no power to head unit after alarm
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=122238
Printed Date: April 19, 2024 at 6:54 PM
Topic: no power to head unit after alarm
Posted By: elbartorex
Subject: no power to head unit after alarm
Date Posted: June 10, 2010 at 1:28 PM
I am running a clarion CZ200 HU in a 2000 Acura Integra. I hooked it up with a vehicle specific harness that I spliced to the clarion harness.
Unit functioned perfectly until I installed a Viper 5701 alarm. Now ACC power to stereo and cig lighter will not function. In cabin and underhood fuses are intact. Switched power on stereo harness probes 233mv as does each terminal of both the radio and lighter fuses.
Constant power to HU probes 12.4v.
Alarm functions perfectly.
Any ideas?
Replies:
Posted By: KPierson
Date Posted: June 10, 2010 at 5:49 PM
How did you test the fuse? If you just visually checked it there is a chance it is blown but still looks good. Chances are very good there is a fuse blown somewhere, you just have to find it!
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Kevin Pierson
Posted By: bloob
Date Posted: June 10, 2010 at 5:57 PM
could you just bypass the vehicle ACC wire and run a new one? might save a headache?
Posted By: i am an idiot
Date Posted: June 10, 2010 at 6:18 PM
Find the fuse that is blown. It will be labeled as radio or lighter.
Posted By: elbartorex
Date Posted: June 13, 2010 at 12:13 PM
neither the lighter or radio fuses are blown.
I tested the fuses visually and by probing the top contact points.
I also swapped the fuses with fresh ones to make sure they weren't partially blown.
Yes I could bypass the ACC to another source but that doesn't fix the problem.
Posted By: t&t tech
Date Posted: June 13, 2010 at 2:27 PM
I noticed you said each terminal of the fuses read 233mv! Which to me says it isn't the fuse, but something tells me it's still a fuse problem!
Also technically speaking, bypassing the acc with a fresh wire will "fix" the problem, It just doesn't resolve the current issue! ------------- COMMIT YOUR WAY TO JEHOVAH AND HE WILL ACT IN YOUR BEHALF.
PSALMS 37:5
Posted By: elbartorex
Date Posted: June 14, 2010 at 11:44 AM
t&t tech wrote:
I noticed you said each terminal of the fuses read 233mv! Which to me says it isn't the fuse, but something tells me it's still a fuse problem!
Also technically speaking, bypassing the acc with a fresh wire will "fix" the problem, It just doesn't resolve the current issue!
so what would be my next step be? I was assuming that there must be some sort of major resistance on those two lines, but I don't know enough about electronics to know how to check that.
Posted By: KPierson
Date Posted: June 14, 2010 at 12:44 PM
Did you unplug the ignition harness during the installation of the alarm? I wouldn't be looking for added resistance I would be looking for an open in the wiring. Either you unplugged something and didn't plug it back in right (ie backed the pins out of the harness) or you have blown a fuse. If you have checked the correct fuses with an ohm meter and they are 100% verified to be good I would start checking any harness that you may have unplugged.
Also, if the radio and cigarette lighter have seperate fuses and neither of them work then that points to a wiring problem before those two circuts branch off from each other. That is what got me thinking that a main ignition harness may have been unplugged to install the alarm and something didn't go back together correctly. ------------- Kevin Pierson
Posted By: elbartorex
Date Posted: June 14, 2010 at 12:54 PM
KPierson wrote:
Did you unplug the ignition harness during the installation of the alarm? I wouldn't be looking for added resistance I would be looking for an open in the wiring. Either you unplugged something and didn't plug it back in right (ie backed the pins out of the harness) or you have blown a fuse. If you have checked the correct fuses with an ohm meter and they are 100% verified to be good I would start checking any harness that you may have unplugged.
Also, if the radio and cigarette lighter have seperate fuses and neither of them work then that points to a wiring problem before those two circuts branch off from each other. That is what got me thinking that a main ignition harness may have been unplugged to install the alarm and something didn't go back together correctly.
I unplugged the ignition harness to wire in the ignition and starter intercept from the alarm, but it was plugged back in and all of the ignition and starter functions work fine. There are only 4 pins on the plug and I have checked them multiple times.
The radio and lighter have their own fuses, so it must be something with the wiring pre-fusebox.
What exactly is an 'open'? You mean an open wire?
Posted By: i am an idiot
Date Posted: June 14, 2010 at 1:48 PM
An open is an break in the circuit. When a fuse blows, that is now an open.
Posted By: elbartorex
Date Posted: June 14, 2010 at 3:38 PM
i am an idiot wrote:
An open is an break in the circuit. When a fuse blows, that is now an open.
so if the fuses aren't blown I should be looking for a cut wire?
Posted By: KPierson
Date Posted: June 14, 2010 at 5:00 PM
I would start at the ignition switch and probe the circuit with a volt meter. Most cars take constant power to the igniton switch and then power individual circuits from there. It sounds like your constant and igniton circuts are unaffected so I would concentrate on the accessory circuit which is a yellow wire at the switch. It's a long shot, but maybe the switch itself went bad at the exact time you were installing the alarm? Check the voltage at the switch and then at the harness and then at the fuse box. In most Hondas all of those places are somewhat easy to access. It may also help if you got a wiring diagram for the car and checked to see if any other circuits are on the same feed and not working. ------------- Kevin Pierson
Posted By: elbartorex
Date Posted: June 16, 2010 at 1:55 PM
KPierson wrote:
I would start at the ignition switch and probe the circuit with a volt meter. Most cars take constant power to the igniton switch and then power individual circuits from there. It sounds like your constant and igniton circuts are unaffected so I would concentrate on the accessory circuit which is a yellow wire at the switch. It's a long shot, but maybe the switch itself went bad at the exact time you were installing the alarm? Check the voltage at the switch and then at the harness and then at the fuse box. In most Hondas all of those places are somewhat easy to access. It may also help if you got a wiring diagram for the car and checked to see if any other circuits are on the same feed and not working.
if the ignition switch was bad, then the car wouldn't start, right?
Posted By: i am an idiot
Date Posted: June 16, 2010 at 2:28 PM
There are several switches inside your ignition switch. You could have a bad switch on the accessory section of the switch. The car will still start in this case.
Posted By: blanx218
Date Posted: June 17, 2010 at 8:26 PM
just to clarify the fuse thing. did you check for blown fuses in both fuse boxes? and did you check every fuse rather than just the ones labeled radio and cig lighter?
Posted By: soundnsecurity
Date Posted: June 18, 2010 at 11:13 AM
how did you connect the alarm wires to the ignition harness? t-tap solder? if you used a t-tap then you may have cut most of the wire inside the jacket causing a bad connection and added resistance to that wire. solder can do the same thing if it is a cold solder.
if you wand to test this just make a jumper out of some 14ga wire and jump t across your connection on the acc wire.
if you dont catch this problem soon it might melt your wire harness
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Posted By: jcs091570
Date Posted: June 19, 2010 at 3:03 AM
Just a thought... just by looking at a fuse you can generally tell if it is blown, but sometimes you can't. Try a new fuse in the necessary places and see what happens. I found out the hard way and wasted hours trying to figure a similar situation out..when it turns out the fuse was blown where I couldn't make it out with my own eyes. Can always use a volt meter and test it for continuity. Sounds like your radio and cig lighter are on the same switched 12v ignition circuit.
Posted By: i am an idiot
Date Posted: June 19, 2010 at 5:48 AM
Did you ever have any wires shoved into the radio or cig lighter fuse slot? This tends to spread out the contacts of the fuse holder. You may want to check for that.
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