No 12v constant

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=78818
Printed Date: July 14, 2025 at 6:31 AM

Topic: No 12v constant

Posted By: genhawk
Subject: No 12v constant
Date Posted: June 06, 2006 at 8:44 PM

I don't seem to have a 12v constant in what remains of my factory harness. 12v ignition I do have, but not having radio memory is super annoying.

Can I just run one straight through from the positive battery terminal? If I did, it would need an in-line fuse correct? If so, what kind?

Thanks in advance!

Replies:

Posted By: dwarren
Date Posted: June 06, 2006 at 8:50 PM

There is no problem in running your own lead directly from the battery, so long as you properly fuse it.

The fuse holder style can vary, however I recommend a simple spade fuse holder, and the fuse size will be dependant upon the wire size.

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Posted By: Silvrefox
Date Posted: June 06, 2006 at 8:57 PM

What kinda car you drive? Maybe we can help...

Posted By: dwarren
Date Posted: June 06, 2006 at 9:13 PM

Have you checked the fuse for your factory lead? That may procure a constant again.

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Posted By: dwarren
Date Posted: June 06, 2006 at 9:15 PM

Silvrefox wrote:

What kinda car you drive? Maybe we can help...

Yes that info would be useful, and checking the fuse for the factory constant lead (fuse for the radio) should be your next step.

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Posted By: genhawk
Date Posted: June 06, 2006 at 11:43 PM

Thanks, it's an 84 Nissan pickup, I tested all the harness wires with a meter but no 12v constant. No idea why, it looks like all the wires are there. I did check the fuse, and it's good, but maybe I'll try swapping it out with another one just in case.

I really can't understand why there isn't one...but since I got everything else working, oh well...

Other than the regular fusebox one I don't believe there are any other inline fuses. Is there somewhere else I should look?

Thanks for the replies!

Posted By: oman76
Date Posted: June 07, 2006 at 12:40 AM

I don't think your Nissan was prewired with a 12V constant at the radio harness. The radios that came in those trucks had analog tuners vs. digital tuners. There was no need for the radio to have 12V constant. Best thing to do if you haven't yet is run a wire from the fuse box or the battery .

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Alpine 7903/Kove Aphex Signal Processor/
Streetwires/MTX Blue Thunder Pro 400X5/JL Audio XR570-CXi/Polk Audio DB Tweeters/Image Dynamics IDQ10D4 V.2

Posted By: genhawk
Date Posted: June 07, 2006 at 3:04 AM

OH! I guess that might explain why I couldn't find one, hehe.

I thought it was a user error, since I don't do this often.

Posted By: djfearny2
Date Posted: June 07, 2006 at 6:54 AM

In most Cars the constat fuse is in the engine. and the acc fuses are in the car.

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Jon
Installer/Help Technician
---coral springs florida---
mecp certification is not always needed. I have it and it has not helped me out at all. my experience out shines it.