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What are the normal voltages going to the dynamo D and F

To: MG List <mgs@autox.team.net>
Subject: What are the normal voltages going to the dynamo D and F
From: "Pat Harris - \"sammler\"" <sammler@bellsouth.net>
Date: Tue, 02 Jan 2007 11:29:33 -0500
1962 MGA 1600 MKII

I would like to know what some of the "normal" voltage readings should 
be for a system in good operating condition.

I'm having charging circuit problems - the Ignition light remains 
illuminated as long as the switch is ON. 

I've read quite a bit of info about testing the dynamo and how difficult 
it is to accurately test the control box but I thought that there should 
be some "starting" point with "good" voltage readings.

Here is info I have but it is with the charging system which has failed. 
:-(  For all readings the engine is NOT running!

Control box       
        Ignition
OFF
Volts
        Ignition ON
Volts
E
        0
        0
D
        0
        7.82
F
        0
        7.82
A
        13.07
        12.49
A1
        13.07
        12.49


Voltage to coil 12.10

Voltage on yellow wire going to D terminal but NOT connected to dynamo - 
7.83 (therefore the wire is OK)

Voltage on yellow-green wire going to F terminal but NOT connected to 
dynamo - 7.82 (therefore the wire is OK)

readings with dynamo installed when failure was noted

    Voltage at dynamo D terminal (large terminal - yellow wire -
    Ignition ON) .35
    Voltage at dynamo F terminal (small terminal - yellow-green wire -
    Ignition ON) .35

        if dynamo is connected but NOT installed, therefore NOT
        grounded, the voltage on either terminal is 7.82


readings with another dynamo installed - from a parts car - installing 
it did NOT solve the problem

    Voltage at dynamo D terminal (large terminal - yellow wire -
    Ignition ON) .63
    Voltage at dynamo F terminal (small terminal - yellow-green wire -
    Ignition ON) .63

        if dynamo is connected but NOT installed, therefore NOT
        grounded, the voltage on either terminal is 7.86


If someone having a car with a good charging system has a chance to 
check the voltages I'd sure like to know your findings.

Fortunately replacements for the control box and dynamo should be here 
this week.  Planning ahead may have paid off as I ordered them the day 
before the system failed. :-)

Thank you and Happy New Year,
Pat




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