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skytoastar
New User
Jun 5, 2010, 3:13 PM
Post #1 of 2
(3662 views)
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Car horn doesn't work
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The car is a 2003 Chevy Cavalier sedan with about 75000 miles. Some time ago the car horn stopped working. Then the stereo stopped working (which is unrelated to this issue). We left on vacation and didn't drive the car for about a month. When we tried to start the car the battery was dead. We have a second car and we didn't need to drive the Cavalier so we just left it there until the semester was done. Now that I'm out of school I have time to work on the car. The stereo problem was solved and I don't think that problem drained the battery. The horn leaves me suspicious, however.
The first thing I checked for the horn was the fuse. It was good. Then I checked the relay. The relay works just fine making an open with 0 V applied and a short with 12 V applied. So then I check the voltages on the lines going to the relay. The lines that switch the relay are at a constant 10.2 V whether the horn is pressed or not. The lines that get connected by the relay also have a constant 10.2 V. If I take the fuse out, there is 0 V across both pairs of lines. The battery voltage was measured to be 12 V.
When I tested the relay, 10.2 V is more than enough the cause the relay to close the circuit. But 10.2 V seems like a weird voltage level. Could something else on the horn circuit burnt out and be acting like a load now? This thought makes me think it was the horn that drained my battery. I would have tried to do other things but I can't find the horn itself and the wiring past the relay connection is hairy.
Any thoughts?
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 5, 2010, 4:50 PM
Post #2 of 2
(3656 views)
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Re: Car horn doesn't work
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That's a 12v horn. If the battery voltage is 12v then there should be 12 reaching the relay. You need to find out where the voltage drop is. That 10v could drop even more when the horn is called for.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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