no power to hu

[newb 10+ year member]

I've had the same setup Im using now for about 2 years. I recently took the whole system out because I was thinking about selling my car. I changed my mind about selling my car and this weekend, I reinstalled everything back to how it originally was. The problem is, my **** HU wont power up. I've checked all fuses and connections and everything looks good, hooked the HU directly to the battery and still no power, I checked the HU with a DMM it read 12v with the red wire and around ~.5v with the yellow. I also checked the vehicles harness (acc and power) with the DMM and everything matches up with the voltage readings I got from my HU, I also checked the voltage reading directly from the battery and sure enough it also reads 12v. Could it be the yellow wire? Im not sure how many volts it's supposed to be. Everything was working perfectly before. I also connected both the yellow and red wire together to see if there were any power and there was none. Ground was also connected to the same place it originally was. Someone help.

How many volts should the HU be, not being connected to vehicles harness? I checked just now, and it read somewhere between .2 for the red and .5 for the yellow. The black wire coming from the DMM I had it hooked up to the ground of the HU, is this right?

Another note, I tried connecting another HU and it's giving me the same problem. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

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[silvercookie 5,000+ posts]

you have the red and yellow wires backwards i think

the yellow wire is supposed to be 12 volts and the red wire is supposed to be ~.5volts.

 

[kovemaster559 5,000+ posts]

check the fuse inside or outside the HU

 

[BEAVER.989 10+ year member]

as suggested, check the in-line fuse within the yellow wire.

 

[SethPhillips 5,000+ posts]

well with the headunit hooked up the right way ( wire harness for the car ) the yellow should read between 12 car off-13.5+ volts car running, the red should read 0v with the car off, and 12-13.5v with the car on.

now if that is so, all the fuses in the car are good.

now check the fuse that's on the back or in the wire harness for the headunit..

what kind of headunit is it?

 

[boomzilla 10+ year member]

my hu did the same, i had to hook my 12v constand and switched together to make mine work

 

[mil81 10+ year member]

Also, when you hooked the HU directly to the battery, did you have the yellow and red wires connected together, and touching the + terminal, and the black wire touching the - terminal?

 

[newb 10+ year member]

well with the headunit hooked up the right way ( wire harness for the car ) the yellow should read between 12 car off-13.5+ volts car running, the red should read 0v with the car off, and 12-13.5v with the car on.
now if that is so, all the fuses in the car are good.

now check the fuse that's on the back or in the wire harness for the headunit..

what kind of headunit is it?

The fuse in back of the HU is good. It is an Eclipse cd8445. I'll double check the voltage readings. Thanks.

 

[newb 10+ year member]

Also, when you hooked the HU directly to the battery, did you have the yellow and red wires connected together, and touching the + terminal, and the black wire touching the - terminal?

I had the red and yellow connected together and touching the + terminal, but I had the black wire grounded. Was it suppose to be touching the - terminal?

 

[SethPhillips 5,000+ posts]

The fuse in back of the HU is good. It is an Eclipse cd8445. I'll double check the voltage readings. Thanks.

check the fues with a multi meeter or test light sometimes fuses can be blown and look fine

I had the red and yellow connected together and touching the + terminal, but I had the black wire grounded. Was it suppose to be touching the - terminal?

yes.

 

[BEAVER.989 10+ year member]

I had the red and yellow connected together and touching the + terminal, but I had the black wire grounded. Was it suppose to be touching the - terminal?

It shouldn't matter whether you use the - terminal or a chassis ground, provided you have a good chassis ground.

 

[newb 10+ year member]

It looks like Im going to have to test it with a test light. Anybody know what voltage readings if any is the HU supposed to have not connected to the vehicle?

 

[NissanKicker 10+ year member]

use the battery to test it again.

... This time add the Remote wire to the Red & Yellow... touch the ground to the negative terminal...

( Remember, you do have to push the power button for it to turn on )

If it doesn't turn on then it's the H/U

 

[mil81 10+ year member]

It looks like Im going to have to test it with a test light. Anybody know what voltage readings if any is the HU supposed to have not connected to the vehicle?

Voltage is power. Nothing has voltage without a battery, or other power source. So your Head Unit won't show any voltage anywhere. The only power you can test is the voltage going to the HU. As stated above, you should have 12V constantly on the yellow wire, and 12V on the red wire when the key is turned on. That is tested by setting your Multi Meter to VDC, holding the black lead on a good grounding point (Black wire should work), and the red lead on the wire you wish to test. Test both of those, along with hooking the HU up to the battery again. As stated above, don't forget to push the power button to turn it on.

 

[newb 10+ year member]

Ok guys, I finally figured this dilemna out. The wire harness for my HU was bad. How I figured this out was, I hooked up both HU's directly to the battery, red and yellow to the + terminal and ground hooked up to - terminal. The CD8445 didnt power up, but my older Eclipse HU did. My first question to mind was, "****, maybe my 8445 is dead?" So I swapped harness's, and sure and behold, the 8445 powered right up. I didnt have the time to check why the harness from the 8445 was messed up, but Im assuming there could be a short or maybe as someone else stated earlier in this thread, the fuse could be bad even though it looks fine. Thanks for all your help guys. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif