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Old 11-22-2011, 07:22 PM   #1
Join Date: Oct 2011
Location: Ottawa
Posts: 21
After market Amp blowing fuses

Hi everyone,

so I just finished upgrade all 6 speakers, cross-overs, HU, steering wheel connection adapter and ran all the cables needed for my sub/amp. BUT my poor amp/sub isn't working.

As soon as I turn on the engine, the onboard fuse of the amp blows instantly. So, I took out my trusty multi-meter and got some results that look kind of funny:

- ground wire and battery wire have a 12v on ign and 14v when engine runs
- ground wire and power turn on have the same

Does that seem right? I'm guessing the flux is from the alternator.

I'm not sure what to try next. I did notice that the inline fuse at the battery is a 40a and the onboard amp fuse is a 20a (also tried a 30) which blows instantly.

Not sure what to test next. Any suggestions? ... besides going to an audio store for diag's lol. I'm thinking it might be a dead amp.


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Old 11-22-2011, 08:11 PM   #2
Join Date: Mar 2011
Posts: 241
You have a dead short somewhere. What gauge wire are you running for your power and ground? If all those are good and don't seem to be shorting... Check out the wires behind your head unit. It's pretty tight back there you make have nicked a wire

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Old 11-22-2011, 08:27 PM   #3
Join Date: Oct 2011
Location: Ottawa
Posts: 21
I'm running a precision amp kit that came with 8 guage for pwr/gnd. 14g for power on cable. it's rated for 600w and I'm using it on a small 250w amp

I checked the cables behind the HU (3 times now lol) I'm getting to be a pro at dash removal. All the cables are neatly stored away and soldered with shrink tubing covers. I did the install in house to avoid the cramp space limitation.

I'll check the ground again in the trunk area. If I'm able to get a +12 reading from the ground post and bat post on the amp; is that a safe assumption that the wires are properly installed? Sorry for the ignorance, I'm a s/w type of guy lol.
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Old 11-23-2011, 12:15 AM   #4
Join Date: Mar 2011
Posts: 241
Yeah. I'm guessing it's a bad amp then.... Did you get it new? And you said its a 250 watt amplifier ? How big of a sub and what wattage size is it? Im running a 300 watt mono phoenix gold to a 1000 watt pioneer 12. And it bumps pretty good
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Old 11-23-2011, 01:02 PM   #5
Join Date: Oct 2011
Location: Ottawa
Posts: 21
So I re-did the ground today. Attached it directly to the body (paint removed) and I still get the same voltage as mentioned above. I tried it again and blew the fuse instantly with engine starting.

The amp is a couple of years old (I bought it new) and it's been in my closet for a couple of years. I had it powering a 300w mtx 12 inch. Nothing crazy, just a little extra base is all I need for the music I enjoy.

I'm heading out tonight to buy a used FR punch to test with (for 20$ it's worth the try) I tried to get the setup looked at by 2 local shops but one was booked solid and the other was on vacation ... lovely.
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Old 11-24-2011, 11:29 AM   #6
Join Date: Oct 2011
Location: Ottawa
Posts: 21
Yup, dead amp. Installed a 'very used' old FR amp and everything is working perfectly.

I'm going have some fun and take apart the old amp and see if there's anything I can replace (hopefully maybe just a resistor or blown cap)

Thanks for the help!
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Old 11-24-2011, 11:45 AM   #7
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Its going to be the P/S that is blown

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