I just rebuilt my alternator and upgraded to 90 amps to keep up with my radiator fans. Does anyone make a voltmeter that looks like a stock c-3 ammeter? Is it ok to run that much amperage through a stock ammeter?

 

The ammeter only senses voltage change, it doesn't have the amperage pass through it like a typical ammeter does.

 

Is the ammeter around 25 to 30 with headlights and fans running?

 

That sounds about right, the fans are probably drawing in the niegborhood of 20 Amps, and the lights about 5.
you could take the fans out of the ammeter loop if you were so inclined. You would have to hook the power wire for the fans (Fused would be needed) to the + batt cable at the starter.

 

I have been running 25-30 for a year with no meter failure. My dual spals are wired directly to the Starter positive lug.

 

Looks like I was wrong on the way to bypass the ammeter. please disregard.

 

The ammeter is not the problem...it is only a millivolt meter which uses some of the wiring harness as a current-shunt to "measure" the current in the main line. The area of concern is the wiring harness itself. If you have "continuous" current loads of more than about 40 amps, you run the risk of burning out fuse links/related wiring. If you put the alternator in for a sound system upgrade, I doubt that you will pull too much continuous current; if it is for some other load that is somewhat constant, you probably will burn it up.

If you see the existing ammeter "pegging out", you need to rethink how to upgrade the wiring system as well as the alternator and ammeter system. You don't want to end up like some C3-er's with a fire in the engine bay.

 

25-30 is far from pegged out. If you are going to run electric fans then you are going to have the load. I am saying the gauge itself will hold up long term on loads BELOW 40 amps. It is simply a choice we make when we go to electric fans.

 

You are looking for a mid 80's chebby/maybe GMC pickup with full gauges in it, the voltmeter has slightly differant printing on it, but looks good, and it takes a sharp eye to tell any differances....

it's what I did....

all you do is take the two black wires and tie them together, then attach them to the + side of the VM, and of course ground the other peg....

 

If you power the fans from the alternator, the current drawn by the fans will not go through the ammeter. The ammeter shows current into and out of the battery. When the battery is fully charged, and the current draw by the car's electrical loads is less than the max output of the alternator, the alternator will power all of the cars electrical loads and the ammeter will read 0 amps.

 

Just use a voltmeter from a '76L-82 Vette. Bolts right in. You have to tie into a pink wire to get a voltage signal and tie the black ammeter wires together. Use an early orange needle if you get a later one with a white needle. That's what I did. Works like a champ. You can get them from the usual suppliers, Ebay, Corvette Clocks by Roger....

 

Current doesn't flow through the ammeter, boys. It only flow through the wiring. The shunt in the wiring harness generates a small voltage that the "ammeter" reads and converts to "amps" only on the dial face.

If your system is pumping a lot more current through it than it was designed for, the wiring will "pop"....not the gauge. Oh well, a blown fuse link or a fire in the engine bay will be your "message" to fix it, I guess.

 

I have a 105 Amp CS-130 alternator. I added an extra charging wire direct to the battery from the alternator. Big fat #6 gage with a fusible link. My ammeter still works but the needle deflection is a lot less since the majority of the charge now flows through the new wire.

For example, when my 30 amp dual Spal fans kick in, the ammeter shows a 10-12 amp current draw. The fans get there power from the starter so the majority of the current is flowing through the new wire and then via the big starter cable to the fans. Works great.

 

No, the wiring will not "pop", all of the wiring on my car is brand new and I checked the setup with lectric limited (they built the harness), I think that I stated 30 amps max and that is a high point. The spals are fused and the amp gauge only gets a portion of the load as that part of the harness parallels anothe line that goes to the fusable links at the starter. I doubt that I would ask you for advice if I had a blown link, I would go to the people that build wire harnesses for a living.

Durango boy, you want to jump in on this?

Somone mentioned coming off of the aternator terminal for the fans, I was told by the spal engineers not to do that but to run directly to the starter lug or the battery.

 

SteveG75: That was a good move on the extra wire when you have an original harness. Great idea on the fusable link. Give me a shout if you ever have that car in Richmond, I would love to see it.

 

Let's see.... now you say the "extra wire" was a good idea. What the heck do you think I've been trying to tell you? {I give up.}

 

I don't understand why you would connect your fans directly to the battery (or big lug on the starter - same thing). All of the electrical loads in the car are powered from the alternator, most notably large loads such as AC fans and headlights. I think M.A.D Electrical has a good article about this (don't know if MAD still has his webpage - he was having health problems). Why not power the fans from the alternator just like everything else?

The battery is connected to the alternator by a wire with some resistance, it's a fusible wire. Current going to, or from the battery, creates a small voltage across this wire. This small voltage is "read" by the ammeter. The sense is that a small positive voltage causes the ammeter to read + amps and small negative voltage results in - amps. Although the ammeter is calibrated in "amps" its really a voltmeter reading the volts across the resistance wire (fusible link).

If you power your fans from the battery lug, the current they draw is coming from the alternator (otherwise the battery would go dead pretty soon). This causes the ammeter to read a "charge" current, when the battery is in fact not charging. The ammeter is now reading the current going to the fans. This is OK, but I thinking you're stressing the resistance wire (fusible link). You don't want this to ultimately blow open.

When my fans run, the ammeter reads 0. Also, I don't need a ammeter to tell me my fans are on. I can hear them, even over the sound of the factory sidepipes.

 

Try reading again there bud:

"That was a good move on the extra wire when you have an original harness"

Even still, any original harness is designed to take over 30 amps. How many amps do you think your alternator would put out if you jump started a dead battery?

 

Never read the Mad article, I simply had to rely on the spal engeneers, they told me the fans would pull off of the battery during idle which would in turn help the fans last longer. They also suggested a larger alternator but I have not gone there. I have run over 5000 miles without a problem and the spalls are a nessassary evil given the engine that I am running. I understand an amp gauge reads actual amps not small voltage. There is a parallell circuit via the dash harness that sends power through the amps gauge.

 

I couldn't at first imagine why the Spal engineers would say this.

After some thought, I think I may have a possible answer. It involves the resistance wire that runs from the alternator to the battery lug on the starter (it's the wire that routes alternator charge current to the battery and battery current to the loads when alternator output is insufficient).

Lets assume you've got all electrical loads on; headlights on bright, AC fans on, stereo on, etc. and you turn the engine off. Now all current required comes from the battery and flows through the resistance wire (fusible link). Now a large current is flowing through the wire. The factory sized the wire to withstand this current. I think someone said it was rated at 30 amps. Now, if you have the Spals connected to the alternator, the Spal current will also come from the battery through this wire. Say the Spal takes 20 amps. Now you've got a current that could exceed the current max for the resistance wire (fusible link). This could cause the wire to fail. For example, your car loads might be 20 amps and 20 extra amps for the SPAL (connected to the alternator) would result in 40 amps, exceeding the 30 amp rating of the resistance wire.

Anyhow, my 68 doesn't have AC, etc, so I think I still keep by fans on the alternator. I like the idea that the ammeter reads 0 when the fans are on.