| RAK402 | -- 04-06-2021 @ 10:03 PM |
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Assuming everything is in good shape (good ground, good switches/dimmer, good wiring) how much current should the headlights in a stock (6 volt, positive ground)/stock bulbs) 1940 Ford? I have dim headlights. Cycling the dimmer switch did not help, and I am about to start chasing connections and grounding issues. I have a 39 Standard, loop type ammeter installed in the car, it shows a current draw of between 15 and 20 amps when I turn the lights on (I am guessing it is not a terribly precise instrument). A new, old stock voltmeter is installed in the panel-battery voltage is solidly in the green. Thank you all in advance.
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| TomO | -- 04-07-2021 @ 9:36 AM |
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The best way to isolate your problem is to check the voltage drop from the battery to the headlight. The total drop should be about 0.3 volts, but up to 0.5 is acceptable. Connect a volt meter with the black lead (com) on the NEG terminal of the battery and then probe the connector for the headlight bulb with the red lead (+). Turn on the lights and read the meter. You can find the source of excessive resistance by moving the red probe to the next connection that is closer to the battery. Each bullet should give you 0.05v improvement and the switches should give you 0.1v improvement. Check the grounding circuit by connecting the red lead to the POS terminal of the battery and probing the grounding wire in the headlight bucket. The meter should read less than 0.1V. If it is higher, check your ground strap to the firewall. You can also run an extra grounding wire from the fender to the firewall to see if that is your problem. Tom
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| jims33 | -- 04-07-2021 @ 5:13 PM |
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If you know the wattage of the bulbs, double it and divide by the voltage you see at the battery and this will be the current (amps) that they should draw. Any extra resistance will reduce the current and make the bulbs dimer. Maybe take the tail light bulbs out to simplify things. Watts equals volts times amps.
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