Ford Mustang Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
159 Posts
Discussion Starter #1
Just a quick, probably dumb, ques for the more electrically-inclined AFMers out there. I have this Stinger + battery terminal with a couple of unused 8 ga holes (see pic link). I also have an 18 ga wire I need to run to the + side of batt, for a gauge.



Q: Is it ok to connect (still not certain as to exactly how) two wires of such dissimilar gauges? What little I've found on the subject surfing around relates to residential electricity, and the AC world; not the DC world of autos. I'm guessing this is fine, but could anyone confirm? Or advise if not ok to do?

Thanks!
 

·
Registered
Joined
·
831 Posts
The general rule of thumb is no. That said, hooking an 18g wire to an 8g in order to run a gauge is no biggie. You can hook smaller wires to a larger wire when the larger wire is feeding the smaller wire. An extreme example of bad wiring is hooking your starter to the cigar lighter. The starter needs hundreds of amps while the cigar lighter is fused with a 20 amp fuse.
 

·
Registered
Joined
·
159 Posts
Discussion Starter #3
Thanks. There's no clean way to run such a small ga wire into this Stinger term top that has 8 ga and 1/0 openings, so that's why I was thinking of joining a short length of 8 ga to the 18 from the Stinger.

The connection will be tucked away in some convoluted tubing. Think I'll peel back some of the outer 8 ga strands, wrap the 18 around the 8 ga "core" several times, then lay those outer 8 ga strands back down. Solder it (may have to use the butane torch a little), and shrink tube it up good. There won't be any stress on the connection...

Just trying to secure some + batt "juice" for the new Tach.

Thanks again.
 

·
Registered
Joined
·
1,239 Posts
While I do not know the tach you are using, it is not normal to run a + lead to the battery. Usually a switched source.
 

Attachments

·
Registered
Joined
·
324 Posts
While I do not know the tach you are using, it is not normal to run a + lead to the battery. Usually a switched source.
I totally agree with Explorer, tachs are switched 12 volts usually. Unless maybe its a tach with memory for bringing up last high rpms and all that crap. But if you are correct about it needing constant voltage even in key off state, why run wire all the way to Battery there should be a couple places inside you could jump off of at fuse panel, so you dont have to run wire all the way out to battery. Like Bradley said in his post it is ok to jump off a larger gauge wire. And its just a tach you are not carrying any significant load through a tach, hence the 18 gauge wire. Find a main battery power wire inside and piggyback solder it inside the car. Or I dont know about your model stang but there may be an empty spot in the fuse panel you could make another circuit off of. There are lots of options. If you still want to go out straight to battery and you are using that stinger connector just put it in with the main Battery wire. You can make wiring this tach really difficult or you can make it simple like it should be. If I had the wire ran outside already then I would stuff it in with main battery wire there is no harm in that at all. if you are using the 8 gauge side running another wire inside for some purpose stuff it in with it at the connector. If im correct about that stinger you just put the wire inside the hole and crank down the set screw to hold the wire correct? Good luck keep it simple:)
 

·
Registered
Joined
·
831 Posts
Explorer and matthew67stang are steering you in the right direction. I answered your question but I should have offered some more advice. Specifically the advice THEY gave. :)
 

·
Registered
Joined
·
159 Posts
Discussion Starter #7
While I do not know the tach you are using, it is not normal to run a + lead to the battery. Usually a switched source.
Yes, my bad!....busy last couple of days - thankyou for all the posts.

Looking over the Tach instrx again, the "+" I need to head off to is indeed a 12V Keyed Ignition source. And not the + of the Batt, as I had wrongly thought. You are all correct. That I made a mistake (well, almost! lol) in this category is more expected than a surprise!

Indeed, I need to run three other wires, and the + from my elec choke to this 12 V + keyed Ign source. Does anyone know a good place to tap into this?

I see, while being upside down, that there is an unused spot in my fuse box (old style, glass types). Or it could just be that the PO left out an important fuse there. (I only drove this car for a couple hours in the daylight before tearing into it. So its nuances are unknown to me...) Would any circuit in the fuse box be a source of 12V keyed Ignition power? As opposed to always hot, or 12V during start, or Accessory? I'm really at a loss to know what would be good to use for this 12V keyed power location that so many wires need to head off to. Everything else is hooked up. This is the last item I'm up against.

Any suggestions? I'm guessing this is an easy answer, in fact there are probably several. But I know not what they may be.

Thanks all! So appreciated by the electrically-challenged.:worship
 

·
Registered
Joined
·
1,377 Posts
do you have a test light? most of these questions you will be able to figure out if you do. the 12 v keyed on wire is probably just for the light. an easy source for this is your heater wire. or you can attach it to the acc post on your ignition switch. best thing is test with the light and verify the power goes off when the switch goes off.

on another note I just bought one of these powerprobe III testers for my car. it is pricey but man it makes troubleshooting electrical problems so much easier. I have a multimeter but have never really taken the time to understand it. this powerprobe is very intuitive.


Amazon.com: Power Probe III Ultimate 12 to 24 Volt Automotive Electrical Circuit Tester Kit: Automotive
 

·
Registered
Joined
·
1,239 Posts
Fuse panel you'll have to find out whats what from possibily the diagrams listed at top of page in "stickies" mccance: Look at the diagram I posted, white is used for powering tha backlight. I haven't used a fancy tach with all the bells and whistles, but the colors have been standard on every aftermarket tach I've installed. I have the Power Probe, and it is a handy tool, good for powering up stuff, checking relays etc. There are just so many things you can test with a multimeter troubleshooting, you need to take the time to learn it well. It will get you thru the hard to pin down problems that give people so much trouble. Of course, just the plain old test light is still very useful.
 

·
Registered
Joined
·
159 Posts
Discussion Starter #10
do you have a test light? most of these questions you will be able to figure out if you do. the 12 v keyed on wire is probably just for the light. an easy source for this is your heater wire. or you can attach it to the acc post on your ignition switch. best thing is test with the light and verify the power goes off when the switch goes off.
Yes, I bot a test light the other day. Not sure if / how I can use it, as I believe I'm seeking a 12V source in RUN mode. Not "just" Accy, and not Start, and not always Hot.

Done a ton of work on engine (incl new cam, heads, etc); yet to fire her up initially. So may have to fly blind :blink: for the 30 min break-in run. Or would this test light come on briefly on a circuit that is 12 V in RUN mode when just bumping the starter over? Is bumping the starter, "RUN"? I'd be willing to try that a couple of times.

As I recall, the 12 V keyed ign power is for the elec choke, Tach, Voltmeter and Fuel Level gauge.

Anyway, just hate guessing at this elc stuff.
 

·
Registered
Joined
·
1,239 Posts
Yes, I bot a test light the other day. Not sure if / how I can use it, as I believe I'm seeking a 12V source in RUN mode. Not "just" Accy, and not Start, and not always Hot.

Done a ton of work on engine (incl new cam, heads, etc); yet to fire her up initially. So may have to fly blind :blink: for the 30 min break-in run. Or would this test light come on briefly on a circuit that is 12 V in RUN mode when just bumping the starter over? Is bumping the starter, "RUN"? I'd be willing to try that a couple of times.

As I recall, the 12 V keyed ign power is for the elec choke, Tach, Voltmeter and Fuel Level gauge.

Anyway, just hate guessing at this elc stuff.
Light will come on briefly in start position. With key in run position, light will stay on and go out when switch is turned to off. You almost have it down. What year do you have? See if I can find the right color for you.
 

·
Registered
Joined
·
159 Posts
Discussion Starter #12
Light will come on briefly in start position. With key in run position, light will stay on and go out when switch is turned to off. You almost have it down. What year do you have? See if I can find the right color for you.
'73 coupe. Avatar is a pic of her.

Yes, I can understand the test light staying ON in RUN. Just was hoping to have the Tach hooked up before I Run her the first time.

Thanks again!
 

·
Registered
Joined
·
1,377 Posts
I may be wrong and please correct me if I am. but I have installed many tachometers and for the red wire I just use any 12v key on wire and they have always worked fine. the white wire for the lights is wired separately if you want to be able to dim the light and have it turn on with the light switch. but I think that you are worrying to much. just find a 12 v key on wire and hook it up. unless the instructions specifically say something different that is the way I have always wired them.
 

·
Registered
Joined
·
1,377 Posts
I reread this thread and I think I am now better understanding your concern. basically you don't need a wire that is only hot when the engine is running, you need a wire that is only hot when the key is in the run position. so again use your test light find a wire that is hot in the run position. turn the key off and then to acc. if it stays off you are good to go. but basically the gauge will work even if you wire the red wire directly to the battery. it will just still have juice running through it when the key is off. so it is best to have it wired to wire that is only hot in the run position. I reiterate however for purposes of starting and testing the engine any 12 volt hot wire will work.
 

·
Registered
Joined
·
159 Posts
Discussion Starter #15
OK, thanks. I think the fog is starting to clear. I like the idea of using any 12v just for the initial start up. Could just dangle a wire out the pass side over to the + batt...

As far as finding a wire, I've found plenty! I just thought perhaps someone could point out some of the various components that a 12V keyed Ign wire in Run would end up at and start from. Then I could pick one of those. But just for the start up, the any 12V wire (or just the batt) idea sounds great. Thanks!
 

·
Registered
Joined
·
1,377 Posts
well again the most useful answer I can give you is to look at the wires coming out of your switch I never can tell which wire is going where and I usually don't want to take the time to look it up on the wiring diagram so I use the test light. it is faster and easier. trying to find the one wire that is going to the windshield wipers or whatever is too much of a headache for this job. btw I believe the windshield wipers are a component that is only on in the run position.
 

·
Registered
Joined
·
1,239 Posts
Diagrams don't go up that far, but green with red stripe leaving the ignition switch is power to voltage regulator for any of the earlier years I have ran into. Yeah, if your new engine has a flat tappet cam, you really need the tach, oil pressure and temp gauge. I have a set of mechanical gauges I use to at least breakin the cam. Good luck with your turn up.
 

·
Registered
Joined
·
159 Posts
Discussion Starter #18
Diagrams don't go up that far, but green with red stripe leaving the ignition switch is power to voltage regulator for any of the earlier years I have ran into. Yeah, if your new engine has a flat tappet cam, you really need the tach, oil pressure and temp gauge. I have a set of mechanical gauges I use to at least breakin the cam. Good luck with your turn up.
Yes, Flat Tappet; no roller block here. Really don't want to guess "by sound" where 2,200-2,500 or so is... And yes, as many of the new AutoMeter gauges are mech as possible. Tach and Volts I guess are the exceptions. Fuel level too, I guess. Those are the three, plus the + from the elec choke on the side of the new Edel carb, that all want this 12V + keyed Ign source...

I have a Grn/Red stripe that I'm no longer using, as I went w/ a one wire alternator and tossed the voltage reg as a result. So that would be a good choice? And it heads back to the Ign switch? I'll have to open up this test light and get upside down! Thanks again. :bigthumbsup
 
1 - 18 of 18 Posts
Top