I am confused about my power problem

Hello,

My Car is a 1998 Sunfire, I have a old Rockford Fosgate 12"dvc hooked up to a MTX 1502 amp.  The amp i think puts out like 300 watts rms.  The problem is lately since its the winter I have been having major problems with the Bass.  What happens is that it Just cuts right out.  THe amp is not hot at all.  And my lights dim a lot more than they did about a month ago.  Like i remember when it was warm outside i could turn it up to about 18 and it would only cut out when it was at idle.  Now it cuts out all the time as soon as i go about 15 on my alpine head unit cd-9807. 

So the question is what is better:  A nice new like 720 cranking amp duralast battery or a 105amp alternator.  I am pretty sure the current alternator is a 65amp its the original.  I really dont want to spend that much, so what is going to make the biggest impact.  It really sucks not being able to turn it up anymore.  And will the 105amp alternator make a big difference?  Also are these hard to install?  Please let me know guys I am planning on fixing this tomorrow.

Mike

Check the battery. Sounds like its dying.  Since your not pulling much power a bigger new battery would suffice.

if the battery checks out ok. Let the car warm up, and the inside. Also check the connections.

would i just take it to sears and let them check it?

Mike

If you have a multimeter, check what the voltage is across the battery with the car off.  Then check it again with the car idling.  Lastly, check it with the stereo playing.  The voltage should be almost 12V with the car off, and at least 13V or 13.5V with the engine idling and the stereo off.  I'm a little hesitant to jump on it being a battery problem, unless you find that  the car-off voltage is significantly below 12V. This would likely indicate one or more shorted cells.

The reason I'm not sure it's just a worn battery is that even if the battery is tired, a 65-amp alternator should be able to supply the relatively-modest demands of your amp.  If the problem is the battery, I'd suspect shorted cells.  This will keep the battery from ever reaching 12V, and will draw power from the alternator constantly.

Scott Gardner

65amp stock?  i have a 98 cavalier and its like 105-110 stock.  i had a local shop rebuild it to 165amp for a pretty small fee.  both cars have the same engine... where did you get 65amp from?

also, what gauge wire (power and ground) are you using and where is it physically (exactly) grounded to on the chasis?  also, have you upgraded the power cables under the hood to the same gauge wire the amp is using?  i think stock, the wire from the alternator to the batter is 10gauge.  if you have a 4 gauge power wire to the system... does that make sense to have a 10 gauge supply line?  upgrade the ground cables (batter to engine block and chasis) too.

you guys it was the battery,  As soon as the new duralast was in it was awesome.  I could turn it way up at idle and it didnt even have a problem.  Also it wouldnt even dim the lights.  I am so happy, thanks for your replies.

Mike