New Headunit not powering on

Hi all. I have a question that I fear I wont be able to solve without money. I have a 2002 Mazda Miata, with 2 6.5" 2 ways running through an amp. Everything was working as it should. I wanted a different head unit. So, when I went to wire it in, instead of disconnecting the battery and taking the car side harness out, I cut and spliced it right there in the radio bay. Now the headunit won't power on. I tried wring the old one back in, and it wouldn't power on. I tested the new one on another power source and it will power up. I checked the radio fuse, and it wasn't blown. So, what is the next place to look? What would cutting and splicing with the harness hooked up and the battery connected do? Thanks for your time! Jason

get out your DMM and see if you are getting 12v. Check your fuse boxes under the hood and the one inside your vehicle, probably around dash or kicks for any blown fuses.

Sounds like you have a blown fuse and just haven't found the right one.

On the plus side, you didn't damage the new HU.

Blown fuse (there are more than one!) cutting through a bunch of wires is not the cleverest thing to do, not sure if trolling or just that daft....

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Originally Posted by dumdum

Blown fuse (there are more than one!) cutting through a bunch of wires is not the cleverest thing to do, not sure if trolling or just that daft....

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Well Gee, thanks......I was that daft.

Yeah, if you cut the whole bundle at once, the cutter becomes a conductor between the power and ground, therefore causing a direct short. There's bound to be a blown fuse somewhere.

I've had a similar issue where it turned out to be a fuse that looked fine but was indeed blown in a way I couldn't tell just by looking at it.

I didn't cut the whole bundle all at once, since I have my speakers connected to an amp. But I did look at my fuses under the hood, and I think I found a large square fuse blown. I don't know for certain, but all the other large, square fuses show green through the window, and this one is showing the copper wire. The fuse is for " all ignition components", so it sounds likely, right

do you have a DMM with a continuity tester? Put it on both sides of the fuse. If you don't get the beep, it is blown.

No. Honestly, I don't know how to use it...or rather what it means. The DMM puts out a pulse, or detects one?

it's a digital multi meter. Can pick up a simple one from Home Depot or Lowes.

They also sell those little yellow Bussman car fuse testers - you can check fuses quickly and easily without pulling each fuse out. Only cost a few dollars - quickest way to check car fuses....

usually the radio/ignition circuit is one fuse and there's usually another circuit and fuse for maintaining clocks/presets.

the latter's usually something like the domelight and/or cigarette lighter.

that said, check your domelight and/or cigarette lighter, see if they work and check those fuses as well.

I appreciate everyone's time and attention. It turned out to be 2 fuses, one under the hood, and the other under the dash. Thanks for making me look beyond my own pissed-off-ed-ness, and get back to the basics.

Glad you got it sorted out and had minimal collateral damage. Always a good idea to step back and calm down so you can troubleshoot in a logical way.

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Originally Posted by Hillbilly SQ

Glad you got it sorted out and had minimal collateral damage. Always a good idea to step back and calm down so you can troubleshoot in a logical way.

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That's for sure.