Is There a Voltage Regulator for the Radio Acc Power? - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 3 (permalink) Old 08-18-2013, 07:06 PM Thread Starter
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Is There a Voltage Regulator for the Radio Acc Power?

Ok guys, I am trying to hook up a voltmeter and have come across a weird issue. I had it hooked up temporarily directly to my amp wires through a switch and got reasonable readings, but today I tried hooking it up more permanently to the radio acc wire so it would come on with the car.

Here's my problem, with it hooked up through the amp wires (basically straight to the batt) I was getting readings of about 13v - 14.5v (verified with a DMM.) But when I have it hooked up to the acc radio wire I get a reading of 11.9v - 12.3v. I checked the batt with my DMM while it was reading 12v and the DMM said 12.9v, and when I turn off the car, I get ~11.5v on the gauge and 12.7 at the batt.

So my question is: is there a voltage regulator for the acc circuit? And is there something near the a pillar that is switched with the ign that is not regulated? I got the gauge to monitor my actual voltage of the car for when I upgrade my stereo at the end of the month and this really doesn't tell me much.

If all else fails I suppose I'll just use a relay to get the correct voltage while still coming on with the car.


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post #2 of 3 (permalink) Old 08-19-2013, 12:42 AM
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Sounds like normal voltage drop to me. The general rule is that you'd lose 0.1v per connection. Since your first reading was a near direct link to your battery, you'd read something very close to battery voltage. Your next reading was quite a ways further downstream, so the voltage will bleed out a little and you'd have a lower reading. Either that, or your have unwanted resistance somewhere. Corroded wires are a usual suspect. The voltage regulator is usually built into the alternator to keep it from overcharging the battery and causing damage. If you check the battery voltage with the car idling and read something like 16v+, that's most likely a voltage reg. problem. Hope that helped.

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post #3 of 3 (permalink) Old 08-19-2013, 01:22 AM Thread Starter
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Yeah that makes sense. I guess I'll be running a relay, as I really want to know what's really going on back there. Thanks.


2007 Cobalt Ls Manual Coupe
Kenwood Excelon X996, RF T3 Components, RF Power 6x9s, Sundown Audio SA10, RF Power T600.4, Alpine MRP-1000, Kinetic HC-1800, Black headlights, FX-R HID 55W, Custom led tail lights, Led reverse lights, Airbox mod.
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