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456 posts

Ultimate Geek


# 140976 25-Feb-2014 21:07
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So last week I installed a new head unit and sub woofer (and amp) in the boot of my 96' Toyota Caldina.

The install went well, and everything worked fine, until yesterday (about 6-7 days after install) the car failed to start.

After a jump start, the car ran fine. Then this morning (25th), the car failed to start again. After a jump start it got me to the place I needed, and then without turning the car off it got me home again. And (not) to my surprise it failed to start yet again this afternoon.

After doing some reading online I think I've narrowed down the issue to poor choice of grounds for either my head unit and/or the amp in the boot. Apparently a poor ground will cause the battery to not get charged properly which explains why it took nearly a week for the issue to actually become noticeable.

I've already checked all my wiring to ensure I've connected the constant 12v+ and the ignition operated 12v+ the correct way around as this can cause battery drainage. However a "drainage" issue wouldn't explain my situation as it took nearly a week for the battery to "die". And now it's "dead" it won't go back to 'full" again. I also tested the alternator to ensure it was giving a constant voltage of about 14.3-5 volts, which it is.

Tonight, I've disconnected both the head unit and amp's 12v+ and ground cables, and jumped the car and "charged" it for over half an hour. The battery now gives a steady 12.5 volts or so, when the car is off. And the car seems to start okay tonight.

My plan is, to see if it starts fine tomorrow, which if it does, concludes either one of my grounds is the issue in which case, my main question leads in:

How should I ground my after market equipment? I had the amp grounded to an existing ground bolt, that the boot's cigarette charger was connected to. It had a lead that went of behind the car panel's somewhere. I presume this is a factory installed "ground". And the head unit was attacked to some metal frame behind the dash, which was easily accessible. Is there any way I can easily find out which grounds are suitable or not?

I have an easily accessible alternative ground for the amp (the bolt's/frame under the boot's carpet holding the rear seats), if I need, but an alternative ground for the head unit would be more of an issue. I'm aware the point of ground connection needs to be free of paint, or any coating. Also the battery is only about two months old, so "shouldn't" be the issue.

Any help, comments or advice on this situation would be much appreciated!

Thanks,
-A.

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19282 posts

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  # 994444 25-Feb-2014 21:11
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How did you charge the car battery for 30 minutes? Hope you don't think the car alternator is going to do this,

First off charge the car battery for 24 hours on a bench charger then get it load tested with a CCA meter

John



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Ultimate Geek


  # 994446 25-Feb-2014 21:13
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johnr: How did you charge the car battery for 30 minutes? Hope you don't think the car alternator is going to do this,

First off charge the car battery for 24 hours on a bench charger then get it load tested with a CCA meter

John


30 minutes from the alternator should be enough to charge it to the point, that it could restart the car.

-A.

 
 
 
 


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  # 994448 25-Feb-2014 21:16
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AidanS:
johnr: How did you charge the car battery for 30 minutes? Hope you don't think the car alternator is going to do this,

First off charge the car battery for 24 hours on a bench charger then get it load tested with a CCA meter

John


30 minutes from the alternator should be enough to charge it to the point, that it could restart the car.

-A.


Not if the car battery is porked, Also something else make sure the fan belt is good and not cracked as extra load on the car alternator can cause it to slip under load and not charge,

Just cause you hear no squeel does not mean the fan belt is in good condition

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  # 994452 25-Feb-2014 21:18
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I worked in the car battery / electrical area for a number of years before VodafoneNZ



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Ultimate Geek


  # 994453 25-Feb-2014 21:23
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johnr: I worked in the car battery / electrical area for a number of years before VodafoneNZ


The only reason that the issue isn't related to my head unit/amp wiring would be of a very unlikely (and unfortunate) coincidence.

How would you suggest I ground my new equipment? I read somewhere that it's best to have all your grounds connected to the same place. So I am therefore assuming having my amp grounded to the "main" ground in the boot is a "better" option. Meaning that either that information is incorrect, or it's the head unit's somewhat makeshift ground causing the issues. I just don't see any other good place to ground the head unit, without running a wire from somewhere else.

Any suggestions?

-A.

Quick update, it's been about 3 hours since the car was last on and the battery maintained 12.7 volts while off and the car started flawlessly. Which is a huge improvement from last night's performance and implies that the "charge" from driving around earlier today has actually (partially) "charged" the battery this time (after disconnecting the new problem causing equipment). Which tells me, that unplugging the headunit and amp's 12v+ and grounds has fixed the issue of "blocking" the battery from being charged. Now all I need to do is find how to properly ground my equipment.

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  # 994457 25-Feb-2014 21:30
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Forget about how the radio / amp is earthed at this stage get the battery CCA tested, You can get it done free at many places for free




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Ultimate Geek


  # 994461 25-Feb-2014 21:34
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johnr: Forget about how the radio / amp is earthed at this stage get the battery CCA tested, You can get it done free at many places for free



The roadside assistance guy "tested" it this morning as said it was fine, right before he jumped it. I presume his "test" included CCA.

Cheers,
A.

 
 
 
 


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  # 994463 25-Feb-2014 21:38
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How can they perform a CCA test if you are getting a jump start? CCA test has to be done with the battery fully charged and if it was fully charged you would not be getting a jump start



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Ultimate Geek


  # 994464 25-Feb-2014 21:40
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johnr: How can they perform a CCA test if you are getting a jump start? CCA test has to be done with the battery fully charged and if it was fully charged you would not be getting a jump start


Oh, okay, that makes sense.

I'll see if the car starts tomorrow. If it does, then the issue is definitely related to my wiring. If it doesn't start, then the CCA test will be the next option.

Thanks for the help.

-A.

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  # 994466 25-Feb-2014 21:41
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You can never have enough earth... my 21 year old bmw has about 100... all over the place. There's a bolt under the back seat with about 30 just connected to it! Plus a dirty big earth strap on the other side. :D

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  # 994468 25-Feb-2014 21:44
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Does not prove much if the car starts tomorrow morning, For a start you need to get the car battery on a bench charger for 24 hours now as it's been drained enough to need a jump start,




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  # 994469 25-Feb-2014 21:45
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The ground connection only affects noise, not charging. A star connection is simply to avoid ground loops and voltage drops across ground connections.

There is a thin wire to the amp to turn the amp on/off with the ignition turning on/off. It is possible the amp is turned on all the time which will slowly drain the battery. As an example, a 40Ah battery needs only 0.25A to completely drain in less than 7 days.

In the process of installing, did you disconnect the battery? Perhaps dirt got in the terminal which prevents a proper connection, and perhaps when you did it again to disconnect the amp you also unknowingly got the dirt out?

Batteries do not like a fast charge from a deep discharged state. As John said, get a slow charger on it overnight. Car batteries also do not like to be in a partial state of charge.




You can never have enough Volvos!




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Ultimate Geek


  # 994471 25-Feb-2014 21:45
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blakamin: You can never have enough earth... my 21 year old bmw has about 100... all over the place. There's a bolt under the back seat with about 30 just connected to it! Plus a dirty big earth strap on the other side. :D


I'd hate to ask, what you've added to need all that? ;)

-A.

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  # 994481 25-Feb-2014 21:54
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First of all sort out any battery issues, beg, buy or borrow a car battery charger, fully charge the battery.

You will need to find a multimeter and test the amount of current draw by the amp and head unit while the keys are off, a typical standy by current drain should only be a few mA.

Next step to help with any grounding problems is check the voltage at the battery with the keys off, and again at the amp with the keys off, much difference, the greater the difference the poorer the connections, prefore the same test with the car running and the amp going cranking out a bit of power, you may need 2 meters at the same time, one at the battery, one at the amp, there will be dips in the voltage that correspond with the beat of the music, but if all is good both meters should read the same.

I suspect the standby current is the problem, maybe the remote turn on wire has been hooked up to +12V so the amp is always running even when the keys are off causing excess current drain, ideally this wire should be connected to the "remote turn on" from the head unit.

Greg

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  # 994483 25-Feb-2014 21:58
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AidanS:
blakamin: You can never have enough earth... my 21 year old bmw has about 100... all over the place. There's a bolt under the back seat with about 30 just connected to it! Plus a dirty big earth strap on the other side. :D


I'd hate to ask, what you've added to need all that? ;)

-A.


They're just the factory BMW ones! Mind you, when you've got electric & heated seats, auto everything, and a 10 speaker stereo system from the factory, they probably decided they needed them! :D

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