Accelerating cuts out amp?

Discussion in 'Car Stereo Amplifiers' started by jedijunk, Apr 29, 2006.

  1. jedijunk

    jedijunk Full Member

    I'm relatively new to car audio, and me and a few friends (who know a little more than me) just put in an amp and a sub in my '87 4Runner. Turns out that whenever I accelerate, the amp cuts out - the light actually goes out, so I guess that means it's off. After a few seconds of coasting, braking, or sitting at idle, and the amp turns back on.

    We eliminated poor grounding as a problem by grounding the amp to the negative node on the car battery. A multitester showed an increase in voltage when I pushed on the gas, and we're pretty sure that it's this voltage jump shutting the amp down.

    I've been told several things by people, such as: a simple device (resistor?) will even out the voltage. I have an alternator problem. Older cars tend to have higher voltages.

    I don't know what to believe, and don't really want to go over to a car audio place and get charged for something that I believe is simple!!!

    Thanks for any advice anyone can give!

    Teddy

    PS - I can provide model names/numbers if necessary - when I get home from work.
     
  2. aznboi3644

    aznboi3644 Full Member

    Wait. You guys grounded the amp to the battery under the hood?

    Well what kind of amp is it? What is the voltage jump that occurs when throttled?

    Oh and what kind of sub is it?
     
  3. jedijunk

    jedijunk Full Member

    3 10s, each reading MTX Audio
    Kenwood eXcelon KAC-X401M is the amp. (I can't find a manual online anywhere!)

    The story behind the grounding thing: the amp was grounded to bare metal on the frame of the car. My friend said that might not be a good enough ground, so he ran a cable to the negative end of the battery - I dunno - but it didn't work anyway, so it's back to being grounded on the frame.

    I'd also like to note that the cut-offs are sometimes more sensitive than others. Sometimes I can just touch the gas and it turns off, while other times I can accelerate very slowly and it'll be fine (but pour too much on, and it goes.)

    However, TWICE now, only twice, I've been able to go as fast as I want and it doesn't shut off. It lasts for one trip, and as soon as the ignition turns off, its back to shutting off with the accelerator.

    Thanks!

    Teddy

    PS - I'll go get fresh voltage readings from the battery shortly
     
  4. jedijunk

    jedijunk Full Member

    So when it's off or idling, it's right between 14 and 15 volts. When I rev the engine at all, it goes up as high as 20.
     
  5. Duct Tape

    Duct Tape Full Member

    you have a problem with your charging system. get it checked out soon before you fry things in your car. its not the amp i would be worried about at this point. go to a mechanic.
     
  6. aznboi3644

    aznboi3644 Full Member

    Yeah if the voltage goes up to 20 than u have a serious problem. Most amps have failsafes from voltage spikes. As Duct Tape said go get that **** checked out.

    Also tell your friend who said to ground the amp to the negative battery terminal that he a a dumbass for even saying that let alone trying it. Sorry but that is just plain funny.
     
  7. jedijunk

    jedijunk Full Member

    Thanks a lot for the info guys. Ever hear of a bad multitester? I'm starting to suspect it...

    We were driving tonight, and once again the amp decided to stay on even when I accelerated. Curious, we went home and immediately tested the voltage without turning off the car. The voltage was steady at 19, and it only went up to 19.5 when I revved the engine.

    Someone theorized that the amp had "warmed up" (we'd been driving for a while) but I dunno.

    Someone told me that voltages work different in older cars?!? Or is this just a bad tester? Or is my car truly ready to blow...

    Teddy
     
  8. Duct Tape

    Duct Tape Full Member

    if you suspect something is wrong with the multimeter, then try it on another car.

    i dont know why you think this though. you are having problems with your amp, and the voltage on your charging system is going crazy.

    you are consulting way too many people that have no idea what they are talking about. take your car to a mechanic. your friends have no clue and they are giving you misinformation.
     
  9. jedijunk

    jedijunk Full Member

    Thanks so much for the help. Talked to a professional as you suggested. So the tester is fine, and my voltage is really just out of control. The voltage regulator in the alternator is shot, and it turns out that the vehicle is still using the original stock alternator - pretty impressive, anyway.

    Plan on replacing the alternator tomorrow, and will report back. Oh, and just to add insult to injury, both my headlights died, due to the voltage I'm sure. The stereo stayed off today.

    Just a question from my friend who is taking this thread personally: what's the difference between grounding something on the negative pole on the battery and the frame of the car, since the battery itself is very obviously grounded to the frame of the car?

    Thanks again!

    Teddy
     
  10. aznboi3644

    aznboi3644 Full Member

    Grounding a amp from the inside of the car to the battery in the engine=too long of a ground.

    You want the shortest length ground wire possible. The longer the length equals more resistance. Ever notice that the ground from the battery to the chassis is pretty short and not 10 feet in length to the back of the car?

    A ground wire from the amp to the battery would cause the amp to not ground properly and possibly overheat and cause some damage. Also the amp would probably not be producing full output due to improper grounding.
     
  11. Duct Tape

    Duct Tape Full Member


    there isnt anything wrong with grounding the amp at the battery, its just totally unnessary. the metal chassis of the car will provide just as good of a ground provided that you cleaned away any paint, and you bolt it in tight.
     
  12. jedijunk

    jedijunk Full Member

    Thanks - that makes a lot of sense.

    So I replaced the alternator today (and thus the voltage regulator within) and that definitely evened the voltage out. Now I'm left with two questions:

    1) Although the voltage has evened out, it evened out at about 14.5V. So I can accelerate or idle or have the car off, and its at 14.5V - not 12.5 as you all recommended. Why is this?

    2) The Kenwood site seriously sucks. I can't find a simple manual for an amp. Any idea where I can get ahold of a manual for an eXcelon KAC-X401M amp either in print or online?

    Thanks!

    Teddy
     
  13. Duct Tape

    Duct Tape Full Member

    when the car is running you will see around 14.5 volts. this is a good thing, it means that your alternator is charging your battery. it will not harm the amp, most amps will actually make more power when the car is running.
     
  14. Hautewheeler

    Hautewheeler Full Member

    yes.. 14.5 volts is normal (lead acid batteries charge this way) and then it should be around 12-13 with the car off.

    those voltage spikes are very dangerous. you're lucky that you got away with just two blown headlights.. that could have been much more expensive for you. Kudo's on getting the problem fixed right away. ignoring that would have definitely lead to more pocketburn. (can't even begin to list how much stuff I've fried from the same kinda problems).

    and you're right.. every site I've found that comes up with archived information for the kenwood amp that you have, turns out to be an expired link. I'd suggest sending an e-mail to tech support requesting that information. (tell them that you lost the original in a fire!:D -well, that was almost the truth..he he) I know that model is discontinued, but they are still selling it on several sites, so it shouldn't be a problem for the Kguru's to fish up some documents for you..
     
  15. aznboi3644

    aznboi3644 Full Member

    Toyota tough