"Sounds electrical"-Has anyone had this problem?

Post by **cowboysvolvofan** » 01 Dec 2010, 12:20

Hi. All of the following has taken place over 6 months. I just have not had the time to work on it all at once. Here we go.

I have a stereo system in my 94 850. 2 12"s, nothing serious. When I switch the car power to ACC, I get lots of bump, no problems. When I start the car, MOST OF THE TIME, no bump. Whenever I do get bump, if I turn it up to a respectable level of volume, the subs don't play. When I turn the volume back down, the subs play.

Ok, so I'm going to give a lot of info. so that we're not providing unnecessary feedback. A brand new altenator was installed about 3 montns ago after I blew it (I think I did. It was original) and has been tested from 2 different shops and it's better than good. A brand new battery was installed today. The car fired up like nobody's business and there aren't any other electrical problems to note.

The reason I'm concerned is b/c I don't want there to be a bigger issue than what it seems to be. Here are the things I know for sure: Amp was tested and good, subs are good, alternator is good, battery is good, overall function of electrical components in car is good.

Here is another tidbit. My stereo system worked fine BEFORE I changed the alternator. I did the change myself. I don't think I did anything wrong, Belts are good and tight. System is charging.

Do you think it could be corroded cables? All help is appreciated.

Post by **BEJinFbk** » 01 Dec 2010, 13:59

Put a meter on the power at the amp. See where the voltage goes during use.
The easy way is to run a couple of wires from the power and ground at the amp
up to the front seats and connect the DMM there. Just watch it while you change
the conditions you've described and see if the voltage is dropping low enough
to shut down the amp. Then go from there. "Step 1 - Check the power supply!"

Post by **cowboysvolvofan** » 04 Dec 2010, 16:58

Hi. Thanks for the info. I found out my amp is "going." I adjusted the gain and I had to turn it almost all the way down before the subs would hit. Maybe something happened when my alternator blew.

juggernaught_666 · Post by **juggernaught_666** » 04 Dec 2010, 17:19

I hope this helps, first check the rated resistance on your speakers then on the amp, If the subs are too old the voice coil may have deteriorated, offering less resistance to the amp, therefore the amp may think "oh no I'm going to supply too much power to the speakers" then shuts itself off to protect itself.

Most subs are 4 ohms and most amps are 2 ohms stable this means you can put 2 subs in a paralleled configuration to yield 2 ohms of total resistance which the amp can then use.

I'm speaking from experience as some of my old, second hand subs were overworked and showed a resistance of <2 ohms therefore when put in parallel the represented less then 1 ohm, not good!

Let me know if you need more help.

Post by **BEJinFbk** » 04 Dec 2010, 19:58

cowboysvolvofan wrote:Hi. Thanks for the info. I found out my amp is "going." I adjusted the gain and I had to turn it almost all the way down before the subs would hit. Maybe something happened when my alternator blew.

That's really not giving you a conclusive answer.
It could many any number of things.
Did you check voltages metioned above while it's "quitting"?
Have you disconnected the speakers to to remove the load
from the amp to see if it still shuts down?
WHo installed the amp and how long has it been OK?

You're asking about cables...
Check the voltages at both ends for an answer.