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Thread: power problems while car is running..

  1. #1
    Constant Bitrate
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    Feb 2000
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    AZ
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    Post power problems while car is running..

    To start off, ill explain the setup:
    I have a 12gauge direct connection to battery, rocker switch mounted in dash between battery/12v dc outlet, then from there it goes to the 12vdc outlet in trunk, then from there to my portawattz 140watt dc/ac inverter. The outlet is grounded, switch is grounded.. all should be good.. now,
    I have a computer in trunk for music (ya im cheap, dont wanna buy a mp3 player so made it).. it will currently only run when car is OFF. If i turn car on, then try to turn on computer i get a fault light from the inverter. But i can turn it on when the cars not running and itll work fine. Computer power supply grounded, i am totally lost on whats causing it to fail when the car is running. I have a pretty new alternator (somewhere around 70amps SHOULD be no problem for this car (its a small 4dr/4cyl/4spd/4pass yes! its a 4x4! costed me $180 a few months ago..) so alternator shouldnt be problem... the battery is one year old, a Les Schwab XHD 5 year battery, constant voltage around 12.68 with everything (lights, ac, defrost, ect) running... 12.75 when nothings running.
    Get a rock solid 15volts when car is on, 1/3 throttle gives me 17volts.. I hit switch for computer and inverter faults, but the voltage doesnt drop.. this has me thinking the need for a cap is eliminated since its not a drop in voltage causing it..
    Also, if it makes a difference, the inverter itself does run when car is on (right now i have computer and a 3 piece speaker setup on the 140watt inverter. (no its not overloaded, cause it works fine if car is not running).. the speakers come on with inverter, but when i hit switch for computer to come on the inverter faults. Im confused!! Help! (i doubt its my alternator cause this one is a R/V duty alt.. should handle fifteen times as much.
    Thanks for any help
    -im kinda mad cause all i need is an AIWA or another good head unit with either rca or miniplug input (i aleady have coaxial audio ran from trunk to right beside my current blaupunkt rpd435 (can you believe they still sell these things for $160?!?! i bought mine nearly 2 years ago for $140 !! and they sell for $160 new now! haha.
    ANyways i am almost done, just that it wont run while car is running.

    Tim
    99 ram 5.9 turbo
    P4 2.0, MicroATX, Audigy2nx, Monster Cable / Alpine.
    Coming soon: Indash motorized, 5.1, dvdrw, gps, bluetooth, wifi, and more!

  2. #2
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    New Concord, OH, USA
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    Post

    Sounds to me like you are getting too much voltage when the car is running. 15-17 volts may be triping the fault on the inverter. I'm not an expert so what does everyone else think.

  3. #3
    Maximum Bitrate
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    Nov 1999
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    Thats right that voltage is way too high
    the max volatge altinator should supply is not more than 14v
    Well now its clear why your inverter goes in to protection mode , cos the input voltage is way to high. Check the regulator of the altinator if its external or even better see an autoelectrition.


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

    Fosgate
    Fosgate

    System Comp V3 - In progress.
    Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.

  4. #4
    Constant Bitrate
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    If its not suppose to be this high then why do some car audio amps require 14.4+ volts? There are even some taht want 16volts. I just sorta half-@$$ed fixed the problem. (not really but i found a way to get it to work).. After trying to hardwire the inverter tothe battery, i turned the inveter on, then not even a seocnd later hit the computer switch and it works (what happens is before the inverter protects itself and "arms" its protection, the computer has already got the voltage surge it needs to startup and is running.
    I only have one problem left, and that is: healights, defrost, heater, airconditioning. If I have computer running, then turn on either one of those, the inverter faults. This isnt much of a problem, as if i were to go driving at night id simply turn on my lights before the computer.. or if a long trip, simply shut down computer, turn on lights, then startup again.. only takes about 35seconds total to shutdown and startup again anyway. NOt too much of a hassle but it has me worried a bit about the cars cheap electrical system.. Im gonna buy new battery cables in a week or so anyway cause ive found some corrosion on the inside of the wires from where it entered the ends and worked its way inward.. so that could be a problem too, not enough juice can flow through them

    TIMMMM
    99 ram 5.9 turbo
    P4 2.0, MicroATX, Audigy2nx, Monster Cable / Alpine.
    Coming soon: Indash motorized, 5.1, dvdrw, gps, bluetooth, wifi, and more!

  5. #5
    Constant Bitrate
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    Post

    I'm not much of an electrical person, but can't you just plug your inverter into some sort of voltage regulator?

  6. #6
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    Post

    17 volts is far too high. 14.6 should be the maximum you ever see. The regulator on your alternator is shot. Save your equipment and get it repaired.

  7. #7
    Constant Bitrate
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    14.6 is the max i should see?? i checked voltages on otehr cars here and they are almost the same. 92 blazer = 16.7volts 88 lesabre = 15.9 volts 86 ram 50 = 17.3 volts. The 86ram has high voltage caues it also ahs a new alternator in it to handle higher audio loads (bro's truck)... blazer has 16.7 cause it had something electrical done to it to support new fog lights... and lesabre is just stock.

    That mean every single alternator is shot? dont think so...

    Anyways, i figured out how to get it to run.. i just have to hit the computer switch real fast after the inverter switch so the computer gets its surge of poewr before the inverter gets a chance to "arm" its protection.

    TIm
    99 ram 5.9 turbo
    P4 2.0, MicroATX, Audigy2nx, Monster Cable / Alpine.
    Coming soon: Indash motorized, 5.1, dvdrw, gps, bluetooth, wifi, and more!

  8. #8
    Maximum Bitrate
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    Mate whatever you using to check the voltages is not mesuring correctly.
    14.1 is that max you should get with any car ok. I been working with cars for well over 3 years doing autoelectrition/stereo installations. And trust me there is no way on earth that altinator can give out more than 14v if the regulator is working. I guess u know whats is regulator mean and does... So either its your multimeter is stuffed or you not mesuring it correctly!
    Use some other multimeter to take the mesurments and expect something in the range of 13-14v.


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

    Fosgate
    Fosgate

    System Comp V3 - In progress.
    Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.

  9. #9
    Newbie
    Join Date
    Apr 2000
    Posts
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    Post

    You must also consider the cell voltage ratings of the battery...
    17 volts would boil a battery completely dry in a matter of hours. Given the large error in readings you are getting, i'd say your multimeter is history. I run a Fluke 87.
    $350 new, well worth it. Further, i admittedly made a typo in the previous message. 13.6 is nominal voltage. It can peak as high as 14.2 during the initial surge after starting the vehicle, or after any type of major surge. If it runs higher, it may indicate bad cell(s) or problem with the charging system.


  10. #10
    Newbie
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    Apr 2000
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    TimW and the group,
    Please visit the following URL: http://www.ee.ualberta.ca/~schmaus/batfaq.html

    It's highly informative material that all
    of us "gear heads" should know. Good stuff.


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