What am I doing wrong?

ottostreet

Bought myself a new 1000 watt subwoofer with built in amp. Have installed bassbins before no problem. Can't get this one right though.

All cables are installed properly in the car. However, the fuse in the power cable running to the bassbin keeps blowing. Ive blown five since last night. The one in the bassbin is fine, but its just in the cable. I was thinking it might not be grounded properly and had a look around my boot for somewhere better. Turns out there isnt many obvious locations. Everything seems covered in plastic or something. Can anyone point me to a good grounding spot in the boot of a BMW 318is 99? At the moment its running up and connected to a bolt beside the hydraulic arm for the boot lid. Not sure if this is actually connected to the chassis.

Bugnut

Is there paint between your connector on the lead and the body.

Sand it off to make a good connection. Sometimes bolts in a car are alloy and dont earth as good as you need when you crank it up.

Does it blow a fuse when your not moving?
If its alright when your not moving and blowing when on the road maybe you have piched the + cable somewhere.

Otherwise things like have you got the right fuse in there?
Sorry if you have thought of that but easy to forget.

Good luck

ottostreet

yeah. fuses are correct from what i can tell. 20amp. the car isnt even on when its blowing them. with the cable disconnected and the fuse in, all i have to do is touch it off the positive terminal on the battery for it to blow. then, i tried connecting it with the fuse out, and putting it in. blew immediately as well. i think it might just be down to insufficient grounding. the bolt its attached to is painted. as is the surface underneath.

Bugnut

Sounds like you have a short mate.

Last test take the fuse out of the Sub Amp.

Now with the + connected put in a fuse?
Does it still blow?

ottostreet

yep. fuse out of the bassbin, put last remaining spare fuse in the cable. bang. can only assume its the grounding really.

colm_mcm

check where you've ran the wire through the bulkhead of the car, the insilation on the wiring may have worn and the wire is being grounded.

ottostreet

doesnt appear to be anything like that anyway. wire appears intact. all i can assume is the paint is preventing it from grounding properly. ill sand it tomorrow and see what happens i suppose.

Bugnut

The ground may need to be sorted anyway as it will help the amp run cooler with a decent power supply.

BUT - If you remove the fuse from the SuBox and the fuse in the +itive wire still blows then you must have a short or break in that cable.
By removing the fuse from the Sub you broke that curcuit so therefore took out the earth from the equation.
But the + lead and the car body are making their own curcuit and blowing the fuse.

Is it rubbing on anything, the seat runner, caught in the bulkhead somewhere as suggested.

Is it decent wire too ahould be at least 8awg for that kinda amp and the earth lead the same.

If it isnt decent wire change it now or you may catch fire.

Graham_B18C

Bugnut wrote: »

The ground may need to be sorted anyway as it will help the amp run cooler with a decent power supply.

BUT - If you remove the fuse from the SuBox and the fuse in the +itive wire still blows then you must have a short or break in that cable.
By removing the fuse from the Sub you broke that curcuit so therefore took out the earth from the equation.
But the + lead and the car body are making their own curcuit and blowing the fuse.

Is it rubbing on anything, the seat runner, caught in the bulkhead somewhere as suggested.

Is it decent wire too ahould be at least 8awg for that kinda amp and the earth lead the same.

If it isnt decent wire change it now or you may catch fire.

That is exactly what I would be thinking, as you said, you're removing the fuse from the sub so it's a problem between the car battery and the sub.

It's more than likely a short or the cable isn't good enough

TheElf

I know Bugnut mentioned it, but it's an important one so I'll mention it again, make sure the ground cable and power cable are the same gauge, and the ground is on a clean part of the car, with no paint etc.

A good place to ground is the bolt for seat belts in the back, if they are bolted straight onto the body, and in most cars I've done installs in there is a ground in the boot, somewhere near the rear lights, this is the ground for the lights in the back, bolt on there.

Let us know how you're getting on!

EDIT: Just had another read and noticed ye took the ground out of the equation, What way do you have your 12V feed wired up? Usually the blue wire.

ottostreet

thanks guys. will give it another shot at the weekend when i get home. all the cables are 10AWG. it must be the power cable really. the blue wire is running from the amp to the cable for it on the back of the head unit. dont think thats the problem really.

TheElf

Ah rite, sounds good, it's just I've seen people trying to wire up and they have the blue wire in the oddest of places.

ottostreet

aha. power cable was after fraying at the point where it crosses between the engine and passenger compartment. That must be it! Anyone have any suggestions as to where you run the cable in a BMW E36 coupe? Because I don't think the place I was running it is correct because its impossibly tight!

JimmyCrackCorn!

ottostreet wrote: »

aha. power cable was after fraying at the point where it crosses between the engine and passenger compartment. That must be it! Anyone have any suggestions as to where you run the cable in a BMW E36 coupe? Because I don't think the place I was running it is correct because its impossibly tight!

Use a grommet or cut ap a piece of fuel hose to make your own to protect the cable.

Bugnut

It had to be .

Glad you found it though, really you should be thanking your lucky stars that it was grounding sufficiently to blow the fuse as otherwise you may not have noticed the sparking and you could have had a fire.

Always have a fire extinguisher in the car if you fit even the most modest of Amp set ups - they are cheap and save your pride and joy.

Sorry about that - a bit lecture like.

Anyway back at the garage - on the bulkhead/firewall (the bit deviding the engine from the cabin) there should be space where the main wiring harness passes through but if not you could drill your own hole.

There are little dimples in the metal to pinpoint where you can drill safely without causing damage - then you need a gromet as mentioned above to line the hole .

Go for some new cable though - if you can afford it - about 20euro should do it, 8awg is thicker( the lower the awg number the thicker the wire) and will be better insulated also.