toggle switch questions..

[ucdcrush]

Im not a very experienced wire-er, but I'm adding some gauges to my car (tach, a combo oil/temp/voltage, a small aftermarket fuel gauge, and a trans temp gauge) and I would like to be able to look at the gauges without using the key, mainly so I can check my gas level by turning the gauges on. So I want to use a toggle switch.

Would it be OK to power all these gauges off the same wire? How would I go about this? Run a 14 gauge wire from the battery + to inside, to the switch, then attach the 4 gauge positive wires to the switch? Should I put some kind of fuse on the wire to the battery, and what amp fuse would I use?

Thanks..

[GTS225]

Im not a very experienced wire-er, but I'm adding some gauges to my car (tach, a combo oil/temp/voltage, a small aftermarket fuel gauge, and a trans temp gauge) and I would like to be able to look at the gauges without using the key, mainly so I can check my gas level by turning the gauges on. So I want to use a toggle switch.

We first have to know what kind of inputs those guages have.  Tach and voltage is easy.  Oil pressure, water temp, and trans temp....electric or mechanical sender/sensor?
The tach, oil pressure, trans temp, and water temp isn't going to show you anything unless the engine is running.  The temp guages will show you current conditions, but not necessarily accurate readings without the engine or trans actually being used.

Would it be OK to power all these gauges off the same wire?

Possibly.....the guage + wires may only be for lighting....you would have to read the instructions and determine what terminal gets hooked to where.

How would I go about this? Run a 14 gauge wire from the battery + to inside, to the switch, then attach the 4 gauge positive wires to the switch?

That would be about right, but you must put a grommet in the hole in the firewall for this before you run the wire.  You risk burning the car down if you don't.

Should I put some kind of fuse on the wire to the battery, and what amp fuse would I use?

Of course......Always fuse it as soon as possible coming off the primary power source.  If that wire gets cut, chaffed, or otherwise damaged anywhere between the fuse and the battery, you again risk burning down the car.  The amp rating would have to be determined after you have everything wired. Pull an ohms check with your meter between the feed (at the fuse), and ground, with that toggle switch turned on. Voltage/ohms=amps, or 13.8VDC divided by ohms will tell you what amp fuse to begin with. DO NOT go higher than two more amps without determining the cause of the unexpectedly high current draw.


I suggest you hook up just the fuel and volt guage this way.

Roger

[ucdcrush]

Thanks Roger, that is very enlightening info and helps a lot.

The oil press/temp/volts are a single digital gauge, and all the gauges are electrical sending units.

I'm getting the basic wiring in place and once those are in I will do the experiment you outlined to determine fuse size..

[GTS225]

Just to clarify something.  When you do your ohms check, do NOT touch your leads to both the negative and positive sides of the battery.  Many low-dollar meters have no protection, and will burn out faster then you can say $H!T.   Get you wires run to the fuse holder/block, leave the fuse out, hook the negative lead of the meter to ground, and the positive meter lead to the guage side of the fuse holder.  In this way, you won't expose your meter to primary power, you're only measuring how much resistance the primary power will "see" in that circuit.

Not trying to suggest you don't know what you're doing.  I have no way of knowing how familiar you are with electrical meters, or the consequences of hooking something up incorrectly.  (Don't want you blowing up a meter you bought the day before.)

Roger

[ucdcrush]

Thanks again Roger. I am NOT experienced with this stuff at all and don't know what I'm doing , so your explanations are VERY helpful.

I dont know anything about how meters work (I do have a couple multimeters though but only used them to check voltage on batteries so far); in your explanation of what to do to check resistance, where does the power come from if one lead is grounded and the other is not connected to the positive side (just connected to a wire dangling off of the fuse holder)... ? Does the meter send power down the line to see what makes it to the other side and how much resistance there was? I need an electricity for idiots book...

[GTS225]

Yep.....The meter has in internal 9-volt battery that it uses.  It'll use that to see how much resistance there is to current flow through your toggle switch and guages, and back to ground.

Roger

[ucdcrush]

 

Can't believe I got that one right 

[GTS225]

Can't believe I got that one right 

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You're welcome.

See?....They actually tried to teach you all that stuff clear back in junior high and high school, but (like me) you didn't pay attention.  'Course, they called it basic science and/or physics, and it was taught in a really dry fashion.

Roger

[ucdcrush]

Another question comes to mind.. what effect does the wire attaching the fuse holder have on the circuit? For example if I run a 14 gauge wire, and use a fuse holder that has 12 gauge leads on it (about 6" long), would it work properly, or should all the wire, including that of the fuse holder, be 14 gauge?

[GTS225]

Wire guages are inverse....the bigger the number, the smaller the wire.  A 12 guage wire has, (If I recall correctly), a rating of 25 amps under ideal conditions, and a 14 guage has a rating of 20 amps, under ideal conditions. (Those conditions will not exist under your hood.)
So.....The primary feed for the fuse, being 12 guage, will have no effect on the rest of the circuit.

Roger

[ucdcrush]

Thank you again, sir.

[GTS225]

Hey,  UCD.......How'd you come out on this? 

Roger

[ucdcrush]

Hey,  UCD.......How'd you come out on this? 

Roger

Hi Roger - haven't quite gotten there yet. I just put the wiring harness and front wires in last week, now it has headlights and tail lights, but the signals and brake lights aren't working yet. Trying to get those working first, I think I just need to finish connecting some wires. If I can't make it work I'll be back here asking about it

Dave

[GTS225]

Hi Roger - haven't quite gotten there yet. I just put the wiring harness and front wires in last week, now it has headlights and tail lights, but the signals and brake lights aren't working yet. Trying to get those working first, I think I just need to finish connecting some wires. If I can't make it work I'll be back here asking about it

Dave

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A-HA....You mean to tell me/us that your 30 or 40-year old wiring is giving you problems?  How blasphemous!    Mopars are GOOD cars.
Sorry.....tongue-in-cheek there.
It's a bit of a bear getting some of that stuff back into operating status, isn't it?  If nothing else, you'll learn about wiring through the school of hard knocks.

Roger

[MVRCorp]

I would have run 16 gauge......is 14 really necessary?

[ucdcrush]

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A-HA....You mean to tell me/us that your 30 or 40-year old wiring is giving you problems?  How blasphemous!    Mopars are GOOD cars.
Sorry.....tongue-in-cheek there.
It's a bit of a bear getting some of that stuff back into operating status, isn't it?  If nothing else, you'll learn about wiring through the school of hard knocks.

Roger

sadly i think it's all my fault 

I am using the wiring out of a '66 VIP and the brakelights and signals were working. I am not using a heater, radio, clock, lights and such so right now there is lots of unused wire just hanging there. I have the wiring diagrams for my dart and for the VIP, and am trudging my way through it slowly. I think the signals not working is because I did not plug any wires into the back of the turn signal indicators. the brakes lights, i am not sure yet. anyhow i hope to have the basics working this weekend then can go foward with the wiring of gauges.

now that it's been raised, would 16 gauge work OK for the gauges? would rather not go overkill if it's not needed.

[ucdcrush]

Decided to run the 3 way gauge and the fuel level gauge off a switch connected to the battery with a fused line. Seems to be working fine, thanks for your help.

[CudaDon65]

I like the gauges, could you please give more info about your gauges. Thanks Don.

[ucdcrush]

I like the gauges, could you please give more info about your gauges. Thanks Don.

Don- the gas gauge is a Nordskog from summit. i must have been too cheap to buy the one with the blue lights.. The 3 way gauge is one I got when it was on clearance at summit, forget the price but maybe 80 dollars. It's a summit brand and it's made to fit into a radio space (DIN). I think this particular model is discontinued, and I don't see anything like it for sale anymore on summit's site. It looked like a pain in the arse to try to mount it in my radio hole so for now I just attached it to the bottom of the dash.

[CudaDon65]

Dave, thanks for the info. They look real nice. I want to do something like that to my cuda. Not alot of gauges in my 65.

[flyboy01]

OK, there are some simple rules when you do automotive wiring.

1. Always fuse each every wire, its ok to fuse a single feed wire close to to power tap.

2. Make the fuse is appropriate to the wire gauge size. Don't use a 30amp fuse with a 22ga wire.

Wire Gauge     Maximum Fuse Size
00 awg           400 amps
0 awg             325 amps
1 awg             250 amps
2 awg             200 amps
4 awg             125 amps
6 awg               80 amps
8 awg               50 amps
10 awg             30 amps
12 awg             20 amps
14 awg             15 amps
16 awg            7.5 amps

These are the recommended maximum fuse ratings for the corresponding wire size. Using a smaller fuse than what's recommended here will be perfectly safe. 

If you do screw up, Don't ever try to pull a burning wire with your hand, use pliers or cutters.

[MVRCorp]

Nice looking gauges  but what's that rat's nest on the floor.    

[ucdcrush]

Nice looking gauges  but what's that rat's nest on the floor.