From: Snag_one@msn.com   
      
   On 5/11/2023 9:49 PM, 😎 Mighty Wannabe ✅ wrote:   
   > On 5/11/2023 8:47 PM, Snag wrote:   
   >> On 5/10/2023 7:33 PM, 😎 Mighty Wannabe ✅ wrote:   
   >>> On 5/10/2023 9:39 AM, 😎 Mighty Wannabe ✅ wrote:   
   >>>> On 5/10/2023 12:55 AM, Xeno wrote:   
   >>>>> On 10/5/2023 3:05 am, 😎 Mighty Wannabe ✅ wrote:   
   >>>>>> On 5/9/2023 10:39 AM, Xeno wrote:   
   >>>>>>> On 9/5/2023 11:34 pm, 😎 Mighty Wannabe ✅ wrote:   
   >>>>>>>> On 5/8/2023 11:58 PM, Ivan Vegvary wrote:   
   >>>>>>>>> 1948 Pontiac, 12V battery, one wire alternator (was working   
   >>>>>>>>> when parked 12 years ago).   
   >>>>>>>>> No amperage reading even at 2000 rpm.  Battery voltage 12.6V.   
   >>>>>>>>> Battery voltage with car running 13.8V, however amp meter only   
   >>>>>>>>> reads 0 or negative with headlights on. Placed an after market   
   >>>>>>>>> ammeter between the alternator and the battery.  Same reading   
   >>>>>>>>> as ammeter in the dash.   
   >>>>>>>>> How could this be?  Alternator supplies voltage but no current.   
   >>>>>>>>> After idle for 12 years maybe residual magnetism is gone. Needs   
   >>>>>>>>> to be excited.  Can't find a YouTube that shows me which   
   >>>>>>>>> terminals to zap.   
   >>>>>>>>> All help is appreciated.  I can certainly buy a new unit, but   
   >>>>>>>>> possibly have other problems.   
   >>>>>>>>>   
   >>>>>>>>> Thank you   
   >>>>>>>>   
   >>>>>>>> If you get 13.8V when the car is running, that means the   
   >>>>>>>> alternator is providing output.   
   >>>>>>>>   
   >>>>>>>> The alternator output is AC. You need to use AC ammeter to   
   >>>>>>>> measure the AC current output from the alternator.   
   >>>>>>>>   
   >>>>>>> Correction, the alternator output is DC. The 6 internal power   
   >>>>>>> diodes provide the necessary rectification. The 3 exciter diodes   
   >>>>>>> are meant to excite the field coils and set the generation   
   >>>>>>> process into gear.   
   >>>>>>>   
   >>>>>>   
   >>>>>>   
   >>>>>> Are you sure that's true for 1948 Pontiac?   
   >>>>>>   
   >>>>>> Maybe that alternator had been modified to use external rectifiers   
   >>>>>> and regulator.   
   >>>>>>   
   >>>>> Then it wouldn't be a single wire alternator, would it? Think about   
   >>>>> that for a moment. Alternators are, typically, 3 phase. That means   
   >>>>> 3 +ve power diodes, 3 -ve power diodes and 3 exciter diodes. If   
   >>>>> there is only one output wire, then all *rectification* and control   
   >>>>> has to be on-board.   
   >>>>>   
   >>>>   
   >>>> If the alternator really has DC output, then the car's [DC] ammeter   
   >>>> and external [DC] ammeter should register DC current.   
   >>>>   
   >>>> I believe somehow the alternator burnt the internal diodes, and the   
   >>>> owner rewired it as single phase [AC] output and used external   
   >>>> [bridge rectifier] after the car's dashboard [DC] ammeter. That   
   >>>> means the dashboard [DC] ammeter has not been working properly ever   
   >>>> since [because it was AC coming from the alternator]. A germanium   
   >>>> [bridge rectifier] was used so some reverse current is flowing back   
   >>>> into the alternator when the engine is not running but the key is on   
   >>>> auxiliary. That's when and why the dashboard ammeter registers   
   >>>> negative.   
   >>>>   
   >>>   
   >>>   
   >>> I've some made minor corrections in square brackets [    ] above to   
   >>> clarify my points.   
   >>>   
   >>> I think I have the correct line of thinking.   
   >>>   
   >>>   
   >>   
   >>   It must be quite difficult to blow smoke up somebody's ass with your   
   >> head so far up your own .   
   >   
   >   
   > Do you have a better explanation for a DC ammeter not registering any   
   > amperage at the alternator other than the alternator is outputting AC?   
   >   
   > The OP should try using AC ammeter to confirm that the alternator had   
   > been rewired to output AC, and external germanium bridge rectifier is used.   
   >   
   >   
   >   
      
      The simplest explanation is that the slip ring brush isn't making the   
   circuit to excite the rotor windings . That alone would explain the   
   voltage reading 12.8V while running - and slightly higher when stopped   
   and there is no current draw for stuff like ignition and instruments .   
      The next simplest would be that the internal regulator is bad , also   
   resulting in a lack of charging .   
   --   
   Snag   
   "You can lead a dummy to facts   
   but you can't make him think."   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)