Over the weekend, my friends and I installed a new head unit, speakers, and an amp into my car. The head unit is a Sony CDXMP30, the speakers are MB Quarts Reference series 5 1/4" coaxials, and the amp is a Rockford-Fosgate 2600x. Right now, an 8 ga. fused (80amp) power wire provides constant +12v power to both the amp and the headunit. The amp is turned on by the head unit'* remote power on lead and the head unit is turned on by the car'* switched +12v ignition lead. We had to do this because we couldn't find a +12v battery lead in the wires the stock head unit was connected to. After a few problems (stemming mainly from removal and re-installation of the car door panels), we were done.

At least we thought. During the process of hooking up the speakers, something went wrong with the car (this all takes place before we finished). The speakers were, for whatever reason, distorting. My friend who was working on the speakers decided to try reversing the wires for the cross-over. He went to turn the car on, and nothing happened. Just a single click. The battery appeared to be fine, but I went and got my father'* battery charger off the porch, and set it to 12v ignition start (or something to that effect). Still nothing. I immediately got fed up, unhooked the battery and decided that we should go inside to eat dinner. After that, we came back out, I disconnected the amp'* wire from the battery, and re-hooked up the battery. The car starts. I have no idea why, but it does. I re-hook up the amp, and the car still starts. Everything appears to be ok (except that the speakers are distorting a little still), and we finish like I mentioned in the first paragraph. This was on Saturday night.

Last night (Sunday), at around 11 o'clock, I went out to get some gas so I would have a full tank for me going to school tomorrow (today). The car turns on fine, runs fine, and the head unit is finally retaining memory. This part of my post is only important to note, because today (Monday) at around 11 o'clock, I went to turn the car on and was greeted by the single-click of defiance. I really have no idea what could be going on, and would appreciate any and all suggestions. Thanks a bunch.

u might have blowin a fuse somewhere in the fusebox and/or amp. I had that problem over the weekend and it was the fuse in the amp.

Well no fuse in the amp has blown, as it still turns on and powers the head unit. I don't know what other fuse it could be, i've never looked at the ones under the hood if those are the ones you are referring to. But how could something be blown? I had this happen once already, and after a while it started again. This has me completely confused.

Update :

I went out and disconnected the battery and the amp, then reconnected the battery. The car now starts. But what could be causing this problem?

could it be a ignition switch or a burned out fuse link?

The fuse link isn't blown, and I don't know what / where the ignition switch is.

I had that problem immediately after I put in my stereo. Turns out I didn't reconnect the battery completely.

Well like I said, this has happened once before. And the battery has indeed been connected properly. My car is a hotbed of mystery.

I don't know if splicing into the other 12v lead could cause a problem, maybe. There is a switched 12v lead in the radio harness, though. My brother and I both found it (we both have 92s, his is an SE, mine is an SSE).

I don't know what you mean. There was no 12v constant in the radio harness, there was a 12v switched though.