Are Mopar shunts a simply wire or a known resistance wire ?

I can't find any info on this and a friend from another board once measured and I THINK got 0 ohms ( it was long time ago ). actually the last time I got a shunt from a Mopar in hands really seemed to me a regular wire.

I have being playing with idea of the Ammeter shunt conversion on my 74 Charger using a 77/80 Lebaron ammeter, since is the same size, deepness and needle disposition. And got the led indicator which I think is a Low voltage indicator ? would need just to play with the face interchange and some other detail

http://www.forbbodiesonly.com/moparforum/attachments/img_4330-jpg.411428/

Shunts cannot be 0 ohms. They usually are a fraction of an ohm. Then the voltage drop across the shunt will determine the amount of current flowing. So on a shunt system, a volt meter is used and is calibrated to the current.
For example: A .01 ohm shunt will have a .01 volt drop across it when 1 amp is being drawn. 30 Amps will be .3 volts, etc. At 30 amps, the shunt will have to dissipate 9 Watts of heat that is wasted in the process.
Having said that, a calibrated piece of wire can function as a shunt. You will need an ohmeter that is capable of measuring fractional values. That is out of the realm of common digital multimeters out there. Just factoring out the test lead resistance in the measurement can be very complicated.
Craig

Wondering the value needed for this ammeter

I don't know about the LeBaron indicator? If it is an Ammeter using a shunt, the shunt may be inside the meter already. On the Charger meter, I believe the movement is magnetic. The needle indicates the current from sensing the magnetic field through the shunt strip.

no, its on engine bay. Is part of the engine harness wiring. Not just on Lebaron/Diplomats but in all Mopars. Just right to save the battery recharge process from the bulkhead and ammeter and just a thick wire is spliced from the alt side of the shunt to the cab to feed the undedash harness main splice

I dont know the actual ohms of them but the few I have had out of the harness were pretty long. I was told that the shunt carries about 9/10 of the load so if 10 amps are flowing 1 amp goes through the amp gauge and the shunt carries 9 amps. So the shunts ohms should depend on the amp gauge ohms to calculate the shunts ohms. And of course the longer the shunt the more resistance in the wire. They look like a normal wire to me but with a good bit of lenth to have the right resistance I assume. Ron

The only shunt wire I have had in hands, was barelly 3 or 4 inches, from a 75/76 Coronet

I actually pulled the harness apart on one and changed the lenth as I made it a little shorter so the gauge would show more as it never moved before. I would say it was 2 to 3 feet long. But I also worked at a Ford dealer for 8 years before I did 24 years at a Dodge dealer and it may have been a Ford as I dont remember which car it was but Ford also use a shunt type ammeter on some of its cars as it was an option. Ron

Determining the resistance of the shunt just requires measuring the current through it and voltage across it at the same time and using Ohm's Law. That's exactly what a regular ohmmeter does but the current is too low for the range of a normal meter and resistance of the shunt. With good instruments it's not that big of a deal.

I think you are describing the fusible link.

No, its the shunt... cars with shunts got in fact no less than 2 or 3 fuse links, instead the one pre 75 cars got

Here is an old wish I have had since learnt about this... check this thread I made LOOOONG time ago when I was learning about

http://www.dodgecharger.com/forum/index.php/topic,61947.0/all.html

71_deputy checked and got 0 ohms and looked like a regular wire

my new thread here is just confirming this reading from somebody else OR if there is somehow to know how to match a shunt with the ammeter... because I don't have any spec on the Diplomat/lebaron ammeter... don't even know if would be the same than any other Mopar ammeter with shunt system.

Hey Nacho,

I recently came across the ammeter sizing description on the Jamestown Dist website but I see you already are familiar with that.
That's a great picture in the FBBO thread. Interesting it has a capacitor. Do you have a picture of its circuit board connections.

Also interesting is that some ammeters do not have shunts. Probably cheaper although more limited.
http://www.triumphexp.com/phorum/read.php?17,1078873

For anyone more interested in how they work, the math and diagrams for shunt ammeters here:
http://www.tpub.com/neets/book3/7g.htm

Its possible that when Chrysler went to a external shunt meter, they weren't too concerned about the shunt resistance. They assumed it was in some range based on plain wire. The heavy resistor in-line with the meter movement was the key to it being approximately 60 amps at full scale.

Did you ever get a picture of the back of the 80 amp ammeter age?

I have more than 40 years experience measuring DC currents in mining including locomotive applications of more than 1000 amps. I have sized external shunts for the older style 0-1 milliamp meters so that the Full scale milliamp corresponds to whatever max amp the circuit needs, and also used various Hall Effect clamp on meters. I own Fluke direct measuring multimeters that go to 20 amps, and have the Fluke clamp on Hall Effect attachment that measures up to 400 amps at 1 millivolt per amp.

If someone will give me part number(s) for Chrysler meters that are typical for older cars and pickups i would be willing to stop by a local to me parts store with my meters and measure the shunt and how many milliamps it takes to move the meter full scale.

I would guess the shunt for an automotive gauge of either 0-60 or 0-80 full scale amps is a thin but noticeably wide bare metal bussbar set on spacers to allow heat dissapation.

https://www.amazon.com/DROK-Anti-Rust-El...nt+less+ammeter

I would be surprised if the guts of the meter movement is not the almost standard 0-1 milliamp.

When new and clean of corrosion at the screw connections I would guess that the shunt buss-bar surface temperature is less than 40 degrees F more than the air cooling it. Safety concerns would lead me to believe that Chrysler would desire a max shunt temperature of less than the flash point of gasoline vapor on a 115 degree Death Valley day during severe duty vehicle testing.

It is possible that Chrysler used a precise length of 6 gauge or heavier wire to provide the shunt resistance, as the ohms is usually way less than 1 ohm, and 0.01 ohms is not unusual.

Wouldn't the FSMs of those years have an ammeter test proceedure,
something like:
turn on the headlights when the engine is off and battery at 12.6 volts
and check that the ammeter reads 20 amps of draw?

An alternative amp gauge:

http://archive.siliconchip.com.au/cms/A_30551/article.html

A cheap digital ammeter for checking current on auto fused circuits that could be used to measure shunt resistance by connecting to the Fuse Buddy" male spades with female spade crimp on connectors.

https://www.amazon.com/305M-Fuse-Buddy-Mini-Tester/dp/B000W8FMXU

I was told the reason Mopar went to the shunt type amp gauge was because so many customers complained about the amp gauge going to discharge at an idle at night with the lights and maybe the heater on. And I do know that many of the shunt amp gauges in some Mopars never moved much. I remember my moms 74 Monaco wagon that had a shunt stye amp gauge and I know when I turned the headlites on with the car off I could not see that amp gauge move at all. Course on the non shunt type like the 60's Mopars used the amp gauge would go way over to discharge if you turned the lights on with the eng off. So it made me wonder if they went with to much on the shunt where it was carrying more then 90% of the load on some ? And most customers never knew as they just new the amp gauge did not go to discharge at idle at night. But I always felt the shunt style did not give the customer a very good watch of the charging system as I felt even if it stopped charging it wont be seen right away. Ron

Will go later with this