Pnormandin

I have checked my Acc and constant power into the radio and they both register +12v. The ground coming from the car is ok too. When I hook up the 2 power leads to the radio and then test the volatage again,without the ground hooked on the radio, still fine. ONce I connect the ground from the car to the radio, it cuts the constant power down to 3-4v and the acc power to 12v?
I have gotten the radio to work fine on the bench and the fuse in the back is perfect as well.

Can someone point me in a diagnostic direction plz?

thanks

rs_cindi

aftermarket radio or stock replacement? I installed a sony indash cd/radio and did not bother to connect the ground, as long as the antenna is plugged into the back of the radio it will work fine, been over a year for me and no problems at all.

NEEDAZ

Christ thats terrible. To tell someone that the antenna id a good ground. There isn't a worse ground in the car to use. What are you using for you ground reference when your making these measurements. The chassis ground or the ground in the harness. If your using the ground in the harness just ground the radio to a big piece of chassis. Find some good metal behind the dash. If you already using the chassis as your meter ground then there is a bad connection on the B+ wire. But it sound like you just need a good ground so go to the chassis. DON'T US$E THE ANTENNA AS YOUR GROUND.

rs_cindi

just curiious as to why the antenna is such a terrible ground. I hve had my Sony indash cd installed for over a year now and have experienced no electrical problems with the car. The antenna lead has to be plugged in anyway and in my application works perfectly. I will admit that I have never used a multimeter(don't own one, have no idea how to use one) to check voltages but then again I never had a problem. My car came without a radio and the previous owner had cut of the radio harness connector. I got a Mitchell on-line print out of the wiring, hooked it all up by my little ol' self and I have had no problems at all. Not to be a jerk about it but what am I risking by using the antenna for ground?

onesickss

iTrader: (1)

the antenna is a bad ground for a few reasons. When making a ground in a DC system the least amount of resistance in ground..the better. you are better off grounding the radio as close to the power source as possible. also since the antenna is mounted to the fender the current will have to travel through the antenna (which is carrying a signal which can emit noise through your system) but then it has to travel through all the panels, and welds and everything else. all you need to do is ground it to a nice soild piece of metal around the area where your unit is. HTH

NEEDAZ

Not being a jerk at all, I should have gone further(and maybe spell checked too) but it was late. Read till the end and you'll see how bad grounds can not only create noise, but can also cause damage to equipment.
First why resistance in the power wires (ground AND B+) is bad. Do you know ohms law? It states E=IR (or Voltage = Current x Resistance). So any time there is a resistance with current flow though it there is a voltage drop developed across that resistance. This is called voltage drop. The more current flow there is the more voltage drop there is. So any resistance in the power supply wires has the potential to have some voltage drop. I say potential because there is NO voltage drop until there is current flow. Now any voltage that is 'dropped' along the power supply wire (ground or B+) is voltage that isn't getting to what ever those power wires are connected to (like your HU). In a 12V electrical system it doesn't take much of a voltage drop to make a big difference. Your head unit has a 10A fuse in it. At 10A it only takes 0.12 ohms to drop 1.2V which is 10% of the supply voltage (1.2=10x0.12). Because the current flow to your HU changes all the time, this voltage drop change, and that creates transients. This is like having an AC signal riding right along the DC power that is making into you HU. If these get bad enough it can cause problems with sound quality. Looking at just that you may say that the B+ and ground are equally important. But it gets more complicated when you add things onto the system like amps, CD changers, and what not. They pass the audio from one device to the other by sending a signal with varying a voltage level. This level needs a zero reference and in car stereo land this reference point is ground. So ground is zero and MUST stay zero. If ground is bouncing up and down this zero is bouncing up and down. Now that signal is in reference to a moving point. It's like trying to add two numbers with one of the numbers changing all the time. This is THE MOST common cause of audible noise in the system (ignition noise and alternator noise).
So resistance in the ground path can cause 3 main problems.
1. Voltage drop so the equipment doesn't have as much voltage to work with.
2. Transients which can cause sound quality problem (but in all honesty most of the time this isn't an audible problem, unless you also have a ground loop).
3. Ground loops which can and do cause noise.
Now why the antenna is a bad choose for a ground. The ant ground is connected to the fender through the outside conductor of the coax. The point on the fender is often rusted or oxidized, depending if your talking about the steel fender or copper in the coax cable. The outside conductor of the coax is a relatively small gage wire, so it's fine as a shield for the RF because there is almost no current flow. Your head unit can pull up to 10A before the fuse blows. As the current goes up, so does any voltage drop, not only on the shield but also at that connection to the fender and the weld connecting the fender to the chassis.
How can any of this damage your HU. Well more and more manufactures are using a star grounding PCB architecture. This is a little much to get into now, but it means that the RCA ground (the outside conductor on the RCA plug) is no long connected right to the chassis. It is connected to a common ground point back by the harness. Travels from there through some small traces on the PCB and maybe some feedthroughs. It is a separate ground that is meant only for a vary small current. Most are now even adding a small suffuse mount fuse connecting the RCA ground to this common ground point. This fuse is NOT consumer replaceable. It is solder right to the PCB. If you have a bad ground at the HU or the amp connected to the RCA plugs the two units are can be a two different ground potentials. Say the amps power ground is bad. The amps power ground is essentially connect to the RCA ground inside the amplifier. So if it can't get a good power ground at power terminals it will try to ground itself through the RCA cable back up to the HU, through these small fuses and PCB trace to the ground on the HU's harness. The amp pulls a LOT more current then any of these parts where designed to handle (that's why the have the fuse there). So if you have a HU with the fuse it will blow, if you have a HU with out the fuse, something else will blow, usually the traces on the PCB. The other thing that isn't as common is if the amp IC IN the HU shorts, which they do, and the HU is ground through the antenna cable it can burn up the antenna cable before the 10A fuse in the back of the radio can blow.
You CAN'T over do the ground. rs_cindi, pull that HU back out and ground the HU to the chassis someplace. Just because things are working doesn't mean its right. I don't what to see anyone here have one of these problems.

And that the easy vertion. Any questions? If you're new to all of this, it may seem toughf to get head around. But it will become clear as mud.

rs_cindi

I appreciate the explanation, and the spell check. First and foremost, in my first post the point I tried to make is that if there was a grounding problem during install of just a head unit that the HU should work using just the antenna ground if all the other wiring is correct. I just made it too brief, I wasn't suggesting he run forever with the antenna ground, just use it as a fairly reliable test ground on just a normal powered head unit. The antenna has to be hooked up anyway for the radio to work when checking the installation. If there is a ground problem with the HU chassis ground it would most likely be at the point it attaches to the car, not the HU itself. If for some reason the metal being used for a ground is rusty/painted or otherwise not a good ground where it joins the rest of the car then you wouldn't have a proper ground. Bottom line is if the unit does not work at all with the antenna ground then there most probably is another problem. We have all seen the damage done when someone re-wires to install their high dollar sound system and then just basically guts the wiring to remove the stereo when selling the car. For what it is worth I am a huge believer in proper grounding ever since I experienced the mayhem caused by a broken ground strap from the block to the frame on my '73 Firebird. I guess with all the exhaust noise, body rattling and suspension squeeks I have when driving I just don't notice any stereo problems using the antenna ground.

teamcamaro

if you are losing voltage when u have a solid ground to the chassis, check the chassis to see if you hav current running through it. i spent about 2 weeks straight searching for a noise problem. i feel your pain because its so tedious. the best things to do to eliminate all problems is to run ur hot line straight from the battery and scratch the chassis clean before connecting the ground. that will ensure a clean +/-.

also, if your getting current running through ur chassis u hav a short. thats a bitch.