OK, at 4 am I finally stopped for today after getting stuck on something that is either because it's 4am or because there is an actual issue. I'm in the middle of installing my system and I've been checking for a clean grounding voltage with each step to ensure I don't fubar something. Here is an example pic :


The problem is when I connect the wire harness for the head unit, the voltage reading starts going all over the place, though usually in the 100 V range. Here is an example pic :


Both readings were taken with the battery ground disconnected & with the meter on the positive battery terminal & on a common ground bolt that is not the one connected to the battery negative.

With the wiring on the head unit, I first tried using one of the side bolts that I saw someone else point out in another post, but the ground cable was too long (almost 24") on the harness provided. I cut that down to 6" & changed to using the matching wire on the wire harness instead, but this didn't change anything. All other wires are matched wire for wire with the exception of the main constant power that is connected back to the battery with a fused 10 awg line.

For the love of God, someone please help me here. I'm nearing the end of my vacation & my wife is thinking I simply wasted my time in 90-100 degree heat working on this thing half the week.

 

Is the multimeter on auto range? have you tried adjusting the range/scale??

If the only thing hooked up to the battery is the positive terminal and you are grounding the meter on the body of the car, you shouldn't get any reading at all..
Is the headunit connected to the harness??

 

That's 91 mV or 0.091 V - nowhere near 100V (or 13.8V for that matter.)

I didn't understand what/where/how you were measuring, but if the ignition is on, and you are reading 0.091V at your radio harness on the ACC and/or Battery line, there is probably a blown fuse for the radio in your fuseblock.

- Project

 

*nods*

yup, that's 91 mV. or .091 V. compared to your 12 V potential, that's like .76%, which might be in the realm of built in error.

if i'm understanding this correctly -- w/ the ground to the battery disconnected AND you're measuring to the car body - you have no circuit. 91 mV is probably just a background noise reading or something...

exactly.



this does sound like a 4 am error....

connect up the ground on the battery again, and check your numbers.

 

Do'h, I missed seeing the m in the mV due to the darkness & time. I'll throw it back on again then and give it another go. I just didn't want to connect it and have things go up in smoke.

 

don't worry, at 4 AM? we've all been there...

 

Forget 4 am, I went until almost 11 am today after starting around 6 pm last night. I got most everything installed that I planned to get done this week, but I am having another problem.

It seems like the remote turn on isn't working properly, so I probably have it connected to the wrong wire on the harness. My question now is should it be connected to the remote amp output off the headunit harness or should I be tapping the accessory wire? The headunit powers up fine, but the amplifiers don't always turn on. There isn't a short or any blown fuses (checked already).

 

You should use the HU output if possible. If you use ACC power then the amp will be running even when the HU is off.

Use your meter and check for +12v on the HU remote amp output when the HU is turned on, then follow the path to the amp and make sure you have +12v there too. If you do and the amp doesn't turn on, sounds like a bad amp. If you don't have +12v at the amp turn on terminal, there's either a wiring mistake or your amp requires more current than the HU can supply, which I think is unlikely.

You can always measure the current required by the amp turn-on by disconnecting the wire on the turn-on terminal and putting your meter (set to amps) between the +12v terminal and the turn-on terminal on the amp. The amp should turn on and the meter will read how much current it takes to do it, which should be in the milliamp range (<10 milliamps). Most HU can supply a couple hundred milliamps on the remote amp output.

I can't tell from the pictures (glare) but you may not have a meter that can measure current. Many of the pocket meters don't include a current range. Even my pocket Beckman "Industrial" meter doesn't have one.

.

 

be sure you've got the amp turn on lead tied into an amp turn on signal, and not just a power antenna signal.

some HU's only send a power antenna signal when the tuner is selected. check to see if you power up when you turn on the radio...

 

For some reason it just doesn't seem to like the remote amp lead off the headunit's wire harness, so I just tapped the accessory wire & that seems to work fine for my needs. I rarely (if ever) am in the car without music playing, so having the amp not power down when I turn the radio off is a non-issue.

Thanks everyone.