two wiring issues I need help with.....please

[ShadowBolt]

I have just about finished working on my car. I ripped out all the wiring (I mean all of it front to rear), installed new harness and switch box, fixed the seat bracket, and installed new brake booster. All I have left is to hook up the O2 sensors, the fuel gauge and the volt meter. The O2 sensors should be easy. The new harness has the wires hanging down on the bell housing and I hope the wires will reach. I know the fuel gauge wire is yellow with a white stripe and I found it protruding out of the rear of the dash (the three inches I left). I ran a new wire from the tank sending unit up to the dash. I tried connecting just those two wires and it will not work since it must have some kind of power to work. I can't afford to power up the whole instrument panel since that could make a lot of the other cut off wires hot. The fuel gauge works like a ohms meter and like a ohms meter, must have a battery to work. Also I need to make sure I hooked up the alternator correctly. This was not part of the new Painful harness and I cut it all out before I noticed. There are three wires leaving the alternator (and attached regulator). Two go to the battery and the small wire goes to the volt meter (assuming I did it correctly). I don't know how to wire up the original fuel gauge and volt meter. If someone here knows and would share it would be a great help. I have thought about purchasing a new fuel level gauge and volt meter from Autometer. That would be the easiest way but the ones in the instrument panel would be fine with me if I can figure out how to hook them up. Ideas?


Thanks in advance,
JJ

[Adam Ginsberg]

IMO, don't sweat the fuel gauge. Get a handle on how much fuel is used for a given race length ( Eric should know this to the drop ), and leave it at that.

FWIW, my car didn't come with a fuel gauge, and I've never thought about putting one in. I've got a decent handle on how much fuel #5 uses for a given track/session/race, so....I stick with the KISS principle.

Sorry, but I'm no help on the voltmeter stuff either.

[donovan]

The charging circuit is a tricky one... I don't remember what I did to make it work, but it seems like I had to wire in a small resister into the line thru the gauge to make it charge.

DD

[ShadowBolt]

The charging circuit is a tricky one... I don't remember what I did to make it work, but it seems like I had to wire in a small resister into the line thru the gauge to make it charge.

DD

David,

Was that with the factory gauge or an aftermarket? I read that you must have a gauge or light or the system will not charge.

JJ

[Fbody383]

...but the ones in the instrument panel would be fine with me if I can figure out how to hook them up. Ideas?

Jerry, check with you regular mechanic and see if they have an AllData subscription. If they do, he would be able to print out the factory wiring diagrams for you.

I got a subscription for the Camaro because I'm cheap and new I would keep the necessary factory harness. The "amateur" site is www.alldatadiy.com.

Hope it helps.

[mitchntx]

The charging circuit is a tricky one... I don't remember what I did to make it work, but it seems like I had to wire in a small resister into the line thru the gauge to make it charge.

DD

I'm no sparky and certainly no Ford PooBah, but on a 4th gen, there is a wire that sends 12V DC TO the alternator as exciter voltage. It's gotta be there in order for the alternator to charge the system.

However, apply full amperage to exciter will eventually kill the voltage regulator. Hence the reason the circuit runs through the gauge cluster first.

So, a 10K (I don't think size really matters in this case ) ceramic resistor wired in series just behind the alternator will fill the amperage drop needed to keep from killing the regulator.

Also, be advised that this circuit needs to be broken when the cut-off switch is activated. If not and you could very well not be able to kill the engine because the alternator is feeding itself.

[donovan]

It has something to do with the gauge, factory or not, I have an aftermarket gauge and I needed it for make it chagre...

RP pointed this out to me when I was wiring my car...

It has something to do with the lead that has the dash light, and you need it in place to make it charge... and it has to have resistance. You can have a light in there but if the light burns out is stops charging, the factory setup has the light and resistor on it.

I don't have a light, just the resistor...

On the back of the stock gauge cluster you can see the resistor next to the gauge, its soldered to the back of the panel. That is how I know what one to buy.

DD

[ShadowBolt]

It has something to do with the gauge, factory or not, I have an aftermarket gauge and I needed it for make it chagre...

DD

I would have thought the aftermarket gauge would have had a resistor built in it.


JJ

[GlennCMC70]

a volt meter is easy, just get 12v from anywhere and it will tell you voltage the system has.
if its an ampmeter, best of luck.
there is probably a common 12v for the cluster that also puts 12v on the fuel guage. theres no way around it, if you want it to work, you gotta get 12v to it. i used an autometer in my car.

[GlennCMC70]

as for the voltage regulator and the light bulb and resistor deal.
the resistor is needed to regulate the current flow. i was told that w/ no resistance on the sence wire for the regulator field coil, the alt will just put out max volt/amp all the time. you want it to put 14v on the system.
max output will kill the alt (regulator). you also dont want the feild hot all the time. when the car is off there is no air flow thru the alt to cool the parts. w/ the field getting 12v and no air flow it gets very hot.