battery install/DECC whoops resulting in subwoofer pulsating

[formerathlete]

I'm totally embarrassed to write this but I need some help/guidance from those of you who are more knowledgeable than me when it comes to 2000 X-22 electrical systems (basically all of you). 

I ended hooking up my old 10" sub and 200w amp last weekend and it worked great with no issues.  Then, I purchased a blue top D34m battery to take on the challenge (Pep Boys online had a great deal--still might, for those interested). 

As I started to install the battery, I started first by connecting the DECC ground wire to new battery threaded accessory post (negative side). What I didn't notice is that the main negative cable had wandered over and was just barely touching the main positive terminal on the battery (nooooooo!!!!).  So, once I pushed the ground wire onto the threaded negative post on the battery, I had a fireworks show.  I immediately tried to pull the ground wire off the post but couldn't get it off fast enough because it was getting caught on the threaded post and I wasn't pulling it calmly enough to get it off the threads quickly. As I was fighting the wire, I saw smoke coming from under the dash on the port side of the steering wheel under the dash (where the DECC ground wire is connected,I never did see the actual source of smoke, though).  I finally got the ground wire off (it was getting hot, too).  Then after it was all over, I finally realized that the main negative cable had been barely touching the main positive on the battery and I was just pissed at myself for not preventing that from being able to happen. Dumb mistake and as my pilot dad always says when small planes crash...it was pilot error.

So, I decided to forge ahead and hook everything up.  ALL accessories worked (still do, thankfully) and it appears that I may have dodged a bullet as it relates to functionality of the boat accessories, I think.  BUT, when I play the radio, the sub works great but there is a new low frequency pulsating bass sound coming from the sub.  Just enough to notice and annoy me. When I unplug the RCA cables from the amp or the head unit, it goes away (can't hear it from boat speakers, anyways).  The sub also 'pop's' when in use and I turn on ANY accessories on the dash.  I hooked up a different amp to the system and still get the same symptoms. So, I don't know what it could be?  Should I replace the main ground wire that connects to the battery and ground post on DECC or could it be the Head Unit that could be compromised or maybe even the DECC (even though accessories are working fine)?  Not sure where to look next.  The ground wire insulation seems ok from battery to DECC.  I am not using a capacitor or anything like that with the sub/amp wiring.  Just 10 gauge power and ground wire from amp to battery and 25 amp fuse on power wire from amp to battery. 

Any help from you guys would be awesome.  You're the only ones I can go to and you're all so helpful.

Thanks,
BJ 

[formerathlete]

Update...tested the ground wire that goes from the black relay box under the dash (DECC??) that has all the orange wires connected to it.  Wire is fine.  I also ran the head unit ground straight to the battery to see if it still has the pulsing, it does.  I've checked all fuses that I can find and all are good.  Ran the boat on the hose and it ran fine but I noticed that the volt gauge seemed a little more erratic than it normally does and I also noticed that the alarm that goes off when the key is in the start position no longer sounds off.  Bizarre.  So, I'm guessing it's probably not the radio, it's something else.  Maybe something to do with the alternator?  Is there a voltage regulator that could be compromised?  I'm stumped. 

[Capt Rick]

The amp should be connected to a dedicated battery with a battery isolator. Read voltage on the output side of alternator and the positive and and negative of the DECC terminals any drop in voltage will need a bigger wire for both from battery.

If the switch's flicker it time to replace it with analogue switch kit I made. 

Capt Rick

[formerathlete]

Thanks Capt.  Took the boat out on the lake today for the first time since I did the timing belt job and had the battery snafu and it ran perfectly (phew).  I kept the subwoofer RCA's disconnected and it everything worked like normal (no gauge irregularities or accessory problems). I tried plugging in the RCA's to the head unit and the sub immediately began pulsing, so I left it disconnected.  I'm guessing it is isolated to the subwoofer/head unit and probably due to the fact that I only have 1 battery running everything.  I think I'll just pull the subwoofer and amp out and put them back on my garage shelf.  Not interested in wiring in an entire new battery system for a mediocre small subwoofer and amp. I'll still do an alternator and DECC voltage test though but I have a feeling they are ok.  How much is your analog device and what exactly will that improve performance-wise? 

Really excited about the timing belt job being such a success, though.  Huge relief.

Thanks,
BJ

[Capt Rick]

DECC   Send PANEL W/O KEY SWITCH + DECC and 2 button with orange wire Rick Cohn 10200 Newington drive Orlando, Fl 32836           575.00 +   35.00 shipping

[formerathlete]

UPDATE...replaced the stereo head unit and it solved the subwoofer pulsating problem.  My little wire accident must have fried something in the stereo that caused it to send a bad signal to the amp/sub.  Problem solved, it seems.