1966 chevrolet ammeter

[samsonized]

wiring up my 1966 corvair with an external ammeter  and i have an ammeter question. i am going to run a wire from the battery + terminal to one side of the ammeter and from the other side of the ammeter to the battery terminal of the ignition switch. i am going to run a lead from the battery terminal of the ignition switch to the unswithed side of the fusebox and a wire from the igntion terminal of the ignition switch to the keyed side of the fusebox. assuming everything is off will the ammeter drain the battery. i am using an external regulated delco alternator with the hot lug of the alternator hooked to the hot lug on the starter through a fusible link.

[TerryB]

Sorry, I don’t follow your wiring description as well as I should but I can tell you that a basic needle pointer type ammeter is not an electric power consumer of any noteworthy amount.  The energy it needs to operate is derived from a very small amount of the electric current flowing through it when the circuit it’s in draws current.  If there is no current flow, the ammeter power use is zero.

Edited August 11, 2023 by TerryB (see edit history)

[samsonized]

The concern is whether the small draw that it does have over time will kill the battery. Also whether the alternator or regulator would have any draw 

[TerryB]

19 minutes ago, samsonized said:

The concern is whether the small draw that it does have over time will kill the battery. Also whether the alternator or regulator would have any draw 

If it is an analog meter, the kind with a pointer and “0” in the middle, it does not have any parasitic current draw to worry about.  A digital meter could be different.  When current flows in an analog meter a very very tiny amount of circuit current is used to move the needle off its 0 point to the point that indicates how much current is being drawn.  An analog meter can pretty much be thought of as just a piece of calibrated wire in the circuit.  On its own an analog current meter will not draw any current from the battery, it will only indicate when current is flowing.

Edited August 11, 2023 by TerryB (see edit history)

[samsonized]

Thank u. Still need an answer to the rest of the question 

[TerryB]

Like I said earlier, I can’t mentally picture you connections on the Corvair.  Under normal circumstances the alternator and regulator do not draw current when the engine is not running.  If they did, there would be lots of cars inoperable after sitting for short times.
 Today’s modern cars do draw current when not running to keep their the electronic gadgets happy and over time dead batteries are the result.  A common one is cars with keyless start as the car can be in search mode to see if the key fob is close by.  

[samsonized]

Thanks 

[Frank DuVal]

What are you trying to accomplish, not in wiring, but in operation of an ammeter?

 

You could just wire it in the red wire going to the HRPT (horrible red plastic thingy as it is called in the Corvair world). The HRPT is the red plastic terminal mounted just ahead of the battery on the frame rail where the smaller wire from the battery positive terminal connects to other loads, like the wire going to the firewall connector from the engine harness to the body harness. This would tell you if the battery is supplying power or being charged.

 

You can run 8 awg wire to and from a dash mounted ammeter from this electrical location. BUT, you will need to fuse the wires, as a short on these will quickly turn you car into ash.😧 

 

Many Corvair people place a 50 amp circuit breaker in that smaller wire from the battery positive to the HRPT. Chevrolet placed a fuseable link in that position on 67 and later Corvairs.

 

You can also get very good answers on:      corvaircenter.com/phorm     that is now a CORSA owned site.

 

And, once alternators came in sizes larger than 30 amps, ammeters went away and voltmeters became the defacto way to see if the system was charging or not. Voltmeter can be installed under dash or simply plugged into cigar lighter and tell you everything you need to know.

 

Edited August 11, 2023 by Frank DuVal (see edit history)

[samsonized]

Car has a custom harness in it 

[Frank DuVal]

Then just put in a voltmeter after the ignition switch.

[samsonized]

Ammeter in car already 

[Bloo]

5 hours ago, samsonized said:

The concern is whether the small draw that it does have over time will kill the battery. Also whether the alternator or regulator would have any draw

If the alternator is a GM one with an internal or electronic regulator, there is a very tiny draw. It is normal. Any draw will eventually run the battery dead, but so will the self-discharge of the battery. Only generators and old alternator systems with an electromechanical regulator shut themselves off 100% and have no draw. If the car is going to sit a lot, get a battery maintainer.

 

Also, that is not how ammeters work. They measure flow only. They have no draw of their own. For the rest of this post I am going to assume this is an aftermarket ammeter. If it is a stock 1966 GM ammeter, please post back because those are an odd setup and it changes everything.

 

The ammeter is to measure flow in and out of the battery. The electrical current flows THROUGH the ammeter on it's way to the battery.

 

Another not-so-obvious thing to keep in mind is that the source of current for all the accessories is the alternator, not the battery, when the engine is running.

 

Simple example #1, no ammeter: A large wire, probably #10 or larger, runs directly from the large post on the back of the alternator to the battery. On GM cars, this usually runs from the alternator to the starter post instead, and the positive battery cable completes the circuit back to the positive battery post. They may not have done it exactly like that on a Corvair because the engine is in the back, I don't remember, but the idea is the same. There is a big wire of some sort running from the large alternator post to the battery, maybe using the positive battery cable as the last section of wire, maybe not.

 

Simple example #2, aftermarket ammeter: Same as #1, except the big wire flows THROUGH the ammeter. That is, a big wire runs from the big alternator post to one ammeter terminal, and another big wire runs from the second ammeter post to the positive battery post. If GM used the starter post instead like they often did, you could run it there instead.

 

The ammeter only measures flow and does not need or use any kind of a ground.

 

One important detail: ALL the accessories get powered from the alternator side, not the battery side. The big wire could also land on an ignition switch or a light switch first and the on to the ammeter post. It often does on some cars with traditional ammeters, but the important part is that all the accessories are connected on the alternator side, not the battery side. It is desirable to keep as few splices or connectors as possible in this big wire as it goes on it's way to the battery. Any accessory connected to the "wrong" (battery) side will have any current it uses registered as a charge on the ammeter, making the ammeter horribly inaccurate. Don't do that.

 

One exception: Back when GM cars had traditional ammeters, they hooked the horn to the battery side of the ammeter.

 

Make high quality connections on the big wire. Solder them if you can. Any bad connection is going to get HOT. Make sure the big wire cannot get cut or pinched on it's way to the dash and back. Use grommets or whatever good cable management is necessary to keep this wire from harm. If the big wire gets grounded somehow, it will catch fire with all the energy of the battery behind it. A factory setup using a traditional ammeter would have probably had 2 fusible links, one at the back of the alternator, and another at the positive battery post (or starter lug). It would be a VERY good idea to do this.

 

For the reasons in the above paragraph, you usually see voltmeters today instead of ammeters on any factory jobs, and most aftermarket setups too. With a voltmeter, all you need to do is hook up a little wire and a ground. It's easy, and that's why the previous posters are suggesting it.

 

P.S. If an ammeter reads backwards, reverse the leads (it's just a flow meter!).

 

 

Edited August 12, 2023 by Bloo (see edit history)

[samsonized]

Thank u 

[Frank DuVal]

6 hours ago, Bloo said:

They may not have done it exactly like that on a Corvair because the engine is in the back, I don't remember, but the idea is the same.

So is the battery and alternator, just like a front engine car, everything right next to each other. 😁

 

Alternator big stud connects to HRPT (explained above, a junction terminal on frame rail) and a #10 red connects the HRPT to the battery positive post. No need to run all the way to the starter (another foot away ). All other loads connect to the HRPT, through the body harness, most through the ignition switch.

 

Bloo, your description of how to wire the ammeter is spot on!

 

There was no stock Corvair ammeter. There was an optional gauge package for the full sized Chevrolets, of which Bloo speaks, which hung from the middle of the dash, above the hump. I had one for years uninstalled (lack of car ) but then sold it.

 

Samsonized, Is this new wiring system a known entity (like Racers Inc. or such) or just a person with a few spools of wire? Did they move the battery to the front?