When I turned on my headlights on tonight, I noticed my horn was weaker. When I turned my headlights off, my horn was loud as strong as ever. What gives? Is this normal?
Bottom Line Up Front:
At engine idle speed yes that would be normal. For normal cruise speed -- I'm not sure.
For a "T" that does not have a starter / generator and is running a magneto powered horn and headlights and the engine is at idle that is very normal. At higher engine RPMs with a good magneto, you shouldn't notice it that much if at all.
The same is true for a "T" with the starter / generator when the engine is at idle. If you have a great battery, you won't notice it much. But at idle with a standard "T" generator, your lights and horn will drain more electricity than the generator is putting out. So they will be getting the additional energy from the battery. At higher engine RPMs the generator should be set to put out enough electricity (amps) so that both the horn & lights work fine.
Note that on my 1970 VW that is also generator equipped, the lights dim a little when I am at idle because the generator was not designed to produce a lot of energy at idle speed. I only notice they are dimmer at idle when I have the car parked next to the garage and when I speed up the engine to back up, the light pattern on the garage becomes brighter.
If it is also occurring at normal RPM for driving, with the lights on, then Iíll let someone who honks the horn and has the lights on at night answer that one.
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