I'm going to assume your digital meter doesn't care which probe you place on the higher voltage location. If reversed the meter will just show negative.
Now I'm not quite sure what you did.
This what I thought you described.
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So I
assumed the battery voltage to ground was around 12.5 Volts.
And that's why I concluded there was resistance in the bulkhead connection.
Probably best to measure the battery voltage with the lights on.
Comparing voltages to ground is OK, but assumes the ground path is perfect.
Check the ground path by turning on the lights and measuring from the battery negative post to some body ground locations.
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Seperately - I meant to write this before. Not related to the bulkhead but is related to your initial question.
If you want to do a check of the ignition switch to see if its a major source of resistance, you can check the operation with the ohmeter.
-Disconnect the steering column connector.
- Measure on the switch half from the J1 (power in) to the Ignition, Accessory and Start terminals. Should be no connection.
- Turn key to Accessory. Measure from J1 to the other terminals. Q2 should have no resistance and the Ignition Run (Dark Blue) should be open.
- Turn key to Run. Measure from J1 to the other terminals. Q2 and Ignition Run (Dark Blue) should have no resistance. Start and Ignition (Brown) should be open.
- Turn key to Start. Measure from J1 to the other terminals. Q2 and Ignition Run (Dark Blue) should be open. Start and Ingiton Start (brown) should have no resistance.
When done, touch the meter probes together to see what the 'zero' resistance reading is. It might be 0 or it might be .1 ohms
If any of the connections showed above the baseline zero of the meter, there may be resistance of consequence in the switch.
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