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09-03-2020, 06:45 PM | #1 |
Junior Member
Join Date: Sep 2014
Posts: 3
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Should there be voltage across the high beam and low beam terminal?
The headlights on my 1936 Ford pickup had been converted to sealed beam halogens. Wires coming out of the switch at the bottom of the steering column were dead ended. A headlight switch was mounted in the dash. Only the ground wire and the low beam wire were connected to the headlight. I connected the high beam wire and installed a floor mounted dimmer switch.
There are 12 volts when the ground lead is connected to the ground wire with the positive lead connected to the high beam (with the dimmer switch on high beam), and there are 12 volts when the positive lead is connected to low beam (with the dimmer switch on low beam). However, checking across the high beam terminal and the low beam terminal, there are 12 volts (when the dimmer switch is on high beam) and there are 3.6 volts across the high beam and low beam (when the dimmer switch is on low beam). Should there be voltage across the high beam and low beam? I am not sure if this is okay or if the headlights are not wired correctly. I appreciate your help. |
09-03-2020, 07:14 PM | #2 |
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Join Date: May 2010
Location: Star, MS
Posts: 4,025
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Re: Should there be voltage across the high beam and low beam terminal?
Sounds normal to me. The side that is not energized is providing a ground path for the volt meter through the bulb from the energized side.
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09-03-2020, 07:27 PM | #3 |
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Join Date: Nov 2012
Location: Wichita KS
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Re: Should there be voltage across the high beam and low beam terminal?
The voltage (current) goes through the filament in the bulb to ground and eventually back to the battery. So, there is current (and voltage potential) in the grounds and grounds tend to back feed through other connections. They may or may not be wired correctly, are they working ok?
Last edited by JSeery; 09-03-2020 at 08:19 PM. |
09-03-2020, 08:01 PM | #4 |
Junior Member
Join Date: Sep 2014
Posts: 3
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Re: Should there be voltage across the high beam and low beam terminal?
I appreciate the information.
I installed the headlights and both the high beam and low beam are working okay. Thanks again! |
09-03-2020, 08:35 PM | #5 |
Junior Member
Join Date: Sep 2014
Posts: 3
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Re: Should there be voltage across the high beam and low beam terminal?
Your answer makes perfect sense. I wasn't thinking of it in those terms.
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09-07-2020, 03:06 AM | #6 |
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Join Date: Sep 2016
Posts: 628
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Re: Should there be voltage across the high beam and low beam terminal?
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The fix was to change to Sylvania H6024 bulbs. They do NOT have a connection between high and low beams. |
09-07-2020, 03:25 AM | #7 |
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Join Date: May 2010
Location: East Shore of LAKE HOUSTON
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Re: Should there be voltage across the high beam and low beam terminal?
.
AND....ya gotta keep in mind that a volt meter does not NECESSARILY measure voltage. More realistically, it measures voltage DIFFERENTIAL between two points. You can have a thousand volts at a particular connection. But place BOTH meter probes on that SAME electrical point, and your meter will show 0.0v (zero volts)....DIFFERENTIAL. I'm just saying that one must remain fully-aware of exactly what it is that you are measuring. But what do I know? DD |
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