Are Mopar shunts a simply wire or a known resistance wire ?
#2284931
04/09/17 06:21 PM
04/09/17 06:21 PM
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NachoRT74
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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/
Last edited by NachoRT74; 04/09/17 06:46 PM.
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2284990
04/09/17 08:24 PM
04/09/17 08:24 PM
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denfireguy
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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
2014 Ram 1500 Laramie, 73 Cuda Previous mopars: 62 Valiant, 65 Fury III, 68 Fury III, 72 Satellite, 74 Satellite, 89 Acclaim, 98 Caravan, 2003 Durango Only previous Non-Mopar: Schwinn Tornado
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2286186
04/12/17 01:18 AM
04/12/17 01:18 AM
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NachoRT74
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Wondering the value needed for this ammeter
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2286363
04/12/17 12:39 PM
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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
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2286896
04/13/17 09:48 AM
04/13/17 09:48 AM
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The only shunt wire I have had in hands, was barelly 3 or 4 inches, from a 75/76 Coronet
Last edited by NachoRT74; 04/13/17 09:49 AM.
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2287751
04/14/17 04:41 PM
04/14/17 04:41 PM
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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
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: denfireguy]
#2287998
04/15/17 12:57 AM
04/15/17 12:57 AM
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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
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.
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2288217
04/15/17 02:08 PM
04/15/17 02:08 PM
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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 think you are describing the fusible link.
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2288564
04/16/17 01:44 AM
04/16/17 01:44 AM
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NachoRT74
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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
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2288795
04/16/17 01:45 PM
04/16/17 01:45 PM
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NachoRT74
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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.html71_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.
Last edited by NachoRT74; 04/16/17 02:11 PM.
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2321544
06/15/17 10:53 AM
06/15/17 10:53 AM
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Mattax
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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.htmIts 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?
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2321842
06/15/17 10:33 PM
06/15/17 10:33 PM
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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+ammeterI 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?
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: NachoRT74]
#2321847
06/15/17 10:38 PM
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Re: Are Mopar shunts a simply wire or a known resistance wire ?
[Re: Mattax]
#2321955
06/16/17 01:31 AM
06/16/17 01:31 AM
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NachoRT74
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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.htmIts 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? Will go later with this
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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