. I still think it's a faulty ground. are you running the stock ground through the original wire harness?

sorry for all the questions, but it's one of those "not so easy to answer" questions! :lol:

Re: Loud Humm Through Speakers
 

No problem at all thanks for all your help. The ground on the head unit harness is grounded to the dash right now, should I try to run it to the chassis. It also happens when we turn off the fan switch.

Re: Loud Humm Through Speakers
 

one other quick point we didnt use the brace for the back of the unit because it was kind of cramped does the brace serve as a secondary ground???

Re: Loud Humm Through Speakers
 

I don't know how many head units I installed over the years that didn't have a rear brace. short of jumping speed bumps daily, I never use the rear mount brackets. they are a pain in the butt. however they are a GREAT theft deterents!!! the braces should in no way be a part of a secondary ground connection.

I'd try running a ground directly to the chassis. your ground connection for the headlamps and heater fan are tied directly to the chassis/frame.

give that a whirl and report your findings.

Re: Loud Humm Through Speakers
 

good stuff I'll try that and get back to ya either way thanks again!!

Re: Loud Humm Through Speakers
 

Something is sending a signal to the chassis. Take the battery charger off and see what happens. We have a similar issue in my dad's '06 except we get digital tones through the speakers. While the truck is off. Weird right?

Re: Loud Humm Through Speakers
 

is the charger an automatic type ,that may ajust amps as needed ,may be noise from the charger? try with a batt if you can, does the truck or did the truck ground the one side of the speaker before?? new radios don't ground out one side anymore ,make sure only the power ground is grounded not speakers

Re: Loud Humm Through Speakers
 

I am using the battery charger to make sure there aren't any shorts in the newly installed harness before connecting a battery. I was sort of thinking along your lines motornut, that the charger might have something to do with it because it only happens when I power stuff off. The main thing keeping me from hookin the battery up is that this happens even when the stereo is off?????? I know the radio has both switched and constant power, just a little worried I'm gonna burn the whole damn thing down lol. The stereo and all speakers sound good when its powered on and nothing else is messed with. Am I risking screwing something up if I connect the battery?

Re: Loud Humm Through Speakers
 

the verdict is finally in, it was the battery charger i was using to check the system out, once the battery was hooked up everything worked like a charm. thaks so much for all ur heklp and input! :smoke:

Re: Loud Humm Through Speakers
 

Just for reference, most battery chargers overcharge when connected with out the load from the battery. Ive seen as high as 16VDC on some of them. Most electrical systems are somewhat tolerant of this, but some are not and the results can be disasterous. Glad you got the issue solved tho. Have fun