Ammeter Wiring

[D Yaros]

Here is my situation:

I am attempting to install an SW -30 -0- 30+ ammeter in the engine bay of my 63 Monza.

Yes,I have heard all the cons to such a project, and do in fact also have a volt meter instatlled in the engine bay.

1) I have placed the ammeter in series between the batt and the voltage regulator. The needle simply does not move.

2) I have placed the ammeter in series in the starter solenoid circuit. The needle does not move.

3) In both locations I have tried a second ammeter, thinking one may be defective. The needle simply does not move.

When I say "the needle simply does not move," that applies both when I turn on the lights with the engine off, and when I run the engine.

The ammeter does have continuity between the two posts.

I am getting a reading of 21 amps off the the F(ield) and A(rmature) terminals of the generator. I get the same reading off the F(ield) and G(enerator) terminals of the voltage regulator. The volt meter shows 11.?V when the engine is running.

The car starts and runs fine whether the ammeter is wired in, or taken out of, the circuit.

So what I am I missing here? Why does the gauge not give any reading? Whatever the problem is, it is beyond my powers of deduction. I would appreciate any insights. Thanks!

I might also ask, how is the fuse block underneath the dash attached? In looking at it, I noted a lot of corrosion which could stand to be cleaned, but I can't figure out how to get the fuse block out to work on it.

[F&J]

The problem is that the meter needs to be "inline" with both the feed wire to everything except the starter, plus inline with the wire that charges the battery.

Good luck sorting that out

Not being a wiseguy, it just may be very complicated to do.

[MCHinson]

I would think that looking at a very basic wiring diagram for a car without many accessories would help you understand how to wire up your ammeter. Here is a wiring diagram that I found online for a Model A Ford. Perhaps if you print it out, you will see how Henry Ford did it. I think that might help you understand how it needs to be installed in your car. Good luck.

http://www.geocities.com/jim_mason_49913/wiring.html

[Guest simplyconnected]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: D Yaros</div><div class="ubbcode-body"> ...1) I have placed the ammeter in series between the batt and the voltage regulator. The needle simply does not move.

2) I have placed the ammeter in series in the starter solenoid circuit. The needle does not move.

3) In both locations I have tried a second ammeter, thinking one may be defective. The needle simply does not move.

When I say "the needle simply does not move," that applies both when I turn on the lights with the engine off, and when I run the engine.

The ammeter does have continuity between the two posts.

I am getting a reading of 21 amps off the the F(ield) and A(rmature) terminals of the generator. I get the same reading off the F(ield) and G(enerator) terminals of the voltage regulator. The volt meter shows 11.?V when the engine is running.

The car starts and runs fine whether the ammeter is wired in, or taken out of, the circuit...

</div></div> Wow, where do I start?

* First of all, 30-amps is ok for the old generator outputs, not modern 55-105-amp alternators.

* When an ammeter fails, the movement may burn out, but the separately built-in shunt will still continue to conduct. It is simply a very low-resistance 'bypass' that shares proportional current with the meter movement. They are NOT in series.

* What are you measuring 21-amps off the Field with??? This ammeter, or some other device? 21-amps seem awfully high for a field winding.

* A running generator should produce 14-Volts at or above 1,500 rpm. Below that, the generator isn't going fast enough to produce any voltage, but your battery still feeds the Field Windings, causing a DISCHARGE.

Dave, if you are putting your ammeter in series between your battery feed to your regulator, and the regulator terminal, you should see charging and discharging, IF your generator is putting out. Be sure to use #10AWG stranded copper wire and good CRIMP lugs. All your connections MUST be tight.

I hope this helps. - Dave Dare

[D Yaros]

Dave,

As much as I hate to say it, I am beginning to suspect the generator. This is because my volt meter is producing a reading of less then 12V, not 14.

You ask what I am using to measure the generator output. It is a V-O-A meter. I placed the leads across the F and A terminals on the generator. I got an actual reading of 7, which I multiplied x 3; as I was on a 10 Amp scale and the generator has a 30 amp capacity. Perhaps it was in fact only 7 amps?

I did in fact use 10 gauge wire, with solid connections.

[F&J]

When using a test voltmeter, go right to the battery terminals.

A charged battery should show 12.5v with the engine not running.

If you run the motor and only have 12.5 or less, then you need to test the generator.

On most cars, you would disconnect all of the wires from the generator, then place the volmeter positive clip to the ARM/Batt lug, then use a jumper wire to put 12v to the field lug. That should cause the generator to "run wild" and show extreme overcharging (beyond the normal 14.2v), as you race the engine. On some cars like old VWs, the field lug needs to be grounded instead of powered with 12v. I am not sure on your car, so look at a motors manual, etc, for the correct Corvair generator test.

When jumping the field lug, just jump it only long enough to do the test. If you leave it hooked up too long it can damage the generator. You only need to see the voltage spike beyond 14.2v, then unhook it quickly. You don't need to see if the volts go wilder than that.

So, if you find that the generator does run wild on the test, then you need to check the regulator as well as test each regulator wire for proper functions in case there is a broken wire, or even maybe not hooked up correctly at some point in the harness by a previous owner.

[Guest simplyconnected]

Dave, I assume you are testing a GM setup (because you show three GM cars). This may be a dangerous assumption, that's why I gave generic ammeter instructions in the last post.

Generators must produce more voltage than the battery in order to charge, that's why the regulator starts cycling (topping-off) @ 14 volts.

F&J is right, some regulators GROUND the field, and others FEED the field to excite it. This is where I have to be careful, in 'turning on' the Field manually. Most major auto parts stores will identify and bench-test generators & alternators for free.

Honestly, I never heard of multiplying between F and A, maybe I'm learning something new, here.

At home, I use an old headlamp to test; I get a visual, and I'm using a real load. I connect one headlamp lead to gnd, and the other lead to the bare Armature post on the generator. Be careful not to over-rev because an unregulated generator will produce MUCH more than 14-volts and will burn out the headlamp. (You can see when it gets too bright.)

I suspect your add-on ammeter is shot. Once you get the generator going, you can re-test it.

Dave