Actually you guys are both right. The alt lug iscwire directly to the starter which is wired directly to the battery. The only diff is there's a fusible link between the alt and the starter. There is no difference unless you had a 68 alternator that needed a separate voltage regulator then the alt output would be unregulated

 

Hey Scott-

Yes- but not really "directly" as the wire runs from the alternator to the horn relay then from there around the fender back along the firewall then through a fusible link (and even smaller wire) to the starter- then to the battery.

My point-
say the alternator doesn't ramp up to the current required to get the fans spinning (at idle)- the current has to flow from the battery through several connection points (6 or so) and small wires-you'll get a voltage drop AND the fans require MORE current at the lower voltage. The stock wires even brand new were NOT designed to handle that amount of current.

It's just not a good idea-

Chevy Chase figured that out....

 

No they don't.

Personally, if the alternator is 100A and the accessories will draw or supply 100A then I want ALL parts of the circuits that feed those accessories to be rated for 100A. Tapping off the alternator so you can leave the rest of the power wires under sized is just half assing it.

For certain C3 owners - the charging wire passes through the bulkhead connectors on some years of C3's. I certainly wouldn't trust those connections into the interior handling 100+A of current.

 

Fixed it

 

No, still wrong.

 

Richard....

An ammeter is a device that measures current flow. It doesn't matter that the 'instrument' being used as the gauge is a galvanometer. The current flows thru a current shunt...in this case, a length of wire in the main wiring harness...and provides a voltage drop which is proportional to the current being passed. The galvanometer is scaled in amperes; thus an AMMETER.

How many other ammeters use a current shunt? Oh, the vast majority of those gauges scaled in 'AMPS'.

It's an ammeter, Richard.

 

An ammeter does NOT show the direction of the current just magnitude....A galvanometer shows direction ..An ammeter is more accurate

 

Every DC analog ammeter I have ever seen was built using a galvanometer measuring the voltage across a current shunt. Makes sense considering that's about the only way you can make them. Most have the shunt built into the meters, but the way GM did it was to put the shunt remote from the meter.

I have also never seen a DC ammeter that did not display the current as a positive or negative current. AC meters measure as a magnitude only, but there is no direction with AC.

 

OK- like I said "technically" speaking - the Corvette C3's ammeter -is a galvanometer- as the definitions between the two verify ..It was sort of a tongue in cheek comment... If I had called it an ammeter- somebody would say its a galvanometer....

Just like a Kleenex and toilet paper to me- are interchangeable- but not to my wife!!! Agree to disagree.....

What I tried to do-

draw an easy to understand diagram of what I felt was a better way (not the ONLY way) to wire the car to solve the problems at hand. And offered other solutions to overcome issues.

I have done this more than once...but does that make me and expert- not really- but no one else came to the table and explain what they felt was a better way. So I'm all ears.

Richard

 

The analog meter mechanism/movement inside pretty much every analog meter made could be called a galvanometer since they are all based on the same operating principle. The configuration of the whole meter to read a useful value makes it into the type of meter. In the C3, it's configured to be an ammeter by using a remote piece of wire as a current shunt.

So, you could argue that only the meter portion in the cluster by itself is a galvanometer. But, you could also argue that the shunt needs to be included before it's a useful meter at which point it's an ammeter.

I personally would not run the fan wire to the battery. It's a wasted effort running a 10 gauge wire that distance when you already have a much heavier gauge wire running from the battery to the starter solenoid.
So, run a new charge wire from the alternator to the solenoid, protecting it at the solenoid end. Run a wire from the solenoid to a new accessory terminal block protecting it at the solenoid end. Both wires should be around 6 gauge. Connect the remote sensing wire from the alternator to the solenoid, protecting it at the solenoid end. Your fans and other other new high power accessories are powered from the terminal block.

There is nothing wrong with fusible links. They are simple and robust. Almost every GM produced since the 60's has fusible links protecting the main wiring. How often do you see dead GM's on the side of the road because a fusible link failed?

 

Geese- the ammeter- first it's called meaningless- then it the best and only way-if you know how to read it....

I refereed to the voltmeter- as a simple fix- as no one offered how to change/upgrade the wiring and then have the ammeter accurate- so the point was- doesn't matter- when the 'ammeter' becomes inaccurate you can call it whatever you want...totally misunderstood...





My reasoning to wire it an extra 6 or so feet to the battery- easy access to the fuse. Same as with the alternator - fused at the battery- easy access and protects the whole car.

And yes- that's how I suggested before how to wire if you were adding more than a fan-

Fusible links- There are several members (myself included 35 years ago) that have had a tow home thanks to burning one up. To me- it just makes sense than being on the side of the road waiting on a tow truck.

Richard

 

Thanks for the help.I checked the current at the ammeter wires and only got 4 amps.Where does this current come from.It should be 12,right?
I got the four amps running and off, with the switch on..The alternator is putting out 13.5 at the terimals ,on the alternator

 

OK- the voltage at the ammeter should be about 12.5V on both wires-

To check the wiring- disconnect the ammeter-Set the multi meter on DC voltage- touch one lead of the multimeter to one of the wires (black/white or black wire) and the other lead of the multimeter to a ground- should see about 12.5V - then test the other wire - should be 12V there too..

If one side or both shows no voltage- there are fusible links on each end (20 gauge orange colored ) - then more than likely you have burnt one. IIRC the black wire comes from the firewall connector and the black/white comes from the starter terminal.

If you see 12 V on both wires-
Test the meter- put the meter on Ω and put one lead on each side of the meter's terminals (disconnected)- if it reads nothing- the thin wire in the ammeter is broken.

Let us know what you find-

broken ammeter wire- internally

 

Ok
You were right,I got 12.7 in each one with the switch on.I connected a new replacement ammeter to the wires and it worked.However the after market amp gauges won't work and they are new.
Thanking you in advance for you help

 

The GM gauge uses the charging wire as the shunt and the 2 leads connect from it to the meter. The aftermarket gauges have the shunt mounted on the back of them, They'd probably work if you removed the shunt from them, but they wouldn't be calibrated so the scale would be wrong.

The reason you're killing ammeters is because you're drawing more current through the circuit then it was designed for. You could install heavier wires and leave the meter connected, but that would make the scale wrong. The direction of the deflection is all that would be important.

 

I dont know if im reading this wrong but you do not want every circuit to be rated for 100a that would be silly.. you want the main wires going from the alternator to the battery to be rated for more amps if the battery is where the circuits are being fed from but thats it really... The rest of the circuits are all designed to handle what they are wired and fused for.
It not different than houshold wiring... the main might be say 100a and the mains are fed with say 0 gauge wire but of course all your smaller 20 and 15 amp circuits coming out of that panel and fed from that panel have 14 or 12 awg wire and are breakered accordingly.

 

That is what I do. I have a 140A alternator to support the EFI, dual fans, 340lph pump, etc. I added additional charging line direct from the alternator the battery (with a fusible link). Used to fully peg when fans came on. Now, it barely moves. Enough for me to see that fans are running which is all I care about. The numbers are meaning less. Gauge behavior is the key.

Personally, I will probably swap to a voltmeter when I get motivated to pull the clock and replace with oil temp gauge. Just need to find a temp gauge that I like.

 

Yes, you are.