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Add-on reversing lights are popular now....as they were 'back in the day' before all cars had them as standard issue. From the packaging i'm guessing 60s-70s vintage?
It is an aftermarket reversing light. back in the 1960s and early 1970s, most cars did not have them, so you could add one with a dashboard switch if you wanted to have one. I clearly remember them...
Not sure how you would wire this up even though there is only one Wire
Another aftermarket scoop OB. By the by, I think that the wipac could be worth something, as lolts of people want period stuff for rebuilds etc.
An ammeter, says I anyway, is far more useful than a voltmeter. The reason they are almost never fitted these days is because to measure the amps, the entire current load from the main battery cable has to go through the ammeter; which makes wiring it into the dash both costly and even dangerous. The wire you see is the illumination; there should be two screw terminals for the main current load.
I am open to correction on this, but I would have thought it would be possible these days to have something digital in the main cable with a sender only to the dash, as knowing the amps is far more useful than a voltmeter.
An ammeter, says I anyway, is far more useful than a voltmeter. The reason they are almost never fitted these days is because to measure the amps, the entire current load from the main battery cable has to go through the ammeter; which makes wiring it into the dash both costly and even dangerous.
I've worked on a number of older cars with burned ammeter wiring. Mostly old Chrysler products but others as well. Not good!
A lot of older USA cars had a 'shunt' circuit ammeter. Only a sampling of current, not the full electrical load, passed through the the instrument.
As for usefulness, I have no preference....but voltmeters are certainly easier to contend with in terms of wiring, IMO
The last car I had that included an ammeter was a 66 Ford Mustang. I miss them.
And, way back in 46, my first car, a 23 Ford T only had one instrument on the dash, an ammeter.
Odd uses early on:
1. My friend Billy lost the key to his T. Well, the ignition switch was always on. So, Billy a smart gu7y in many ways merely killed the engine with the choke or against a curb. Then if needed, cranked the engine just a tad til the meter showed O. Points open, no discharge!!!
2. Early old cars had no accessory position on the ignition switch. So, if any of us got lucky and found a gal to park with, we wanted music from the car radio. OK, just bump til the ammeter was 0. Key on, have fun. Extra caution, park on a hill. Early radios ate amps! Might need a start from coast Gals not favorably impressed with having to push.
I wonder if I have an old ammeter in my of stuff....
The last car I had that included an ammeter was a 66 Ford Mustang. I miss them.
I owned a '66 Mustang as well...and still work on them all the time, including just this week, in fact! They had the shunt-type ammeters; rarely operational these days unless they've been replaced.
All current measuring devices are SHUNT even the highend reference multimeters. They read the voltage across a resistor, accuracy is dependent on the quality of the resistor. Simple ohms law I=E/R.
All current measuring devices are SHUNT even the highend reference multimeters. They read the voltage across a resistor, accuracy is dependent on the quality of the resistor. Simple ohms law I=E/R.
Thanks for the correction; I've obviously confused the terminology. But, whatever it's called, a lot of the old ammeters didn't carry the full electrical load but just a portion of it...or something like that?
Now your mucking about in my neck of the woods. Yes these old ammeters have to "see" all of the aux current to and from the battery. Yes there's a shunt, it's just built into the case of the meter. So on your old Mustang, 30 amps was it, so a 10 guage wire from the battery, to the ammeter, out to the junction of the power to the fuse box and the alternator.
Now 30 amps won't even run the radiator fan.
Most meter movements are 50 MilliAmps full scale and then bump the resistance of the shunt around depending on how many amps the meter reads at full scale.
Long winded, sorry.
Steve aka 71 MKIV
91 Jaguar XJS convertible classic edition
71 Triumph Spitfire
"never underestimate the perversity of an inanimate object"
Now your mucking about in my neck of the woods. Yes these old ammeters have to "see" all of the aux current to and from the battery. Yes there's a shunt, it's just built into the case of the meter. So on your old Mustang, 30 amps was it, so a 10 guage wire from the battery, to the ammeter, out to the junction of the power to the fuse box and the alternator.
No, they were wired with light gauge wire....maybe 16 gauge?
Here's a cut-n-paste explaining the Mustang ammeter wiring for your review and comment.....surely better than my bollixed up effort !
"If they are talking about the ammeter wiring for the '66, then the wires can be left open. Some of the discussion on the other forum is correct, in that an ammeter is normally wired in series with the load in order to measure the current. However, what the ammeter on the '66 is not a simple series circuit. The current that is being measured is the current through the black/yellow wire that ties the output of the alternator to the battery via the starter relay terminal. If you look at the wiring diagram and trace the pair of wires that go to the ammeter, one side is connected to the alternator output and the other to the starter relay/battery post. However, those two points are ALSO tied together with the black/yellow wire. If you assume that the black/yellow wire is a perfect conductor, then there would never be any current flowing through the ammeter wires. That wire is NOT a perfect conductor, there is some resistance in the wire, just as there is some resistance in the ammeter coil. What is created is a parallel circuit where the ammeter coil is in parallel with the resistance of the black/yellow wire between the alternator output and the battery. The reason that the ammeter is wired in this way is that there can be significant current flowing between the alternator and the battery, 70 or more amps, and it would not be desireable to run a pair of heavy wires all the way from the alternator, through a dash mounted ammeter (that could directly read 70+ amps) and back to the battery. So what they have done is to shunt a small, proportional amount of current through a cheap low current ammeter to give an indication of the magnitude and direction of the current flowing in the black/yellow wire."
I think "...proportional current..." is what i was trying to express in saying a "sampling" of current.
I think some other American cars used a similar method. Chrysler products, though, ran the full system amperage right through the ammeter for many many years.
Interestingly, and new to me, is that 1965 Mustangs used an 'inductive loop' ammeter....no wiring connections at all. Apparently the wire just an along the backside of the instrument case and the needle reacts to a magnetic field!
Oh well, getting way off topic....but my curiosity got the better of me !
03-15-2018, 07:12 PM
Unboxing a Bygone
