Advise please

[Chrisj CMA]

OK, after reading about the guy that almost burned up his bike due to wiring.....I got to thinking.  The only real addition I have wired in myself is the voltmeter.  I ran a wire directly from the battery to the meter and then a ground from the meter through a switch so it doesnt just stay on all the time.  But, I didnt think to place a fuse in there anywhere.  Would the fuse need to go on the hot lead, or could it go on the ground wire?    Should I add a fuse at all, if so what amp?  What I dont want to do is restrict the amperage flow and have a faulty reading.......I know many of the "hot leads" I tried to tie into didnt give me the same reading the direct line to the battery does

TIA

[Titan]

Chris, here's a link to some comments in a forum that will help you with that question. The forum has nothing to do with motorcycles but the principle is the same for wiring.

I've always placed the fuse close to the beginning of the hot lead... Except when I didn't use one at all and almost burned my bike up!  

In my case yesterday, when the pair of wires shorted out, they instantly got so hot that the insulation between them melted and the two wires came into contact with each other pretty much from one end to the other. That made a dead short all the way down the wires completely back to the battery so I couldn't stop it since it was under the seat and out of reach.

Somebody else here will know more than I do on this subject but I don't see why an inline fuse would alter the operation of your meter in any way. Basically that fuse is ultimately just more wire for the current to pass through.

In any case, as my incident points out, if your wire shorts out for any reason, you're facing a bad situation.

http://www.expeditionportal.com/forum/showthread.php?t=27090

[Chrisj CMA]

Thanks Titan, glad you didnt have a catastrophe........I guess Im leaning towards the POS (hot) lead but some comments on that forum said either would do the job.  I still wouldnt know what amp......is 30A too high?

[Titan]

Yep. I was lucky. It's a scary thing to be seeing a whole lot of white smoke billowing out from under the seat and not being able to stop it.

The forum does say either negative or positive side will work. That's because it's just a complete circuit from where the hookup starts all the way to where it ends at the ground. So a fuse at any point in that loop would break down and stop the flow of electricity, the same as disconnecting the wires at any point.

As for the size of the fuse, you should use one just stronger than the amount of amps that your device constantly pulls. So, if your meter needs 2 amps then you could fuse it at 5 amps. (that's just an example) What you want to happen is for that fuse to break down if that circuit pulls any more than it should. There's usually a lot of 1 and 2 amp fuses in cars. I haven't looked lately but there probably are as well on the bike.

[Ricky-D]

With that gauge you should need nothing more than it takes to work it, which is probably around a half amp or so, barring the lightbulb.

A two amp fuse ought to be plenty Chris.

***

[Chrisj CMA]

With that gauge you should need nothing more than it takes to work it, which is probably around a half amp or so, barring the lightbulb.

A two amp fuse ought to be plenty Chris.

***

Wow ricky.....see thats why I asked for help.......I would have thought the power coming directly from the battery would immedialty toast a 2A.  I think the smallest fuse on the bike would be a 5A......So if I used a 5A in-line on the ground wire would that be a safety for my set-up, or would it be better to with the hot lead?

[98valk]

amp meter needs a fuse, volt meter does not. using the wrong gauge wire will cause overheating which will cause the insulation to fail/melt and then short out. only use gauge wire size recommended going too large and can cause problems also.

I have autometer gages installed IAW their instructions for a few yrs now, no problems.
follow this and u will be fine.

http://www.autometer.com/download_instruction/1079A.pdf

[Bobbo]

amp meter needs a fuse, volt meter does not. using the wrong gauge wire will cause overheating which will cause the insulation to fail/melt and then short out. only use gauge wire size recommended going too large and can cause problems also.

ANY wire connected directly to the positive battery terminal needs a fuse, preferably as close as possible to the battery.  The fuse rating is determined by either the maximum current of the device, or the maximum current capability of the wire.  A voltmeter is very high impedance, so it will draw very little current, probably microamps.  If it is lighted, it may draw an amp or so depending on the bulb.  A 5 amp fuse should be plenty of protection, and won't have a noticeable voltage drop, so your voltmeter won't be affected.

What problems are caused by too large of a wire gauge?

[Daniel Meyer]

What Bobbo said. Fuse on the hot wire as close to the battery as you can make it. Remember, your bike is a negative ground. Everything metal on it is a negative post. You need to protect your positive wires from shorts to anything metal due to chafing, pinching or whatever.

[Titan]

amp meter needs a fuse, volt meter does not. using the wrong gauge wire will cause overheating which will cause the insulation to fail/melt and then short out. only use gauge wire size recommended going too large and can cause problems also.

ANY wire connected directly to the positive battery terminal needs a fuse, preferably as close as possible to the battery.  The fuse rating is determined by either the maximum current of the device, or the maximum current capability of the wire.  A voltmeter is very high impedance, so it will draw very little current, probably microamps.  If it is lighted, it may draw an amp or so depending on the bulb.  A 5 amp fuse should be plenty of protection, and won't have a noticeable voltage drop, so your voltmeter won't be affected.

What problems are caused by too large of a wire gauge?

Exactly right. It wouldn't matter where that hot power wire (positive lead off the battery) was going or what it was going to serve. Once it's a couple of inches or so away from the battery terminal it can come into contact with other wires or parts of the bike, creating a short circuit. It's a hot wire and if it were to come into contact with ground it will short out with potentially serious consequences, so it needs to be fused.

[Chrisj CMA]

OK thanks guys......I got just the info I needed, I will stop by and get the parts tonight and perform the surgery 

[Titan]

Oh, and all that being said... why did I attach an auxiliary power plug directly to my battery without a fuse? I have inline fuses on hand and I know better! Never once have I done that in my life. So, in my case, it was simple oversight added to basic stupidity. I've even replaced the battery since I made that hookup and didn't think about it then either! You can bet that I've kicked my own butt over this and won't make that mistake again.

Just imagine how that would have worked out if it had lit up while I was on the highway! Or if it had blazed up enough in the garage yesterday that my fire extinguisher (didn't have to use it) couldn't have handled it and taken out the garage, one of my cars, and maybe the house!

This is what happens when stupidity and luck gets together. This time I was lucky!

Hopefully other folks will read and heed. Like HotGlue said earlier... "Fuses are your friend."!

[98valk]

amp meter needs a fuse, volt meter does not. using the wrong gauge wire will cause overheating which will cause the insulation to fail/melt and then short out. only use gauge wire size recommended going too large and can cause problems also.

What problems are caused by too large of a wire gauge?

Basically the wire acts as a resistor and ohm’s law applies (voltage drop = current drawn X resistance).  The designer recommends a certain size wire for various reasons. one is if too large a wire is used to install a gauge then the voltage will be higher and reduce the life of the gauge.
That was an old trick to increase bulb brightness, increase the wire gauge at the expence of shorter bulb life.

[Bobbo]

amp meter needs a fuse, volt meter does not. using the wrong gauge wire will cause overheating which will cause the insulation to fail/melt and then short out. only use gauge wire size recommended going too large and can cause problems also.

What problems are caused by too large of a wire gauge?

Basically the wire acts as a resistor and ohm’s law applies (voltage drop = current drawn X resistance).  The designer recommends a certain size wire for various reasons. one is if too large a wire is used to install a gauge then the voltage will be higher and reduce the life of the gauge.
That was an old trick to increase bulb brightness, increase the wire gauge at the expence of shorter bulb life.

Of course copper wire has resistance, but using the gauge of wire to control current to a device is crazy!!   

To say a larger gauge wire can damage a device is ludicrous.  An example:  Say a device is connected using 3 feet of 18 gauge wire.  That wire has 6 milliohms of resistance.  If the device draws 5 amps, there will be a voltage drop of 30 millivolts, and the wire will dissipate 150 milliwatts of power.  Now we change to a 10 gauge wire.  The new wire has 1 milliohm of resistance, and has a voltage drop of 5 millivolts, and dissipates 25 milliwatts of power.  The device connected would see a rise of 25 millivolts.  I can't think of anything that would be damaged with an extra 25 millivolts...

[Chrisj CMA]

OK   not too bad.  The 5A inline fuse box is a couple inches from the (+) battery post.  Volt meter still reads 13V with the motor off and 14V with it running and now that hot lead running under the tank is not doubling as a fuse for the 5 gal gas bomb sitting on top of it  

What I did was.....I already had a battery tender hookup connected to the battery and I use that to plug in  a power point that runs my compressor in case of a roadside flat.  so when I went to hook up the Volt meter, I didnt want yet another wire going directly to the battery so I cripped on a connector and just plugged it into the "hot" side of the battery tender thinggy.  Instead of fusing the actual wire going to the volt meter, I put the fuse on the positive lead of the battery tender thinggy, so now whatever is plugged into that thing now is protected by that 5A fuse.  Now Im wondering if the compressor would draw more than 5A....I may need to change out that fuse whenever I get ready to use the compressor.......I carry plenty so thats not a real big deal

Thanks again everyone

[98valk]

amp meter needs a fuse, volt meter does not. using the wrong gauge wire will cause overheating which will cause the insulation to fail/melt and then short out. only use gauge wire size recommended going too large and can cause problems also.

What problems are caused by too large of a wire gauge?

Basically the wire acts as a resistor and ohm’s law applies (voltage drop = current drawn X resistance).  The designer recommends a certain size wire for various reasons. one is if too large a wire is used to install a gauge then the voltage will be higher and reduce the life of the gauge.
That was an old trick to increase bulb brightness, increase the wire gauge at the expence of shorter bulb life.

Of course copper wire has resistance, but using the gauge of wire to control current to a device is crazy!!   

To say a larger gauge wire can damage a device is ludicrous.  An example:  Say a device is connected using 3 feet of 18 gauge wire.  That wire has 6 milliohms of resistance.  If the device draws 5 amps, there will be a voltage drop of 30 millivolts, and the wire will dissipate 150 milliwatts of power.  Now we change to a 10 gauge wire.  The new wire has 1 milliohm of resistance, and has a voltage drop of 5 millivolts, and dissipates 25 milliwatts of power.  The device connected would see a rise of 25 millivolts.  I can't think of anything that would be damaged with an extra 25 millivolts...

even though u like to demean me, I will ask u this, Can a 22 gauge wire be used in a circuit that calls for an 18 gauge wire?

[Bobbo]

even though u like to demean me, I will ask u this, Can a 22 gauge wire be used in a circuit that calls for an 18 gauge wire?

I'm not trying to demean you, but when you post things that are misleading, I might respond, mainly so as to not confuse others who may follow bad advise.

If a circuit calls for a specific gauge wire, it is usually the minimum gauge.  A larger wire can be used as long as there isn't a restriction such as termination or a passage.  Since a 22 gauge wire is smaller in diameter than 18, the general answer is no.

[98valk]

even though u like to demean me, I will ask u this, Can a 22 gauge wire be used in a circuit that calls for an 18 gauge wire?

I'm not trying to demean you, but when you post things that are misleading, I might respond, mainly so as to not confuse others who may follow bad advise.

If a circuit calls for a specific gauge wire, it is usually the minimum gauge.  A larger wire can be used as long as there isn't a restriction such as termination or a passage.  Since a 22 gauge wire is smaller in diameter than 18, the general answer is no.

incorrect. if the insulation is upgraded to a better material which can handle the addtional heat from the smaller gauge, there are no issues.
if u didn't know that, then that explains why u didn't understand or have knowledge of my other post.  this is some basic electrical design info.
I'm done with any more reponses from u.

[Bobbo]

even though u like to demean me, I will ask u this, Can a 22 gauge wire be used in a circuit that calls for an 18 gauge wire?

I'm not trying to demean you, but when you post things that are misleading, I might respond, mainly so as to not confuse others who may follow bad advise.

If a circuit calls for a specific gauge wire, it is usually the minimum gauge.  A larger wire can be used as long as there isn't a restriction such as termination or a passage.  Since a 22 gauge wire is smaller in diameter than 18, the general answer is no.

incorrect. if the insulation is upgraded to a better material which can handle the addtional heat from the smaller gauge, there are no issues.
if u didn't know that, then that explains why u didn't understand or have knowledge of my other post.  this is some basic electrical design info.
I'm done with any more reponses from u.

The following chart shows absolute maximum current capabilities of copper wire at 30 C ambient.  You can clearly see that a 22 gauge wire's maximum current with 200 C Teflon insulation is 13 amps.  By comparison, an 18 gauge wire can carry 15 amps with the lowest temperature insulation.




If you self heat a copper wire at a temperature that exceeds the insulation temperature, you would have a HUGE voltage drop, not to mention corrosion and eventual failure.  Not a good design practice in any application.  In this example a 22 gauge wire carrying 13 amps would have over 8 volts drop across that same 3 feet of wire.  At 50 feet, it would drop 136 volts!   

[Earl in Pensacola]

Hey Jeff:  As you may recall I too have a hardwired volt meter (fused) and its wired directly to the battery.  It's been connected that way for at least 9 years with no problems.  Would be happy to have you take a look at it.  By-the-way, I think the charger power lead is already fused (?).  Will check that too, just to make sure.

Sure seems like some "other wires" on this forum are gettin' hot too.   LOL!

[Chrisj CMA]

Hey Jeff:  As you may recall I too have a hardwired volt meter (fused) and its wired directly to the battery.  It's been connected that way for at least 9 years with no problems.  Would be happy to have you take a look at it.  By-the-way, I think the charger power lead is already fused (?).  Will check that too, just to make sure.

Sure seems like some "other wires" on this forum are gettin' hot too.   LOL!

the charger lead I have had no fuse, but it does now   

[98valk]

The following chart shows absolute maximum current capabilities of copper wire at 30 C ambient.  You can clearly see that a 22 gauge wire's maximum current with 200 C Teflon insulation is 13 amps.  By comparison, an 18 gauge wire can carry 15 amps with the lowest temperature insulation.




If you self heat a copper wire at a temperature that exceeds the insulation temperature, you would have a HUGE voltage drop, not to mention corrosion and eventual failure.  Not a good design practice in any application.  In this example a 22 gauge wire carrying 13 amps would have over 8 volts drop across that same 3 feet of wire.  At 50 feet, it would drop 136 volts!   

[/quote]

thanks for the chart. my question should have been one gauge smaller not two, if the insulation is upgraded as can be seen in the chart, to a certain max amp level, one gauge smaller can be used. don't work with electrical design items all of the time, when I do and can't find the info easily I will ask one of the electrical engineers.
from the chart u can also see that a wire does act as a resistor and a larger gauge will allow more current through.
this is why even autometer does not required a resistor installed in the power wire to the gauge.
using correct wire gauge with the correct insulation and proper installation does not require a resistor.
I have not seen in the electrical schematics that the OEM gauges and lights have resistors in the power lines.

[Bobbo]

this is why even autometer does not required a resistor installed in the power wire to the gauge.
using correct wire gauge with the correct insulation and proper installation does not require a resistor.
I have not seen in the electrical schematics that the OEM gauges and lights have resistors in the power lines.

The only reason a resistor would be required in a circuit is when the device doesn't self limit the current, as in an LED.  A voltmeter is very high impedance, so the current needed is very small.  The high impedance self limits the current, so no resistor is needed.  Most devices self limit current, so resistors in power wires would be rare.

[Chrisj CMA]

OK now guys......GUYS......you were very helpful earlier, now you are confusing me....impedance, self limiting current, resistors and stuff........my head hurts.  Im going to change my fuse from 5A to 10A so it wont blow when I use the compressor.  If I do that, are the stars going to collide or some supernova gonna explode and end the world too soon?   LOL c'mon already I didnt mean to start a war of higher physics knoweldge...

[Titan]

OK now guys......GUYS......you were very helpful earlier, now you are confusing me....impedance, self limiting current, resistors and stuff........my head hurts.  Im going to change my fuse from 5A to 10A so it wont blow when I use the compressor.  If I do that, are the stars going to collide or some supernova gonna explode and end the world too soon?   LOL c'mon already I didnt mean to start a war of higher physics knoweldge...

Hahaha! I thought the same thing earlier today Chris. All you did was ask a simple question about a fuse and it gets turned into a huge argument! Bet you didn't see that coming! But it seems nowadays that's pretty much a given on this board. 

[98valk]

yea sorry chrisj.
its that sick love/hate thing going on btwn bobbo and me. 

more than u needed to know, I'm sure 

[Gryphon Rider]

Chrisj CMA:

Here's the scoop:
If your gauge has a backlight, you can connect the backlight wire to any circuit which is on with ignition, which is already fused.
The gauge's positive wire should be hooked to the point where you want to take the voltage reading (e.g. accessory circuit or the battery).  If that circuit is already fused 5A or smaller (like the accessory circuit), you're probably fine without a separate fuse.  If you're connecting to an unfused source (like the battery) you should add a small current fuse.  Autometer recommends a 1A fast-acting fuse for their voltmeters (see link below).  The size of wire you should use depends on its length.  Longer runs require larger diameter wire to minimize voltage drop.  If you use 14 gauge wire from your battery to your voltmeter at the handlebars, there will be virtually no voltage drop (roughly 0.3% or 0.04V).  As far as electrical equipment on a motorcycle is concerned, there is absolutely no hazard to oversizing your wires (smaller gauge number).  As far as the discussion about higher temperature rated insulation is concerned, yes higher temp insulation increases the allowable current, but the voltage drop will be the same with the same current and voltage running through two otherwise identical wires.

My advice to you:
1. Run 16 or 14 gauge wire to your voltmeter for the positive AND ground wires.
2. Fuse the positive wire with a 1A or 2A fuse close to the battery.

http://www.autometer.com/productPDF/0990.pdf

[BlueValk]

I agree with gryphon of most everything else.  But, 14 & 16 gauge wire is real heavy for this application.  Typical house wiring is 14 ga.  18-20 would be a whole lot easier to work with, like running through existing wire holders. 
My .02

[Chrisj CMA]

Its been wired and functioning perfectly for years, it just didnt have a fuse.  I originally wired it with 18ga wire....the fuse attachement is 14ga, that was the smallest I could find in the application I wanted.  Im going with 10A so I can use that connection for either the volt meter or the air compressor when needed......this is not an argument, just a statement of fact

[Ricky-D]

Chris, that 18 gauge wire may not be suitable for the compressor you want to put in the circuit. They usually pull a lot of current.

***

[Bobbo]

Chris, that 18 gauge wire may not be suitable for the compressor you want to put in the circuit. They usually pull a lot of current.

***

True,  18 gauge wire can handle 10 amps, but at 3 feet the voltage drop will be nearly 2 volts.  That will make a noticeable speed difference on the compressor.  14 gauge will have less than a volt of drop for the same three feet.  If you don't mind a slower running compressor, the 18 gauge will work.  If the compressor uses less than 10 amps, the voltage drop and speed difference will be less.

Sorry for all the techno-mumbojumbo, but to do things right you need to have some level of detail.   

[BlueValk]

Bobbo,
Didn't you quote this earlier?

"An example:  Say a device is connected using 3 feet of 18 gauge wire.  That wire has 6 milliohms of resistance.  If the device draws 5 amps, there will be a voltage drop of 30 millivolts".

So, at 10 amps wouldn't there be only a 60 millivolt drop, not a 2 volt drop?  Not trying to start anything.  I thought your posts were real useful.  Now, a bit confusing.

[Bobbo]

Bobbo,
Didn't you quote this earlier?

"An example:  Say a device is connected using 3 feet of 18 gauge wire.  That wire has 6 milliohms of resistance.  If the device draws 5 amps, there will be a voltage drop of 30 millivolts".

So, at 10 amps wouldn't there be only a 60 millivolt drop, not a 2 volt drop?  Not trying to start anything.  I thought your posts were real useful.  Now, a bit confusing.

Good catch!  Sorry, I made the calculation for power rather than voltage drop.  Must've still been thinking of maximum current calculations.   

[BlueValk]

Bobbo,
No problemo.  We appreciate the info.

Chris,
Since you started all this   

I just went out and checked my compressor that I keep in the bike.  It plugs into a cigarette lighter.  It came with a 15 amp fuse.  So, I hooked it up to a power supply that was current limited to 10 amps.  The compressor ran fine, and the power supply loaded down to 13v (maintained 13v).

What's that mean?  Your 18 ga is going to be fine.  Your compressor will run strong enough.  There is a slight chance that you will blow that 10 amp fuse.  You might keep a 15 amp on hand. 

Sorry if it is too much, but I'm sure that I saw that horse move.   

[Chrisj CMA]

Chris, that 18 gauge wire may not be suitable for the compressor you want to put in the circuit. They usually pull a lot of current.

***

Holy cow...........Dont you pay attention........do I need to draw you a picture, maybe just think before you type.  The fuse thinggy is 14 guage, looks like the battery tender thinggy is 16ga.  I wired the volt meter with 18ga.  Now go back and read, the volt meter is plugged into the charging thinggy.  That 18ga wire has to be unplugged to allow me to plug in the powerpoint for the compressor.  So the compressor will not be utilizing any 18ga wire.  Sheesh, next time Ill draw up a diagram and fax it to RickyD Bobbo and CA, wait a week and after the dust settles maybe Ill be able to change a light bulb on the bike without killing myself

[Chrisj CMA]

Bobbo,
No problemo.  We appreciate the info.

Chris,
Since you started all this   

I just went out and checked my compressor that I keep in the bike.  It plugs into a cigarette lighter.  It came with a 15 amp fuse.  So, I hooked it up to a power supply that was current limited to 10 amps.  The compressor ran fine, and the power supply loaded down to 13v (maintained 13v).

What's that mean?  Your 18 ga is going to be fine.  Your compressor will run strong enough.  There is a slight chance that you will blow that 10 amp fuse.  You might keep a 15 amp on hand. 

Sorry if it is too much, but I'm sure that I saw that horse move.   

Thanks BlueValk.......Ill take your advice and change to a 15A instead of 10

[Bobbo]

Sheesh, next time Ill draw up a diagram and fax it to RickyD Bobbo and CA, wait a week and after the dust settles maybe Ill be able to change a light bulb on the bike without killing myself

That's fine, just don't include a question about oil or tires, and we'll get back to you in less than a week!!       

[Chrisj CMA]

Sheesh, next time Ill draw up a diagram and fax it to RickyD Bobbo and CA, wait a week and after the dust settles maybe Ill be able to change a light bulb on the bike without killing myself

That's fine, just don't include a question about oil or tires, and we'll get back to you in less than a week!!       

LMAO