dctennis10

so i was trying to put a GSW-45 switch in for my cathodes, cuz the switch fits in the empty slots perfectly and it looks better than the little crappy switch that came with the cathodes. i cut the wires from the original switch, attach the main power one to the new switch, and add wire to the second one because it wasnt long enough (i know this is probably my problem, but the extra wire i added was of a lesser gauge than the other wire). i turn on the cathodes, and they work, but then i flip the switch over cuz i wanted it to go the other way, i turn it on and it pops my 3 amp fuse. i replaced it with a 5 amp, and *pop* i lost another. do you think that the extra larger wire is causing this?

NoShiO

umm... i go from 20 gauge to 16 gauge...
but thenagain i tapped into the radio fuse... ( hopefully one day to tap into something else)... i just pinched it to that 7.5 fuse.. and i put an inline (someone told me to ) w/ a 3 amp inside of that
...dono why.. but just did it..
my first DIY w/ electircal.. yay!!


have anice day

TheScionicMan

I'd say something is grounding out. remove the switch and check your connections. Tape them off.

The 3 amp fuse was doing it's job, it can be dangerous to just pop a larger fuse in, you could allow the problem to travel farther than it should. Always check to see how much you are drawing first...

ScionDad

NEVER overfuse. If a fuse blew....it blew for a reason. If the fuse amperage is increased....it may well be the wire that becomes the fuse next time. Then you have fire.

The switch is only breaking the positive connection to the cathodes. +12v into switch from fused battery and +12v out of switch to cathodes. Switch on...complete wire. Switch off ...wire open.

The neg will have nothing to do with the switch.

Also, never control any equipment by switching the neg line (providing and not providing a ground) to turn something on and off.

Lonely_Raven

^^^^^Smart Dude. I'd listen to him.

dctennis10

Indeed, i figured out why. it turns out i didnt strip enough of the wire before i coupled it with the new one. i did it again today and it worked with no problems. thanks for the help guys!

engifineer

On a properly wired simple load circuit there is nothing wrong with swithching the ground, which is what a lot of systems on a vehicle actually do.

Sounds like it was a connection issue. The wire size will not matter as to whether or not the fuse is blown. But I do advise to NEVER use tape to insulate a connection, as this was mentioned. Tape eventually loses its sticky and losens up. Use the proper size of heat shrink to ensure it stays protected.

ScionDad

Yea, I've seen switched ground for signal controls mainly, but not very often for loads dealing with a spst switch. It's alot easier for a shorted wire to find a ground accidently than it is to find a positive accidently, bypassing the ground switch, and that's never good. Now what ever is under power can't be shut off. Depending on what that is (NOS System activated, cathodes, whatever), that may not be a good thing.

So, as a basic rule, if I explain in simple terms and not go into Kirchoff's law....just switch the +pos. If the switch get bypassed by a short to ground, a fuse (which better be there) will blow and their aftermarket product will not work.

Fix the short.

engifineer

You dont have to explain in simple terms. Kirchoffs Current Law states that the amount of current coming into a node equals that going out. Iin = Iout.

Kirchoffs voltage law states the that the algebraic sum of all voltages drops in a closed path circuit must sum to the algebraic sum of the applied voltages.

Both of those actually state that the switch location has no bearing on circuit performance In and of itself.

But if you look at fire and spark safety, then we get the following:

For a switch on the ground side: If the power breaks from the positive side of the switch, and touched a ground on a switched ground, it would have the same effect as the switch being powered on, since the load (the lights in this case) are still in the circuit limiting current flow. The load will just be on all the time. Now, if the ground broke off of the switch, nothing would happen except that the lights would not work. Now... lets look at a switch mounted in the positive lead as you mentioned:

If the positve breaks and shorts to ground, there is no load between the short and ground except the resistance of the wire, so POP goes the fuse or the wire melts if there is no fuse. If the ground side breaks and shorts, then nothing happens smokes or pops, the lights just do not work. So if you are technical about it, the ground side is actually the safer place for the switch.

Now yes, if we are talking about equipment such as NOS I do agree. But in the case of leds or low current tubes it is not much of a concern. ( Not really arguing with you, just letting you know I'm not talkn out my a$$, and that I understand Kirchoffs Laws very well ) On an LED or very low current load, it is not such a big deal. But the point you make about devices such as NOS is very true as there is more saftey risk with the NOS staying on than of the sparks generated from a short under the dash obviously. A fused circuit will prevent wire meltdown, but the instantaneous spark that can be created before some type of fuses blow can also be an issue when inside the vehicle. Look at the dash harnesses that have caught fire due to shorts in the past.

But... I am really not disrepecting, or even arguing with you. Just looking at it from different perspectives... mainly cause its fun to actually discuss with someone(me being an engineering geek and all)

ScionDad

Or in other words, the algebraic sum of the voltages around any closed path is zero just as the algebraic sum of the currents entering and leaving any point in a circuit must equal zero. Besides, I wouldn't attempt to explain method of branch or mesh currents to someone asking to hook up DC lights was my point.

I fully understand the switch location has no bearing on the circuit operation in general. It's just not safer switching ground. Might want to brush up on your NEC.

The theory of the switch is to control. It is much easier for a damaged wire to find a ground source. Now the switch no longer works and what you need control of is out of control. This is bad practice and really frowned upon in general. You can however tick alot of installers off this way

Now we are talking damaged hot wire that is switched and it gets shorted to ground. First, whatever it was controlling is now shut off because a fuse blew due to the short. Either way, the "positive switched"" line worked...the circuit is switched off.

This is the first step in common sense safety, which is, when all things are equal.....Never wire something up that even has the potential of running without your switch. The only way to do that is switch positive.

You will also notice most products with a switch tell you to switch positive and add a fuse. The reason why? NEC. A producer must follow this as well.

Oh, I wasn't taking it bad. Shoot, I received my EE back in 85...when tubes were still hot and TTL was all the rage

engifineer

Hey the sciondad..... there aint nuthin wrong with tubes!!! I am in the process of designing and building a tube amp for my electric guitar.. there is nothing like that sound!!! Luckilly one of my professors back in engineering school did a lot of desigining with old tubes he had and spent some extra time going over tube design. I think he can supply some of the not so easy to find tubes for me :-)

But on a side note... I do also know the NEC, and really wasnt arguing with you. Just looking at it from a different point of view and starting coversation with a fellow electronics guy

ScionDad

Oh, no problem. Didn't take it bad at all. Your very bright and have been helping people on here for quite some time I see. Very nice (and keeps your skills sharp and up to date).

I'm with you, tube amp is still the best in the world. The sound is old school and sweet

engifineer

Have you heard the Sovteks? They are these ugly boxy little tube amps , but have a really sweet sound.