5 Answers
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The 7443 led bulb will function in either 7443 or 7440 sockets.
In the 7440 socket, the 7443 will have extra contacts that are not connected to anything.
The 7440 will not function in the dual bright dim mode in the 7443 socket.
The 7443 is a dual contact (d.c.) bulb. The dual contacts are connected to 2 separate circuits inside the bulb. One for bright or high beam (braking/turn signals) and one for dim or low beam (running/parking lights).
The 7440 is a single contact (s.c.) bulb. The 7443 led bulb can be used universally in either 7443 or 7440 applications.
so the 7743 will work in place of a 7740.
a 7740 will not work in place of the 7743
hope that helps
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7440 Bulb
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a 7443 will power full brightness in a 7440 socket.
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7443 Bulb
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Thanks for this explanation. When a 7443 is used in a 7440 socket, are some LEDs not active, or does the low power circuit use a different resistor (etc.) to change it brightness and (apparently) color ?