Intermittent loss of electrical power

[khoney]

Hey guys,

My son had an aftermarket stereo installed in his Mazda3 (not by a professional) about 2 months ago. He has been telling me lately that occasionally when he makes a hard right, he loses all electrical power momentarily, power steering loss, etc. He also says that his car cranks a lot before starting the first time in the morning, but if he drives somewhere and stops and restarts it's better.

I'm thinking two things: Some low level constant drain on the battery, and an electrical short of the battery to ground caused by a frayed wire or one with insulation cut. He told me they hooked the power for the amp directly to the battery and brought the cable through the firewall. I'm wondering if the guy bothered to put a grommet in. My most likely hypothesis is that the firewall might have cut through the insulation, and the hard rights are causing contact of bare wire with the firewall.

I've never done a stereo install before, and I'm trying to diagnose this from 1300 miles away (he's stationed at 29 Palms, CA). Any opinions about the likely causes of this would be welcomed.

FWIW, I think he told me the amp was mounted in the hatch behind the driver's side rear seat.

 

[Kain]

Could also be a bad ground for the amp. Without knowing his exact setup, it's kind of hard to troubleshoot. I'm assuming at the very least he has an aftermarket headunit and amp. The first thing to do is to check all the wiring and connections for each component one at a time. First, I would disconnect the amp power wire from the battery and see if the symptoms persist. If they do, then you know where to start.

 

[Sport6]

My first and dumb installation of a sub in my first car went bad as well. I left too much slack in the power line that it actually ended up resting on the exhaust manifold and it melted through the insulation and would randomly ground out on it. It did do the intermittent power loss and then finally the inline fuse blew at the battery.

My guess is that you are right about the power cable is grounding on something, either in the hole that was cut or something else in there.

But like Kain said, disconnect the power for the amp (at the battery) and see if everything clears up.

 

[khoney]

Thanks for the advice, guys. I'll pass it along (although he's 18, so I doubt he'll listen).

 

[Nigelo]

Hi! Check to see if everything has been bolted onto the battery tightly, and get a good ground! When my HIDs were on, my electrics would cut out everytime I put my indicators on or pulled off from stationary. Only thing I had done before this problem was to wire up my amp, so when I tightened up my connections and used a proper ground point, well, my problem never came back!

 

[Kain]

Thanks for the advice, guys. I'll pass it along (although he's 18, so I doubt he'll listen).

He needs to track this down right away, not at his leisure or discretion. There have been many a fire caused by bad wiring in cars.