weird power problems

Hi, this is my first post on here. I recently installed a Kenwood KAC-929 wired with a Rockford Fosgate 1 Farad Capacitor with power running directly from the battery in my '98 Tahoe with rear air conditioning (I believe it has a larger alternator cause of it). Everything was running great for about 2 days until I made a 3 hour trip. Half way through the trip, subs would go out during heavy bass. I lowered the volume and it would begin to get power again, and soon would cut off once again. The next day I did some testing with my multimeter. With the key out of the ignition, the line before the fuse is getting 12 volts, with the key turned to accessory or with the car started, I will only get 5-6 volts. My friend thought that it possibly had to do with a short in the system, so I checked the line from the battery and didnt find any problems (It's 1 gauge wire btw). So I removed the fuses from the block and checked the voltage again, and it was still reading 6 volts. The only two things that I could think of was that the battery is going bad, or the alternator is going bad. I thought of ruling out the battery considering it was giving me 12 volts when the key was removed though. Any suggestions?

when your car off your should have your battery reading 12 volts when testing the volts try this get your multimeter test youe positive and neg termiels  derectly at the posts like your normally would if you get 12 volts volts good that is were your should be then start your car at your battery post check it again the volts should be 12 to 14.4 volts with your car running this means your alternators working fine if volts drop the 6 volts like you said replace your alternator also check your main power wire from your battery to your amp if it is also not grounding out this could also cause a problemraul villarreal

I did take the capacitor out of the equation by removing the fuses to the block, and measuring the voltage at the battery side of the fuse block. I also did some more testing with the multimeter. With the key removed from the ignition the battery was around 12V, as well as at the distribution block it measured 12V too. Then, I put the key in and turned it to accessory. The battery measured around 12V as well, but at the distribution block, it measured around 9V this time. Both of these times, I had the amplifiers and capacitors unhooked by removing the fuses. My friend also said that if the line from the battery was accidentally sliced and was grounded, that I would know for sure.

have you tried testing the voltagfe output from the back of the alternator? also you could go to an autopart store like kragen and they could do a load test on the battery and test the alt.

I've ruled out the battery and alternator since the deck (which is connected using a wiring harness) says its running at 13.6V (the deck is a Pioneer AVIC-N1). I did a bit more testing. I connected my - lead to the ground for the amps, and the + lead on the battery terminal and got 14V. I turned the accessory on, and it dropped again to 9V. I'm no longer getting the 6V drop, but just getting around 9-10V which is enough to power the amp when the volume is turned down. Anyhow, I tried disconnecting the amp completely and just testing the line and ground, and it went to 14V. As for the fuses, I've already checked them and they are working fine. The problem with the power is before it runs through the fuses. Right now, I'll have to agree it is either a bad ground or a faulty amp, but I'm tending to lean more towards a bad ground since i tripped my friend's amp and it was going through the same problem. I also testing other areas around the amps for good grounds, but I'm still getting around 9-10V. Should I run another line straight from the battery for ground? Can I perhaps use the ground from the rear air conditioning unit in the Tahoe?

Ok, by the sounds of it you have a meter. The ground is the most important wire there is in any car audio system. In any GM vehicle whenever I must install a Rockford amp, I will always ground direct to the battery. It is a little thought of phenomenon called resistance on the ground return. It is not about the size of the metal in the chassis, but the resistance running thorugh the chassis and crappy weld joints and glued together unibody panels made out of recycled coke cans. If you have a meter disconnect the ground wire from the amp. Take one lead of the meter and connect it to the neg terminal on the battery. Take the other lead and connect it to the bare part of the ground wire. With the meter set to DCR it will give you a resistance in ohms, a reading of above .5 ohm is going to affect any amplifier. If the leads of the meter are too short, use a length of speaker wire to extend the probes.Top Secret, I can tell you but then my wife will kill me.

okay, the resistance seemed to be a little high. Would it be safe to use the ground wire for something else in the system? I have a plug under the passenger seat for the optional heat seated option. Coul dI tap into that ground?

No, do not share a ground circuit with something else. Bite the bullet and run some 4 guage direct to the battery. Was your reading up around 23 ohms by chance?Top Secret, I can tell you but then my wife will kill me.