Installed a New HU why are volts reading 12v on guage?

[APitBullT 10+ year member]

I just installed a new HU my buddy gave me, and the volt guage reads 12v when i reverse. but when i rev the engine in drive it goes back up. was my battery drained when i installed the deck?

also im hearing a low humming noise when the volume is at 0, and its very annoying, i checked the rca's but nothing is wrong there. what could this noise be?

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[djjdnap 10+ year member]

when in doubt check your ground(for the noise)

Also, about the 12v, not sure y it would read that, when you start your car it should charge back up, especially if you have a 260alt. Just let the car run for a while it should charge back up. or let autozone charge it for you.i think its free?

 

[APitBullT 10+ year member]

alright thanks bro

 

[Chevyaudio 5,000+ posts]

definatly check the ground for the noise problem.

 

[APitBullT 10+ year member]

which ground should i check? the HU OR AMP?

 

[jsloan10 10+ year member]

High output alternators have a tendency to need greater RPMs to develop their 14volts, one option to help this is to replace the belt pulley with a smaller one to increase its rmps when the motor is at idle.

As for the hum here is a complete guide for getting noise out of the system-

2 Electrical

*****************

This section describes various problems and concepts which are closely

related to electronics.

2.1 My speakers make this high-pitched whine which matches the engine's

RPMs. What is it, and how can I get rid of it? [iDB]

==========================================================================

The answer to this section was generously provided by David Navone of

Autosound 2000. The material in these instructions was adapted from

the Autosound 2000 Troubleshooting Flow Chart by Ian Bjorhovde with the

permission of Autosound 2000. For more information about Autosound

2000, (see Section 7).

This is a set of instructions to debug a stereo installation if there

is any noise present after it is completed. Follow each step

carefully! If you have more than one amplifier, repeat level one for

each amp to be sure that none of them are responsible for the noise.

2.1.1 Level 1: Check out the Amplifier(s)

------------------------------------------

After you have determined that there is noise in the system, determine

if the amplifier is causing the noise. To do this, mute the signal at

the inputs to the amp by using shorting plugs. If there is no noise,

then the amp is fine, and you can proceed to level 2. However, if

there is noise, then use a test speaker at the amp's output. If this

stops the noise, then the problem is originating in the speaker wiring,

or the passive crossovers. Check to make sure that none of these are

shorting with the body of the car, and start again at level 1. If

noise is still present when using the test speaker, then there may be a

problem with the power supply on the amp. Try connecting an isolated

power supply - if this does not get rid of the noise, then there is

something seriously wrong with the amp, and it should be replaced. If

the noise goes away, then there may be a problem with power supply

filtering or isolation. This can be fixed by changing the amp's ground

point or b adding external supply filtering.

2.1.2 Level 2: Reduce the System

---------------------------------

The amps have been determined to be noise free. If you have any

processors between the head unit and the amps, disconnect them and

connect the head unit directly to the amp. If this gets rid of the

noise, then one (or more) of the processors must be at fault, so

proceed to level 5. Otherwise, try running the signal cables over a

number of different routes. If you are able to find one that does not

produce any noise, permanently route the cables in the same manner, and

proceed to level 5. If not, then you must isolate the head unit from

the car's chassis (except for its ground!) - don't forget to disconnect

the antenna, since it is also grounded to the car. If isolating

the head unit does not solve the problem, the move the grounding point

of the head unit. Hopefully the noise will be gone, and you can

install the head unit with a quiet ground and proceed to level 5,

otherwise go on to level 3.

2.1.3 Level 3: Move the Head Unit

----------------------------------

The amplifiers are fine, but moving both the ground for the head unit

and the signal cables does not solve the noise problem. Take the unit

completely out of the dash, and put it on either the seat or carpet,

and run new signal cables to the input of the amp. If this solves the

problem, re-install the head unit, one step at a time and skip to level

5. But if the noise persists, then move the head unit as close to the

amp as possible and use the shortest possible signal cables. This will

verify that the original signal cables are not causing the problem -

assuming the noise is gone, reinstall the head unit one step at a time

and go to level 5. Otherwise, there may be a problem with the power

filtering for the head unit. As with the amps, power the head unit

with an isolated power supply (again making sure that the head unit

isn't touching the car's chassis at all). If the noise goes away, you

can add power supply filtering or an isolated power supply; go to

level 2. But if the isolated power supply does not solve the problem,

then you can either replace the head unit and go to level 2, or check

the car's electrical system in level 4.

2.1.4 Level 4: Testing the Car

-------------------------------

There does not seem to be a problem with either the head unit or the

amplifier, and the car's charging system is suspect. To see if this is

the case, we can use a system in a car that is already known to be

"quiet." Bring both cars together as if you were going to jump one,

and use jumper cables to connect the two batteries. Start the engine

of the car with the noise problem, and listen to the "quiet" car's

system. If the noise does not go away, there is a SERIOUS problem with

your car's electrical system (possibly a bad alternator). Have a

qualified mechanic check the charging system out. If there is no noise

in the "quiet" car, then the "noisy" car's charging system is

definitely quiet, so continue with level 5.

2.1.5 Level 5: Adding Signal Processors

-----------------------------------------

We have proven that the amplifiers are good, the head unit is good, and

the car's electrical system is good. Now we need to reconnect each

signal processor. Repeat this level for each signal processor used in

your system; if you have added all of your signal processors, and

there is no longer any noise, CONGRATULATIONS! You've removed the

noise from your system! Connect the signal processor. If there

isn't any noise, then go on to the next signal processor. Otherwise,

try re-routing the signal cables. If this cures the problem, the route

them permanently over the quiet path, and install the next processor.

If not, then isolate the processor from the car's chassis except for a

single grounding point. If this works, then permanently isolate the

processor, and move on to the next processor. If isolation does not

help, then advance to level 6.

2.1.6 Level 6: Processor Isolation Tests

------------------------------------------

Now, noise enters the system when one particular processor is

installed, but regrounding it does not help. Move the processor very

close to the amp, and check for noise again. If there isn't any, then

re-install the processor, carefully routing the cables to ensure no

noise, and continue at level 5 with the next processor. Otherwise, use

an isolated power supply to power the processor, making sure that no

part of the processor is touching the car's chassis. If this solves

the problem, the consider permanently installing an isolated power

supply or possibly a 1:1 transformer, and go to level 5 with the next

processor. Otherwise, separate the processor and isolated power supply

from the car by many feet and re- test. If there is still noise, then

there is a serious problem with the processor's design. Get a

different processor, and continue at level 5 with it. If separating

the power supply and processor from the car does solve the noise

problem, then either the processor is damaged, or your tests were

inaccurate. Repeat level 5.

 

[djjdnap 10+ year member]

making a smaller pully for low rpms is nice, but think about when you do 80 on the highway, can you say fried system.

 

[jsloan10 10+ year member]

Thats why they have voltage regulator built into them.. //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif