Voltage drop on App voltmeter while driving.
 Public Forums   Started by 1974 golf 1500LS   2022-03-17 09:29:08 +01:00   Comments: 9    Viewed: 3916

  1. With a handheld voltmeter my battery is fully charged at 12.6volts, testing across the battery with the engine running at idle and revved up charging shows 13.9volts. charging light functions and going out on dash correctly. Belt is tight not slipping. 
    On the App voltmeter running at idle it shows 12.5volts but the faster the car is driven the lower it goes, down to 11volts at 60mph. turning on something like the radio will drop it 0.5volts. The charging light on the dash never comes on.  
    The charging system seems to check out fine, is the alternator failing under load?
    1974 golf 1500LS, 2022-03-17 09:29:08 +01:00
  2. Leen APK
    Leen APK Administrator Staff Member
    Hello,

    please measure the voltage directly on the red wire of the 123 ignition and the gnd (or when aplicable the blue wire). My guess would be there is a bad connection somewhere.

    Kind regards, Leen
    Leen APK, 2022-03-18 14:37:32 +01:00
  3. When is blue wire applicable?

    What voltage reading am I looking for and is this at idle? 

    1974 golf 1500LS, 2022-03-18 21:12:35 +01:00
  4. roman taylor
    roman taylor Member Ankara
    I am also getting the same error as you, can anyone help me?
    roman taylor, 2022-03-23 14:44:42 +01:00
  5. I have cleaned the battery terminals/ ground strap etc and renewed all the wire connectors for new ones and my battery charging voltage has gone from 12.9 to 13.4volts so that's better from the alternator.    I have now found that the red wire power from the coil to the distributor drops as the engine revs increase which is what i see at the 123 bluetooth dash volt meter, I have a ballast resistor with the coil and that seems to be dropping the voltage, as if I disconnect it and just bypass it with a test wire I see 12.5 or more constantly at the 123 voltmeter and it does not drop to 11, but i still dont see the 13.4v charging voltage from the alternator on the 123 dash volmeter.
    1974 golf 1500LS, 2022-03-23 16:55:07 +01:00
  6. Also, there are 6 posts on this thread. I can only read/see the first two, i have tried chrome/firefox/internet explorer on my laptop and chrome on my phone and all are  the same, it only shows me the first two posts, the only way I read a reply is in the email that a reply has been made.
    1974 golf 1500LS, 2022-03-23 17:09:29 +01:00
  7. I have a red coil from you, do I need the ballast resistor? (the car has run fine for 3 years with a ballast resistor fitted)
    1974 golf 1500LS, 2022-03-23 17:30:39 +01:00
  8. Leen APK
    Leen APK Administrator Staff Member

     
    Hi,

    The blue wire is applicable when present, not all of our distributors have this blue wire.

    The voltage our distributor measures is often not the exact same voltage as the output from the alternator. Often there are other power consumers on the same wiring, which causes a drop in voltage when turned on. This is completely normal and should not be any cause for concern. 
    So therefor, to check if the app displays the correct voltage, you will need to measure the voltage between the red and blue wire of the distributor and check if this corresponds to the voltage shown in the app, which can be different from the output of the alternator.


     
    The Bosch Red coil does not require a ballast resistor. We highly recommend NOT to use a ballast resistor, as this also gives you a changing voltage readout on the app.


     
    This should be fixed by now.
    Leen APK, 2022-03-28 08:58:41 +02:00
  9. Thanks, the forums now work again and I can view all replies. I will bypass the ballast resistor.
    1974 golf 1500LS, 2022-03-28 09:08:22 +02:00
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