Blowing Fuses. AAAAGGGGH!!

[c_hayhurst 10+ year member]

I just spent the entire day daisy chaining another amp to a delaer-installed amp. After spending the entire day off work, I got it installed and promptly blew the power cable's inline fuse. The dealer installed amp is a DEI Audio 4x50 running 4 Polk Audio speakers with an RMS rating of 60 Watts. That amp and those speakers have been running in my car for the last 3 weeks with no problems. The power cable has an inline 100 Amp fuse within 18" of the car battery.

The power cable from the battery to the fuse block and the ground wire is 4 guage. I use a fuse block for both the ground wire and the power cable. From the power cable's fuse block to each amp is 8 guage, installed by the dealer on the first amp, installed by me on the second amp.

Today, I just daisy-chained an amp to run my subwoofer. It was a Rockford Fosgate T5002, that I bridged to run mono, with a power rating of 500 Wattsx1 channel at an impedence of 2 Ohms. I wired my dual voice coil Resonant Engineering SE series, 600 W RMS, sub down to 2 Ohms (negative to negative, positive to positive, one negative to amp from one voice coil, one positive to amp from the other voice coil). I used Radio Shack RCA cables to link the output of the first amp to the input of the second amp. The speaker wires for the sub are bridged per the instructions on the amp, with 16 guage wire.

Settings on the second amp (Rockford Fosgate):

Infrasonic Filter- OFF

Gain- Maxxed out

Frequency Setting- 40 Hz

Frequency Multiplier- 1x

If I remember correctly, the gain was intially set really low, and the sub didn't sound worth a ****. I drove around with it a few minutes with the gain set low. s a Rockford Fosgate T5002, that I bridged to run mono, with a power rating of 500 Wattsx1 channel at an impedence of 2 Ohms. I wired my dual voice coil Resonant Engineering SE series, 600 W RMS, sub down to 2 Ohms (negative to negative, positive to positive, one negative to amp from one voice coil, one positive to amp from the other voice coil). I used Radio Shack RCA cables to link the output of the first amp to the input of the second amp. The speaker wires for the sub are bridged per the instructions on the amp, with 16 guage wire.

Settings on the second amp (Rockford Fosgate):

Infrasonic Filter- OFF

Gain- Maxxed out

Frequency Setting- 40 Hz

Frequency Multiplier- 1x

If I remember correctly, the gain was intially set really low, and the sub didn't sound worth a ****. I drove around with it a few minutes with the gain set low. While in a parking lot, I increased the gain and let the stereo play with the engine running. It still didn't sound very good. In about one or two minutes, the inline fuse by the battery blew. Neither amps' fuses were blown and neither were the car's fuses blown. The stereo maintained power.

I think the high gain setting blew the fuse, but I am not sure. Can anyone give some insight as to what made the fuse blow? Thanks.

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[JimJ 5,000+ posts]

Neither amps' fuses were blown and neither were the car's fuses blown. The stereo maintained power.

you mean the amp was still on after the power wire fuse blew?

just need some clarification...

 

[c_hayhurst 10+ year member]

you mean the amp was still on after the power wire fuse blew?
just need some clarification...

Nope. Both amps had no power going to them. The head unit was on, just nothing going to the amps, therefore, nothing coming out of the speakers. The inline fuse by the car battery was blown. Trying to figure out what made that fuse blow.

 

[JimJ 5,000+ posts]

but the amp's onboard fuses didn't blow?

 

[c_hayhurst 10+ year member]

but the amp's onboard fuses didn't blow?

Correct. Now you see why I am confused. //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

 

[jleecong 10+ year member]

My thoughts....

It's quite possible that as you cranked the gains the current draw was over 100A for a extended period of time. Just for testing you could unplug the fuse at the distro block to your 4x50 and just play the subs and see if you are still having a problem. Just the RF amp shouldn't need that much juice. With both amps running you could be running into problems with to much current threw the wire. Depending on the length of your power wire I run a 125A on mine and have never had problems (14ft including inline).

What are the fuse ratings on the amps?

 

[c_hayhurst 10+ year member]

My thoughts....


What are the fuse ratings on the amps?

For the DEI: 2 fuses at 25 Amps, I think it's one fuse for 2 channels, therefore, 2 fuses.

For the RF: 100 Amp.

 

[jleecong 10+ year member]

You need to upgrade your wire to like 2GA minimum. Fuse the wire at 200A (If using 2GA.).

 

[JimJ 5,000+ posts]

i suggest welding cable...i got my 2awg welding cable pretty cheaply online, or if you know any people that weld...

good stuff.

 

[sumone 10+ year member]

my main power wire's fuse has blown a couple of times, all three original amp fuses (1x40, 2x25) are still there.

 

[somekook 10+ year member]

Correct. Now you see why I am confused. //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

ive also blown power wire fuses and not had to replace fuses in the amp.

 

[JimJ 5,000+ posts]

well, sure...that situation can happen if you develop a short in the power wire.

but if that happened, it would be instantaneous, and the system wouldn't work at all afterwards.

 

[c_hayhurst 10+ year member]

I went to my local car stereo shop today and had a tech check out the wiring of my system. Everything was perfect, except one thing: When I screwed the speaker to the box, one of the screws pierced the speaker wire, causing a short in the system. It was the speaker wire used to wire the voice coils down to 2 Ohms.

D'oh!

At least it's fixed now. It sounds MUCH better! //content.invisioncic.com/y282845/emoticons/veryexcited.gif.c26a15f316d23068607f36ddacd7a7ab.gif

 

[jleecong 10+ year member]

I don't think that would have blown the inline under the hood, but whatever works. Maybe the amp was drawing excessive current because of the short.

 

[JimJ 5,000+ posts]

murphy's law, man...

comes back and bites you in the *** every time.