Wiring of Ammeter on 66 IIA pos grnd

[Cosmic88]

my question is what is the proper way to wire the Ammeter (within the fuel, ammeter, high beam cluster) to show both alternator output current (when the engine is running) and draw against the battery (when the engine is off). First of all, I am fixing P/O wiring, so keep that in mind. The P/O had the alternator output wire leading up to a fuse block, not to the battery as one would expect. I have corrected this which led to having to rerun most connections for lights and such.

Second detail to keep in mind, I have the original positive earth harness on this truck with no voltage regulator. No need for a regulator as the alternator has an internal regulator. I have a "one wire" alternator with the output post connected to the batt. there are two additional wires from the alt... one is the exciter wire which I have jumped from the output post... a sort of self-exciting circuit and the other wire leads to the charge warning light in the dash.

In the original wiring diagram the ammeter calls for three input wires... one from the starter switch circuit, another from the inspection socket and the other from the voltage regulator.

Best way to wire this sucka???

Thanks all...

[scott]

not sure but if ya got two big wires connected to you ampmeter be careful. i replaced my wimpy lucas alt with an ac delco 80amp and all the smoke escaped from my meter. i'm running a volt meter now and am replacing the amp with a 2nd fuel gauge for my aux tank.

[Cosmic88]

there are two large (larger than normal) female connectors. One on each side of the ammeter... how'd you fry it? I have connected one side of the ammeter to the output post of the alt. and that gave me a positive output reading but no draw reading when the engine is off....

[scott]

i've a dual battery set up, no problem but the truck sat for a while and when i fired it up the alt's internal regulator sensed the need for higher output to charge the bats. so it was putting out more amps than the ampmeter could handle. the ampmeter is wired in series so all those amps going to charge the bats ran through the ampmeter and toasted it. i just connected the 2 fat wires together, wrapped w/ electrical tape and motored on to autozone and got a volt meter.

[Cosmic88]

How exactly did you have the wires connected? Did the meter show negative draw (engine off) and positive amps (engine on)?

[scott]

to be honest i don't remember if a draw with the engine off was being read. mine was a wiring mess (50 years of folks messing w/ it). since i've rebuilt my motor i've not completely installed the new loom. i hooked up just enough to start and run the motor. no idiot light or any kind of lights for that matter yet.

[carl k]

When I wired my '67 (negative earth) truck for a Chevy engine, I ran one wire from the 63A 10SI alternator B+ terminal to the positive side of an aux. Smiths 50 amp ammeter. I took another wire from the unswitched side of the fuse box to the ammeter positive. Then a single wire from ammeter negative to the starter solenoid/battery. If getting two wires onto the ammeter + is difficult, they could also be joined at the fuse box. The other two wires at the alternator I connected as you have.

This setup shows both charge and drain.

Carl K.

[Cosmic88]

I am assuming you had two wires coming off the B+ (battery output) post??? One directly to the battery and the other to the pos. side of the ammeter?

[Andrew IIA]

The ammeter on my '63 SIIA (neg. ground) is disconnected. The highest reading it has is 30 amp and I have a 63 amp delco alternator - if it were connected it would be pinned to the top all the time, and might well get cooked. So, its disconnected.

Best regards, Andrew

[Cosmic88]

I also have the original +30 / -30 amp gague and have the 63 amp delco alt.

I'd only get 63 amps of output from that alt. if I were drawing that much. I don't have a winch so I won't be exceeding the +30 amp max of my gague any time soon. Unless your battery is dead you shouldn't see much output on the gague and certainly not pinned.

[Andrew IIA]

I also have the original +30 / -30 amp gague and have the 63 amp delco alt.

I'd only get 63 amps of output from that alt. if I were drawing that much. I don't have a winch so I won't be exceeding the +30 amp max of my gague any time soon. Unless your battery is dead you shouldn't see much output on the gague and certainly not pinned.

Good point. Electronics not my strong suit

[carl k]

Cosmic88-

No, just one wire on the alternator B+ terminal. When charging, current goes from alternator, through ammeter, to starter solenoid/battery. When drawing current, current passes from battery/starter solenoid, through ammeter, to fuse box, to load. Ammeter shows current flow for both conditions.

I should have mentioned I put fusible links at both the alternator connection and the starter solenoid/battery connection.

Carl

[greenmeanie]

Wiring in an ammeter as described makes your entire electric system dependent on the reliability of the gauge which, if you do let the battery go flat, may be pushed far harder than originally designed. This was known for creating a lot of problems on Dodge vehicles back in the day. A voltmeter tells you more about the state of your charge system and can be run in parallel so it has no effect on reliability.

Here's a good explanation.

http://madelectrical.com/electricaltech/amp-gauges.shtml

[Nium]

Lo

Carl K,
You may want to remove them fusible links. I believe I fried an alternator when 1 of the links broke (the alternator one) which led to a 0 Volt condition on the alternator which caused it to fry by trying to bring the load voltage to 12 VDC.

Cosmic 88,
Wire the ammeter in series with the wire you want to monitor. If ya wire it in series on the alternator output wire you'll get what the alt is putting out to charge the battery. If you turn off the ignition and leave the headlights on I don't think you'd be able to see the draw 'cause the current would flow from Batt->Fuse Block->Lights for example. If there are three posts then I would guess the odd one out would be the ligthbulb, maybe? The body of the gauge would provide the path to the frame or pos side of the battery thus 1 wire for the bulb on wire diagram.

Generally speaking an ammeter is spliced in series with the wire that you want to monitor the current flow in. So, if you wire it to the output of the alternator you'd have to run that wire thru the firewall unfused (unless you use a self-reseting circuit breaker; hard to find) to the ammeter then back to the battery, kinda a fire hazard. Maybe wire it to the wire from the battery to the ignition switch. That should tell you the current draw of the electrical system and you could fuse it without havin to worry 'bout fryin the alt.


Alt--->(Ammeter)--->"-"Battery"+"--->Frame
(to monitor alt output)

Best o Luck
Walker

"Ronnie" 1968 Series IIA, 2.25L Petrol, Neg. Earth