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1975 450SL
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I am having ignitions problems trying to track down. What should the ballast have in voltage with the key on I ask because older American cars drop the voltage not certain these work the same way.. I have 12.7 on both sides of both resistors. I check the resistance and it is jumping all over. If these were bad would they take out the ignition control. Thanks
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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I am having ignitions problems trying to track down. What should the ballast have in voltage with the key on I ask because older American cars drop the voltage not certain these work the same way.. I have 12.7 on both sides of both resistors. I check the resistance and it is jumping all over. If these were bad would they take out the ignition control. Thanks
I don't think you will get any voltage drop across resistors unless a current is flowing (points closed). With key on, there will always be battery voltage at the first resistor (0.4ohm blue). Not so sure about 0.6ohm (silver) because itis after the switchgear (transistor).

To test resistors, you need to disconnect one side and measure resistance with key off. They should be 0.6 and 0.4 ohms.

The system is described in the engine shop manual section 07.5 with test procedures in 07.5-520. Best to read all of that first.
 
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