Ammeter Overcharging

[CHANMADD]

With that much current draw, I would take the Ammeter out of the circuit entirely. At this rate its going to overheat and be a fire hazard.
Don't forget , all that current runs through the Ammeter and those thin wires.
Also. If it came with a 40 amp fuse, I hope you have a relay in that circuit too.

[patrickt]

Originally Posted by CHANMADD

With that much current draw, I would take the Ammeter out of the circuit entirely. At this rate its going to overheat and be a fire hazard.

Or run a parallel wire with the ammeter circuit. I have a 12 gauge parallel wire with my ammeter circuit and it does two things: 1) It mutes the heavy draws of current when my fans come on, that used to send the needle all the way over to the left where it would get stuck, and 2) it dynamically re-routes current around the ammeter (which I really like) should the ammeter start to overheat. The ammeter still registers correctly, the readings are simply reduced. They don't, of course, reduce past the zero mark and give you an incorrect direction of current. But, it pretty much eliminates the possibility of the ammeter overheating because, as the ammeter heats up because of a failure, it creates additional resistance in that leg of the circuit and current will then just go down the parallel path (that's just Ohm's Law). Think of it like having two parallel wires, of equal gauge, running to a 120 watt light bulb, which will draw roughly ten amps. All things being equal, each wire would have five amps on it. On one of those two wires you have a 20 amp fuse, and on the other wire you have a one amp fuse. You will not blow the one amp fuse because, as the filament heats up, the resistance increases and the current then passes through the other wire.

[xb-60]

Originally Posted by patrickt

Or run a parallel wire with the ammeter circuit.....

Now that sounds simple. Did you come up with that solution yourself, or is that an accepted way of 'insulating' your ammeter?

I will be using a Smiths 30 amp ammeter on my 289, as that is what the original cars used. I was a little uneasy about using a 30 amp ammeter, but your method would help my ammeter cope quite safely.

Cheers,
Glen

[patrickt]

Originally Posted by xb-60

Now that sounds simple. Did you come up with that solution yourself, or is that an accepted way of 'insulating' your ammeter?

That's a pretty common way of reducing the current passing through an ammeter. Really high-quality, high-amp gauges don't need it, but I would not bet my car on the quality of one of these old Smiths gauges.

[xb-60]

I completely agree

[HighPlainsDrifter]

Hi,
The old cars with generators used ammeters, new cars with alternators should only use voltmeters. DC current is dangerous and if shorted or not wired correctly will BURN down your car. Most cars use 80 amps to run things;
electric fan 25 to 35 amps, lights, 8 amps, ignition 5 to 30 amps for MSD, heater 20 amps, etc 'that is why you have a 100 or 140 amp alternator.
The point is don't put all that through a 30 amp gauge, you can over heat and BURN your car down.
I have worked with DC in the phone industry for 35 years and have seen shorts arcing and welding big ironwork without blowing a 60 amp fuse.
Perry

[fastd]

Originally Posted by patrickt

Or run a parallel wire with the ammeter circuit. I have a 12 gauge parallel wire with my ammeter circuit and it does two things: 1) It mutes the heavy draws of current when my fans come on, that used to send the needle all the way over to the left where it would get stuck, and 2) it dynamically re-routes current around the ammeter (which I really like) should the ammeter start to overheat. The ammeter still registers correctly, the readings are simply reduced. They don't, of course, reduce past the zero mark and give you an incorrect direction of current. But, it pretty much eliminates the possibility of the ammeter overheating because, as the ammeter heats up because of a failure, it creates additional resistance in that leg of the circuit and current will then just go down the parallel path (that's just Ohm's Law). Think of it like having two parallel wires, of equal gauge, running to a 120 watt light bulb, which will draw roughly ten amps. All things being equal, each wire would have five amps on it. On one of those two wires you have a 20 amp fuse, and on the other wire you have a one amp fuse. You will not blow the one amp fuse because, as the filament heats up, the resistance increases and the current then passes through the other wire.

For those of us that don't know electrics as well as we should; could you explain a bit more granualarly how to run a parallel wire?

[patrickt]

Originally Posted by fastd

For those of us that don't know electrics as well as we should; could you explain a bit more granualarly how to run a parallel wire?

Different cars will have different "easy ways" of running a parallel wire. But remember, the goal is to have a shortcut path from the alternator to the battery without going through the ammeter. That said, the easiest way that will work on pretty much all forms of cars around here is to run a wire from the output terminal of the alternator to the positive terminal of the battery. Once you've grasped that concept, you can look at your car and say "instead of wiring it directly to the positive side of the battery, I'll wire it to the positive side of the starter solenoid that I can clearly see connects right to the battery." Likewise, you might say "instead of connecting to the output of the alternator, I'll connect to where the alternator output wire clearly connects to the fusebox." Each car will be a little different, but that's the basics. On an ERA car, connecting the alternator feed at the fuse box to the fused side of the 50 amp circuit breaker on the firewall is probably the easiest.

Originally Posted by fastd

I called holley. They say that the efi ecu pulls 6 amps but the fuel pump pulls about 15 amps; so 21 amps plus what the battery pulls would be my +25 or so.

They didn't entertain the idea of pulling power through the fuse box cause it could create "electrical noise"; I can see that with respect to the ecu but I think if I power the fuel pump through the fuse box I could solve most of my issue...thoughts?

OK, the ECU could be sensitive. MSD essentially says the same thing (run their box right off the battery), and most of us also run a big fat capacitor across the leads to filter out electrical crap like AC, spikes, etc. But I can't see how feeding a fuel pump from the other side of the ammeter would cause any harm at all. But, to be prudent, just run a 10 gauge test wire from the fuse box to your pump and see how it all runs before you make final wiring corrections.