Electircal Woes

[1WheelWonder]

I recently got around to finishing up my fully built ka-t, and decided it was time to start her up. I primed it and all that jazz and it fired right up without hesistation, wow that's amazing then 3 minutes later it completely died, not a bog or drop in rpms just no engine. I tired to start it again but it felt like the battery was dying or the starter was on it's last leg so I ran threw the electrical system starting at the battery, I got 12.5v at the battery, 12.5v at the starter and 12.5v at the alternator I also checked the grounds coming and going from the engine and they were fine, I even switched the starter and battery for known good ones. I tried starting it again to luck but noticed a little smoke coming from the engine bay, I found the source of smoke and it was a single black wire that I followed towards the factory coil wiring, I have a msd ignition and coil and relocated the 3 wire resistor and (single wire) out of sight; however it was this single wire that went up in smoke. This wire know has a few bare spots. Is this wire a ground or ot wire? With this wire not grounded I just get Click, click, click when I try to turn it over, with it connected to the chassis it will turn over but it drags like stated in the first few sentences. Any help will be greatly appreciated.
Modified by 1WheelWonder at 5:46 PM 2/8/2007

[Chezedik]

Well, anytime you have a wire burn up, it indicates a short. Because as resistance decreases amperage increases, and so does heat.

That is a ground that connects to the coil. What did you cut out besides the coil and transistor when you put on the MSD?

[1WheelWonder]

I didn't cut or remove anything besides the factory plug that went to the coil that had the black/red wire and the green/black wire.

[Tulsa_S-13]

Well, anytime you have a wire burn up, it indicates a short. Because as resistance decreases amperage increases, and so does heat.

I thought that that only applied to semi-conductors like carbon etc., that as amperage and heat increase, resistance decreases.

With conductors, as voltage increases so does resistance, amperage, and heat.

I could be wrong, but I just got back from a lab involving this.

[Chezedik]

Well, I can tell you for sure that when you short a wire, it will burn the insulator. Also, as resistance increases, amperage will decrease, and vice versa. So it seems reasonable to assume that with a 12v system, as amperage increases, heat must be increasing. So current must be the culprit.

[Chezedik]

Also, heat is one of three factors that will affect resistance. Higher heat = higher resistance. I don't know about semi-conductors, but I can tell that is the case here.

[Edub1]

I thought that that only applied to semi-conductors like carbon etc., that as amperage and heat increase, resistance decreases.

With conductors, as voltage increases so does resistance, amperage, and heat.

I could be wrong, but I just got back from a lab involving this.

WTF? Ohm's law my friend.

I=E/R or amperage = voltage/resistance

As resistance approaches 0, as in the case of a short, amperage increases infinitly or in this case to a few hundred amps. Try to put a few hundred amps through a small wire and it gets real hot.

Anyway, download the FSM and trace your wires.

[1WheelWonder]

I took a quick glance at the FSM and my patience grew thin, so I went and physically traced the one wire to a funky junction consisting of 3 other wires. Two of the other wires lead to grounds, the third lead deeper into the wire loom. I hacked out the burned wire and replaced it with new and attempted to crank the engine nothing, damn. For ****s and giggles I decided to add another ground to the junction from which the culprit wire came from. With a bump of the key the engine instantly fired up. What the hell?

[Tulsa_S-13]

WTF? Ohm's law my friend.

I=E/R or amperage = voltage/resistance

As resistance approaches 0, as in the case of a short, amperage increases infinitly or in this case to a few hundred amps. Try to put a few hundred amps through a small wire and it gets real hot.

Anyway, download the FSM and trace your wires.

Ok, for starters, I was 100% correct. For semiconductors as heat increases resistance decreases. You might be confused thinking that I don't realize that the material used in the wires is a conductor, so yes, for this situation as heat increases so does resistance.

Yes, I know what Ohm's law is, but the fact is I was referring to a characteristic of certain semiconductors such as carbon.

"At room temperature, the thermal energy of the atoms may allow a small number of the electrons to participate in the conduction process. Unlike metals, where the resistance of semiconductor material decreases with temperature. For semiconductors, as the temperature increases, the thermal energy of the valence electrons increases, allowing more of them to breach the energy gap into the conduction band."

Sorry for the confusion. I just wanted to inform Chezedik that what he stated wasn't entirely true.

[Tulsa_S-13]

Also, heat is one of three factors that will affect resistance. Higher heat = higher resistance. I don't know about semi-conductors, but I can tell that is the case here.

Well, anytime you have a wire burn up, it indicates a short. Because as resistance decreases amperage increases, and so does heat.

I was just correcting your first statement. And no, Im not trying to be an ***, read both of these quotes and figure out what the problem is

[Chezedik]

Whoa, easy there. I was not trying to flame you. But how you want to do this is up to you. I was just saying what it is I know about the nature of electricity. I am not an electronics person, and will probably never make my own circuit boards, so when I speak of electricity it is strictly from an automotive standpoint.

Facts:3 factors that affect resistance in a wire are:

wire gauge or diameterwire lengthtemperature of the wire

As pointed out earlier in the Ohm's law example, when resistance decreases and voltage remains the same (as in a 12v system) amperage will increase, ALWAYS! The only way that this cannot be true would be with the use of a voltage regulator, which is just a method of controlling resistance and current direction.

So, I am guessing that you had something in mind when you pointed out that there was something wrong with what I said, why don't you tell me what it is?

[Tulsa_S-13]

Haha, yea I'm not a fan of E and M at allllll.

But here's where I meant to correct you. In your first post you stated that "as resistance decreases, amperage increases, and so does heat."

In another post shortly after you state "higher heat= higher resistance". But wait, earlier you stated that as resistance decreases, heat increases... that's what confused me. I understand what you meant though.

[Chezedik]

Yeah, I caught that later, and while it is right, I can def see where it is confusing.

[Tulsa_S-13]

Yes, and I'm right about semiconductors and everything else!



Ahhh, just kidding. I don't mean to slap you.

[Chezedik]

No, you are just an arogant SOB.

That's the best kind!

[Edub1]

LOL, this is funny.

Resistance caused by heat is negligible in this case. With simiconductors and other electronic components you are dealing in milliamps not in hundreds of amps.

The resistance in the electrical circuits we are discussing here does not concern the wire - a 16 gaugae wire has essentially 0 ohms. In this care resistance comes from the device to which the wire connects. When the wire comes loose, R drops from say 100 ohm to 0.00001 ohm. When the wire heats up it might be 0.0001 ohms. Your amperage will still go hyperbolic.

[Chezedik]

Yeah, we got past that. And the resistance increase is much more than that. It is, of course, too little too late, since at that point, you have a bare wire making multiple paths to ground, or if nothing else, a bare wire that is now useless.

[1WheelWonder]

Talk about a thread jacking, I kid I kid, what do you all think the issue is seein that adding another ground fixed the problem?

[Chezedik]

I would guess that amperage draw was too high, causing excessive heat in the wire, causing higher resistance, causing higher heat, so on and so on. Basically, it is an indicator that the MSD uses a higher amount of amperage than the stock ignition, which is a well known fact. By adding another ground you have changed the nature of the circuit by making it parallel to ground. This decreases the total resistance to a fraction of the original.

The other possibility would be the first that I mentioned, that something shorted to ground. Now since this is a ground wire we are talking about, right? The wire cannot short to ground. But I don't know.

Maybe the most important thing is that if it was fixed by another ground, then just drive your car and enjoy it.

[Edub1]

So, the burnt up wire was a ground.

Two things may have happened - the ground came into contact with a hot that provided enough amperage to toast it or the MSD requires a much larger ground. It should say in the instructions.

More than likely it is scenerio one as a toasted wire is pretty extreem and your hot to the unit is fine. You better check your product litterature though as you could easily burn up the unit that way.

[1WheelWonder]

I actually have the MSD double grounded in 2 spots figured i'd be safer than sorry.

[Chezedik]

That's good, I know that wire is very small. Did you notice the MSD helping your power?