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Fuse under the hood blew, please help

 

Biggamehunter
Unregistered guest
My friend and I hooked up my Verge Mono Subwoofer Amplifier - around 200 RMS, and an MTX 12" 400 watt peak sub. That night I drove home and it was playing fine, if anything a bit quiet, but playing nonetheless. Then this morning, I start up the car to fine tune the amplifier settings and my sub isnt making any noise, I check and see the power light on the amp is off, and then I check under the hood and the fuse is blown. I bought a wiring kit for my amp which is good for a 500watt system. As far as I can tell, the wiring is fine. One thing is that the input and LPF settings were all the way up this morning, meaning they were all the way up last night. Can someone please tell me why this may have happened, and then, what I should do to fix it? I mean, of course I'll need a new fuse, but what kind should I get, and if I get a new one, whats to stop this from happening again? Thanks.
 

Gold Member
Username: Its_bacon12

Hfl, Ny Usa

Post Number: 1045
Registered: Dec-03
you need a bigger fuse under that hood of yours

you may have touched power and ground together or something by accident, that will definately do it
 

Biggamehunter
Unregistered guest
Alright thanks, I was thinking 500 watt fuse would be enough for a 400 watt peak amp and sub. What size fuse do you think I should try?
 

Damien Rob.
Unregistered guest
What size fuse are you using? That fuse blew for a reason; I wouldn't increase the size tell we know what that reason is... If the fuse came with the wiring kit and you are using well under the max ammount of current the fuse actually may be to big to correctly protect your system already. Making the fuse larger will only make the protection you have even less if it didn't blow due to overload... With this in mind a fuse might have blown if one of your positive wires grounded out somewhere or if something got wet (dew/rain/spill/etc..).

1. Where did you mount the fuse holder?
2. What gauge wire are you using?
3. What size fuse are you using?
4. Did the fuse come with the kit?
5. Is it possible something conductive touched the amp terminals or anything else related?
6. Has it rained, have you washed your car?
7. How did you connect the power cable to the battery?
8. Did you check the cable(s) to make sure their are no cuts in the wire casing?
 

Biggamehunter
Unregistered guest
Ok, I went down to my car and checked everything out...
The fuse holder is mounted near the battery, it came installed into the power wire with the kit. Theres about 6 inches, no more, of power cable coming from the battery before the fuse appears.
The wire gauge is 8.
The fuse size was 40amp, for up to a 500 watt amplifier, and it came in the Rockford Fosgate 8-Gauge 500W Complete Car Amp Power/Signal Kit.
It is possible something touched the amp terminals, but very unlikely, the wires don't touch each other, and the only other metal thing that could have touched it is the car's metal chassis, but thats a few inches away from my amp. Near the battery, however, after installing the power wire, the positive terminal was unable to be shielded by that rubber cover (the wire stuck out at a weird angle), so the terminal was open, and might have been touched by something, but I can't imagine what...
No it hasn't rained nor have I washed my car.
The way my power cable was connected was between the two metal parts on the car's positive wire terminal, with the bolt of the car's power wire terminal passing first through one metal part of its terminal, then through the hole on the terminal of the amp power cable, then through the other metal part of the car's power wire terminal, and then held down with a nut.
I checked the cables and there arent any cuts in the casing.
 

Damien Rob.
Unregistered guest
Hmm.... The fuse size and wire gauge is correct. This now draws my attention to wiring and the amp itself. I once had a amp that was defective that just blew fuses left and right. I returned the amp and all was well. Try replacing it with the same fuse and see if the fuse blows when listening to music at low volumes for a while. This is a good test to rule out something touching or incorrect wiring. By any chance do you know how much voltage your car is putting out when it's on?
 

Biggamehunter
Unregistered guest
Alright, I just returned from Circuit City, I have a case of 4 40amp fuses and a case of 4 80amp fuses (just incase). And, no, I have no clue how much voltage my car puts out,
 

Biggamehunter
Unregistered guest
Ok, this morning I tried a 40amp fuse. Basically, I disconnected the negative battery terminal, put the fuse in the holder, reconnected the negative battery terminal, and at that point noticed the fuse had already blown. What do I do now? The fuse just blows as soon as I reconnect the battery. I also have 80amp fuses I can try.
 

Silver Member
Username: Deathshadow

Post Number: 158
Registered: Oct-04
If the fuse just blows instantly with no music or anything on something is wrong with your wiring/something is touching/something is wrong with your amp. There are virtually a million possibilities at this point. You're going to have to start at your power source and inspect every inch of wire (especially where your cable passes through your firewall) back to your amp. Then from their check all the other wires. Refer to your amp and speaker manuals and double check everything. It may be something really stupid; maybe glass has an idea.
 

Silver Member
Username: Deathshadow

Post Number: 159
Registered: Oct-04
Putting an 80amp fuse in will not solve the problem it will just increase your chances of a fire and no protection.
 

Biggamehunter
Unregistered guest
Ok, sorry I'm taking so long to respond, but the problem is now solved. I tried what you said, started at the power source and followed the power cable, checked under the first doorsill, and THERE I saw was the problem. My doorsill has two little metal parts one on each end, and one of those was cutting into the wire and the casing melted somewhat at that point. I got that place covered in electrical tape, and tried the fuse again (the fourth fuse!), and everything worked! Thank you very much for your help, I appreciate it, and I can finally listen to my sub!
 

New member
Username: Carguy

Post Number: 1
Registered: Nov-04
Hey there, if the fuse is blowing instantly, then you have a short. Disconnect the power from the amp and then connect a new fuse (40amp). Get a volt meter and measure the voltage on the power wire. Actuall before you even try another fuse, test the positive wire and see if you have a short with the ground using multi-meter. If you don't have a short, then add a new fuse and test the voltage on the positive wire. If it's 12v or higher, then you're fine. Now connect it back to the amp and see if the fuse blows again. If it does, you have a bad amp. Sometimes when you screw the amp to the car, it might ground the case. Some amps have plastic shielding and most don't. Depending on where you install the amp, the screws might come in contact with the ground.
Hope that helps.

 

Silver Member
Username: Deathshadow

Post Number: 167
Registered: Oct-04
No problem, glad to hear that you are back in business. I would move that wire or do something about those metal parts to prevent any future problems/hazards. Bump!
 

Silver Member
Username: Deathshadow

Post Number: 168
Registered: Oct-04
"If it's 12v or higher, then you're fine."

Low voltage would not blow a fuse, quite the opposite actually. Have you really had a problem with the amp grounding to the body of the car? I always found that theory of the amp grounding to the body by mounting/touching it to be quite a myth.
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