stereo resets when horn pressed

I have a 2001 honda accord with a single din kenwood head unit powering infinity speakers all around and a single kicker sub in the rear. Now my issue is that whenever i honk my aftermarket hella horns, my iPhone that is plugged into the head unit gets reset and the music resumes a few seconds later. When i first put the horns in i did not have this problem but it has recently started doing this. i don't know what the problem seems to be as i have checked all grounds and there isn't any issues that i can see going on. Any ideas are appreciated, Thanks in advance

Is the iPhone powered of the same fuse or same sub circuit? Maybe a bad connection or insufficient wire gauge.

However since it started recently, it may indicate a weak battery - it has aged and doesn't have the same hold-up or "big capacitor" behavior that it should, or did.   And the alternator may not react fast enough to fill the dip caused by the horns.

It could also be a high voltage spike... Same thing - worn battery.


There are various fixes to the above depending on what the issue is. If the battery is "acceptable", then putting the iPhone on a separate circuit, or adding suppression didoes for the horns etc.
Note that many take feeds for audio & computer type stuff direct from the battery (via a fuse of course!) and not from existing circuits thru cig-sockets etc to help prevent such noise and dip issues.
The BIG-3 also relates.

The above should be tried before replacing the battery (unless you deem it a nice early warning that prevents you being stranded somewhere, but I suggest a voltmeter instead).
Adding a capacitor across the iPhone's supply may also help.

I thought it was the battery also so i had that replaced a few weeks ago. the iphone is plugged directly into the head unit via usb so i dont know how to add a capacitor for it. The only thing i have yet to try is the big 3, but i dont know if that will even fix this problem

Ah - I didn't think of the iPhone being directly powered by the HU. IMO a sag or spike is unlikely to travel thru the HU to the iPhone - ie, a 12V HU should have a reasonably filtered 5V output.

But, something is causing it...

So everything worked fine for (a long?) period. It then played up so you replaced the battery.
That worked fine for a while (a few weeks) and the problem returned?
If so, I'd suspect the battery. But that might be because of an alternator fault - ie, undercharging. (It should be ~14.0 - 14.2V under normal circumstances; no more than 14.4V long-term.) But that in turn could also be from bad connections etc.

I'd try to eliminate the above possibility, especially if the scenario occurred as I described. It could be a dud or poorer quality battery. But otherwise the problem could IMO be due to many factors, maybe even spike radiation.
Are the horn power cables well away from the other power (or audio) cables involved? The horn should be powered thru its own fuse and relay direct from the battery.

Ya everything was fine for about 5 months and then it started to do this. had the battery replaced because it was dying fast. but the problem did not go away after the battery was changed. the alternator seems to be pumping the right amount of juice when i tested it a few weeks ago. and i have checked my connections and all of them are solid hooked up to the relay that came with them. How are you able to fix spike radiation?

The only way to figure this out is with a volt meter. Do you have one or have access to one?

Ya i have a few i can use

Remove the radio from the dash and check the voltage on the Red and Yellow wires of the radio. Check voltage while blowing the horn to see which of the 2 wires shows a drop in voltage.

When testing, place the black meter lead to the chassis of the radio. If both voltages are dropping, place the black meter lead to a known good ground and try again. If the voltages are now staying steady, you have a bad ground for your radio. If only one voltage is dropping, let us know which is dropping.

I tested the above method and neither wire voltages dropped when the horn was pressed

You installed some sort of after market horn? What horn and how is it powered?

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I have hella supertones wired with the relay that came with the horns

OK. And how are they powered, and how are they grounded?

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They are powered from the battery and grounded to the chassis right next to the battery. And that contact point is sanded down

If listening to a CD or the Tuner, do those sources shut off like the Ipod/Iphone?

I just tried a CD and the radio and neither of them reset. its just my iphone that gets reset

ttrimm208 wrote:

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I just tried a CD and the radio and neither of them reset. its just my iphone that gets reset

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Then it's not likely being caused by a power issue, it's more likely either an iPhone cable issue or something defective in the 5V power supply inside the head unit. I suggest trying a different iPhone interface cable and see if you get lucky.

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When you checked the voltage on the yellow wire, did the voltage fluctuate any at all when you blew the horn? If so, how low did it drop?

Well i tried a different cable and that didn't work. And no the yellow wire stayed at a constant voltage. I'm gonna see if i still have warranty for it and try to get a new one in tomorrow