Voltage falls for no reason :-( Battery old or Alternator goes south??? :-(

[sobi6111]

i got inside my garage today and opened the trunk and so all interior lights were on obviously,and engine was still running and xenon lights were on and music wa splaying and etc. Well anyway,after 2-3 minutes i noticed like lights became darker and then in a second they got back bright. I was liek WTF. Then in another 2-3 minutes it happened again,so interval 2-3 minutes. It feels liek when that happen every2-3 minutes or so,it almost makes engine to stall,but then he gets rmp higer and then lights go back to normal and etc. Any ideas???? What coudl that be?

[Wagner]

The battery would not cause the car to "dim" when the motor is running. That would be an issue of current or grounding. I'd start with making sure the wires on the battery terminals are in good condition, no corrosion. Then I'd have my alternator inspected. You have an aftermarket stereo so you don't know what drain that is putting on a 7 year old electrical system.

[Major04]

Originally Posted by Wagner

The battery would not cause the car to "dim" when the motor is running. That would be an issue of current or grounding. I'd start with making sure the wires on the battery terminals are in good condition, no corrosion. Then I'd have my alternator inspected. You have an aftermarket stereo so you don't know what drain that is putting on a 7 year old electrical system.

with Wagner on this one. Get those two (2) checked...remember that a battery is only a storage unit. The alternator is the only generator.

Measure the voltage across the terminal, with the motor running without accesories and rev up the motor to fast idle. The voltage should read around or at 14volts. If it reads less than 12V, you may have a failed alternator. Turn on all your accesories (heater, radio, headlights) and anything else that draws some kind of power. It should be reading around 14volts, if it is lower than 13volts then the alternator could be going.

Oh, before I forget make sure the belts are tight...but, as wagner stated check your battery terminals and wire first.

GL

[bgsquad]

What about reading the voltage from the OBC? is it the same as having a volmeter on the connectors?

I am reading 12V while off, and 13.5-13.7 idle from OBC...