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Old 10-03-2010, 06:48 AM   #1
emooheo
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Default 12v constant wire

my 12v constant from battery to connect my radio is missing for some reason, and I need to run a new wire. I have connected one straight from the positive terminal to the stereo but that doesnt seem too safe. It seems like to do it correctly it should go through the fuse box or something. Can anyone tell me how to properly do this?
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Old 10-03-2010, 07:34 AM   #2
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Default Re: 12v constant wire

its safe as long as you fuse the wire close to the battery or whatever ur gettin 12v from
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Old 10-03-2010, 08:08 AM   #3
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Default Re: 12v constant wire

Ditto the above^^^, a fused 12ga, [fuse as close to batt. as possible] or, depending on MM&Y of car you can just plug the HUs 12V+ constant, [yellow] into the 12V+ constan free pin on the under dash fuse box, it should be a 20A circuit, more then enough for the HUs 12V+ constant.
I use the fused 12ga to the batt. 94
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Last edited by fcm; 10-03-2010 at 08:08 AM. Reason: typo
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Old 10-03-2010, 10:43 PM   #4
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Default Re: 12v constant wire

thansk for the input. i ended up using an unused port in the interior fuse box.
http://causeforalarm.thecarthing.com...c/fuse_box.gif the red one on the left. It worked for a bit then i shorted it out and blew the fuse for it. What fuse controls that?
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Old 10-03-2010, 11:22 PM   #5
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Default Re: 12v constant wire

I'm confused... You blew the fuse, but you need to know where the fuse is? If you can't find the fuse, are you 100% sure that the fuse is blown? Have you confirmed that there is in fact, no power to that empty terminal? I only ask bc an aftermarket radio shouldn't pull enough current to pop whatever fuse controls that, if the info that FCM posted is correct. Is there anything else in your car that isn't working now that your radio stopped working? The other posts on your thread from Thabadguy, and FCM are safe ways to power your radio. At this point, if your radio actually caused whatever fuse controls that circuit to pop, I wouldn't advise you to power your radio from another circuit in your car, for risk of blowing that circuit's protection as well. I would just go straight to the battery, and put a 10 amp fuse at the wire as close as possible to the + terminal.
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Old 10-04-2010, 05:43 AM   #6
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Default Re: 12v constant wire

What is the make and model of your HU, or what is the size of the fuse that is either in the yellow line or plugged into the back of the HU, [by the power plug]?
Also, is the fuse in the yellow line or the back of the HU the correct fuse, it should not be bigger then 10A at most? 94
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Old 10-04-2010, 12:08 PM   #7
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Default Re: 12v constant wire

In mine its the yellow wire.
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Old 10-04-2010, 04:03 PM   #8
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Default Re: 12v constant wire

well, i heard a pop and there is no power going to the spot, verified by my voltmeter. It blew because i had an exposed wire and it shorted out.

after this happened i made sure there were no exposed wires and found an empty spot in the fuse box that had no fuse in it, nor controlled anything, but had 12v to it when the car was off/no keys in ignition. I then got a wire and wrapped it around a 10amp fuse and plugged it in.

radio works fine but I still would like to find the fuse that popped from before.
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Old 10-05-2010, 03:43 AM   #9
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Default Re: 12v constant wire

I'm having the same problem with my 1989 sedan all my wires are good but my constant 12v+ I looked it up and its the blue and white wire I don't know what the problem is as well I checked all fuses and none are blown....
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Old 10-05-2010, 05:58 AM   #10
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Default Re: 12v constant wire

Quote:
Originally Posted by projected3 View Post
I'm having the same problem with my 1989 sedan all my wires are good but my constant 12v+ I looked it up and its the blue and white wire I don't know what the problem is as well I checked all fuses and none are blown....
Should be a 7.5A in the engine bay fuse box, it is also the ECU fuse on a lot of Honda/Acura.

If you are installing an aftermarket HU in your 89, do not use the blue/white in the radio harness, it can not supply the current that aftermarket "high power" HUs need, either connect the HUs 12V+ constant, [yellow] to the fuse box free pin or run a fused 12ga from the batt. to behind the HU and connect the yellow to it. 94
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Old 10-05-2010, 06:10 PM   #11
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Default Re: 12v constant wire

Quote:
Originally Posted by fcm View Post
Should be a 7.5A in the engine bay fuse box, it is also the ECU fuse on a lot of Honda/Acura.

If you are installing an aftermarket HU in your 89, do not use the blue/white in the radio harness, it can not supply the current that aftermarket "high power" HUs need, either connect the HUs 12V+ constant, [yellow] to the fuse box free pin or run a fused 12ga from the batt. to behind the HU and connect the yellow to it. 94
Wich one is the free pin in the fuse box and how do I connect a wire to it thanks... So whats the white and blue wire for if not constant 12v+ ?
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Old 10-06-2010, 05:53 AM   #12
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Default Re: 12v constant wire

The white/blue in the radio harness is for the radio preset memory of the stock HU, it can not supply the current needed for aftermarket HUs to work properly, [RMS output].

On aftermarket HUs the internal 4ch "high power" amp is powered by the HUs 12V+ constant, [yellow] just like an off-board amp would have a 12V+ constant power lead directly from the batt., unlike a stock HU that the acc., [switched power] is used for powering the "low power" internal amp and the rest of the unit, the 12V+ constant, [white/blue] is just for memory.

You will notice a stock HU will still work even if there is no 12V+ constant, it will just lose memory every time it is turned off.
An aftermarket will not work without the 12V+ constant, it will also lose memory if the 12V+ constant is "turned off". 94
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12v, 2001, 2006, amp, battery, civic, constant, fuse, honda, huse, protector, radio, run, therminal, troubleshoot, wire

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