Dissection and Study of a Mopar Ammeter

Electrical & Ignition

  1. MoparGuy68

    MoparGuy68 Well-Known Member

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    With all these current threads about the infamous Mopar Ammeter, and the fact that my Charger's charging system isn't working, I decided to take a CLOSE, in person, look at one of these little devices. The device with the villainous reputation as being a "ticking time bomb" just waiting to destroy your car's electrical system. Seems this little gauge is the focus of lots of controversy these days.

    This dissection is not of the ammeter in my Super Bee, but one from an extra standard Rallye instrument cluster that came with my car when I bought it. The cluster was filthy dirty! I thoroughly wiped it down and cleaned it off before I started taking photos. Odometer reads 32727.7 miles (from the looks of the cluster before I cleaned it, that probably is 132,727.7 miles).

    So let us see the condition of this little ticking time bomb, inside this cluster..

    Well, after removing the plastic bezel and unscrewing the ammeter, I must say it looked pretty damn good to me! The top half of the orange needle is a little faded, but other than that, it looked surprisingly good. The terminal post studs on the back of the gauge are solid, with no play or movement whatsoever. I don't see any evidence of burn marks or overheating.. A little bit of surface rust on the underside of the securing nuts, and on the little black strip, that goes between them and the back of the cluster.

    Needle seems to sit straight up and down, vertically. But it is shifted to the left of the white center mark, which is wider in width than the needle.

    Maybe this particular ammeter has taken a licking and kept on ticking? Or maybe the car it was in didn't have any nasty electrical issues to cause excessive current to travel through it.. I think we could say this is a survivor ammeter! And it looks like it would work without issue in a car with a solid electrical system.

    So damn hot today, 111 F, that it was more enjoyable to play with this ammeter in the cool house, then work on the car in the hot garage. Maybe I should do some of those resistance tests on this gauge like others were posting on here.

    IMG_3464.jpg IMG_3465.jpg IMG_3458.jpg IMG_3459.jpg IMG_3462.jpg IMG_3460.jpg IMG_3461.jpg IMG_3466.jpg IMG_3468.jpg IMG_3457.jpg
     
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    • MoparGuy68

      MoparGuy68 Well-Known Member

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      Here are some photos of the cluster it came out of, after I cleaned it up. I think this was the first time I saw a vintage Mopar odometer from, the inside, in person. Interesting to see the 6 wheels and the gears, etc.

      IMG_3446.jpg IMG_3447.jpg IMG_3449.jpg IMG_3452.jpg IMG_3451.jpg IMG_3455.jpg
       
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      • GrabberOrange69

        GrabberOrange69 FBBO Gold Member FBBO Gold Member

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        Ammeter gauge looks rather simple for something that can burn the car down.
         
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        • Dibbons

          Dibbons Well-Known Member

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          Let me throw out this question. My '65 A Body still has the points-style voltage regulator while my '72 B Body has the solid state electronic style. Who knows what year Chrysler made the switch on the new models?
           
          Last edited: Aug 2, 2020 at 12:12 AM
        • 72RoadrunnerGTX

          72RoadrunnerGTX FBBO Gold Member FBBO Gold Member

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          1970
           
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          • 72RoadrunnerGTX

            72RoadrunnerGTX FBBO Gold Member FBBO Gold Member

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            Careful where you store that thing, I’ve heard they will spontaneously combust for no reason at any time.
             
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            • rumblefish360

              rumblefish360 Well-Known Member

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              They beat up from loose connections and not having a fusible link. I hear from people all the time how I goona burn up my car but get no response when I ask who they know personally that had there car actually burn down from a failed device.
               
            • Nacho-RT74

              Nacho-RT74 Well-Known Member

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              :rofl:

              Not initially. From factory they are tight! The first problem on them is the lack of power coming from stock alts and the wrong sourcing to added accesories by the owners/"techs" from the batt/starter relay stud ( this happens because ppl doesn't understand how it works and what it means the ammeter reading ). This make for sure the ammeter get more stress than the needed.

              Ammeter is by default a low rate resistor but still a resistor, so any load going through will become into a small ammount of heat. If you keep constantly ( and unnecessarily) working the ammeter under constant and high loads, the heat gets increased.

              Studs are attached by pressure into the brass shunt. As any metal piece ( even more brass and copper ) the shunt gets stretched with heat and studs loose their installed pressure. This increases even more the resistance to the load, increasing exponentially the heat, getting more loose anything around untill get broken the isolation, and it happens what it happens.

              20170915_203806-jpg.jpg

              On this pic the isolation got cracked mostly sure because the nut got stuck and trying to get it loosen made to bend the shunt breaking the isolation, however whe can see how the overheat causes its damage on brass.

              Solution:
              -source correctly the accesories
              -upgrade the alt accordingly.


              And you are done

              ( also get upgraded the wire paths, but we are talking in this case just about the ammeter itself )
               
              Last edited: Aug 2, 2020 at 5:41 PM
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              • Nacho-RT74

                Nacho-RT74 Well-Known Member

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                It can be readjusted if you care. The needle is simply "overlayed" against the magnetic counterweight on back which is the piece what moves by the magnetic field variation going throught the brass shunt.

                The current path can get better just adding lead between studs and brass shunt. And of course being sure about upgrades and accesories this last is the most important.

                Adding lead ( soldering ) is also a way to fix it when is already loosen keeping the stock stud in use.

                Making the propper fix and upgrades the heat won't be a problem anymore to get worried about the lead geting melted.

                IMG_1084.JPG

                ( just a bit of lead is enough )
                 
                Last edited: Aug 2, 2020 at 5:45 AM
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                • kiwigtx

                  kiwigtx International Mod Staff Member FBBO Gold Member

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                  ...I see what you did there. :rofl:

                  Just a small segue here....I used a similar sized temperature gauge in place of an oil pressure gauge for my A100. They are effectively the same gauge, just different face plates. The operation is the same no matter which one you use....in case anyone gets stuck for one of the other. :)
                   
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                  • Nacho-RT74

                    Nacho-RT74 Well-Known Member

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                    Another failure comes from tighten up ( or overtight ) the nut studs on the wrong way. This is what comes from that.

                    img-20120306-01048.jpg

                    The first nut against the housing must be just barelly tight to keep the ammeter in place.

                    The second nut which hold the wires in place must be really tight BUT holding the first one with a wrench to keep safe from spin and get loosen the studs inside
                     
                    Last edited: Aug 2, 2020 at 7:56 AM
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                    • Nacho-RT74

                      Nacho-RT74 Well-Known Member

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                      NOTE: no one of these pics are my credit, but found on the web. This is a topic which has been largely discussed along the years and lot of ppl is agreed on this procedure to keep the stock system still in use and safer.

                      Myself already fixed a 70 Charger ammeter like this way before find this info on the web
                       
                      Last edited: Aug 2, 2020 at 8:08 AM
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                      • Hemirunner

                        Hemirunner Well-Known Member

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                        Probably not a huge risk with a stock factory electrical system. Now add in 50 years of corrosion, neglect and idiots cutting and splicing and adding in high current electronics, it could be a problem. I guess the ammeter becomes the fusible link in the end....
                         
                      • Nacho-RT74

                        Nacho-RT74 Well-Known Member

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                        And

                        462.jpg
                         
                      • rumblefish360

                        rumblefish360 Well-Known Member

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                        Yes, over taxing a 50 YO system is always a problem.
                        My car older cars do not see anything more than a stereo upgrade and maybe a MSD.

                        The fusible link should burn out first before the amp meter gauge. This is the hazard & fire protection link. You amp meter should have tight nuts attaching the wires on tight well mounted studs as shown above. Having less than this IS an issue just like anything else in, on, under the car.

                        No one here would run a car around with a worn out front end, loose connecting rod bolts, a seriously slipping transmission but they will trust old brittle non inspected wiring. Everyone will just trouble shoot the failed blinker or brake light when it fails. When your amp gauge fails, it’s ether a non running car or a fire.

                        So, everyone inspects everything on there car right?
                         
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                        • Nacho-RT74

                          Nacho-RT74 Well-Known Member

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                          our cars can run with more electrical equipments, but making the propper adjustments and correct upgrades, without get worried about the ammeter itself really, more than check its conditions.

                          is like consider the torque converter when changing the camshaft, or shocks with new T Bars.
                           
                        • rumblefish360

                          rumblefish360 Well-Known Member

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                          Absolutely! Running a higher amperage Alt. Is fine as long as the battery isn’t needing a hefty charge. A 40 amp gauge can be replaced with a 60 amp gauge. If you need more, there are ways to limit the amperage the gauges will see.
                           
                        • myk r sanchez

                          myk r sanchez FBBO Gold Member FBBO Gold Member

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                          50? Hell, wiring can go south long before the 50 year mark. It might be just GM's choice of materials in the 90's, but my 90's F bodys have brittle, disintegrating wiring issues and they're barely 20 years old, and these cars are cared for. Then again, no one's supposed to be keeping their cars for longer than four or five years anyway. I'm pretty sure the engineers or whoever builds any car sits and there and says, "hmmmm....what can we do to make sure this vehicle lasts 50 years and not cause any issues for anyone?"
                           
                        • dadsbee

                          dadsbee FBBO Gold Member FBBO Gold Member

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                          1978 (I was 16) I dash fired our '69 Fury II, not at the amp meter, but shortly in beyond the bulkhead. We got it out AFTER the fire started coming up through the defrost vent and by dumping sand/gravel off the side of the road in the vent, while the owner of the house I was in front of ran out and unhooked my battery. Voltage regulator stuck (and had been on and off for a while) and I forgot to turn the headlights on. My eyes rarely leave the amp gauge in any old car, you see it peg 40 and you turn on the headlights and that generally corrects things. If not shut the bugger off.

                          Looks like amp meter is the next oil thread here.. :)
                           
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