QuestionQUESTION: i have been trying to install my head unit into my car and have got it working for a maximum of 3 seconds, it will then lose power and fade to off mode. I am just guessing but I believe the problem to be that the input power is supposed to be 13.8V and yet the car battery only supplies 12.4V what can i do to resolve the problem??
ANSWER: Hi Michael,
Your head unit should be able to work perfectly well on 12.4 volts. Just about all car audio equipment is designed to work with a voltage range anywhere from 11 to 15 volts. This is because the voltage level in your car, by design, will vary depending on whether the engine is running. A standard car battery, fully charged, maintains a voltage around 12.6 volts, but when the alternator is working, system voltage rises to above 14 volts. All car audio equipment is designed to work with the engine on or off.
It's difficult to say exactly what's causing your problem. A digital multimeter, even an inexpensive one, can be a tremendous help when troubleshooting a power problem. If I were looking for the source of the trouble, I'd start by measuring the voltage on the yellow wire and red wire in the head unit harness, using the black wire as the reference ground for my meter.
If the unit comes on for a few seconds as soon as you plug it in, but shuts down immediately and won't turn on again when you turn the key on, then you may not have any voltage on the red "accessory" power wire. The deck needs voltage on the yellow wire and the red wire before it will turn on, but many will cycle through a "reset" process when you first connect the yellow wire. That may be what you're seeing for three seconds. If you're not getting power on the red wire, the first thing to check is your vehicle's radio fuse.
I hope this helps. If you'd like to follow up with more detailed information on your problem, I'll see if I can help you troubleshoot. For example, does the deck turn on for a few seconds each time you turn the key on, or only when you first plug it in? What's the year and model of your car?
Brian
---------- FOLLOW-UP ----------
QUESTION: i checked the voltage from both wires using a multimeter, the memory wire(12.4V) and the Power wire (12.2V), as soon as wires are connected, time is available on the screen (from memory wire), however when i press the "on" button the player works for a few seconds then the power fades, my multimeters reads a voltage drop of approx 4V from both memory and power wires. The key is turned on through this process so i am getting power through both wires. I did try running the head unit while the car was running but the same thing hapened. My car is a Ford Laser 86 model i think
AnswerMichael,
It sounds to me that you may have a bad ground connection. This assumes that you used the deck's ground wire as the reference ground for your meter readings. It seems unlikely that there could be poor connections on both the red wire and the yellow wire, which would cause a 4v drop on each once the deck started drawing current. However, if there's a poor connection on the ground wire, it could cause a 4v drop, and you'd notice the effects on both the accessory wire and constant power wire measurements.
You can confirm this by repeating the voltage tests on the power wires, but use a known-good ground point for your black probe (clean chassis metal at the firewall or kick panel, or the outside ring of the cigarette lighter should work). If you don't see a voltage drop when you're using a known-good ground point, but you do see a drop when using the deck's ground wire for your meter's reference ground point, that would confirm that the deck's ground wire isn't in contact with a good ground source.
Many older Ford vehicles didn't use a chassis ground wire in the radio harness. They used a "floating ground" arrangement where the radio chassis was directly in contact with chassis metal. A black wire in a Ford radio harness often isn't a ground wire (in fact, some older Ford vehicles used a red wire for the radio ground). All this means that if you're using a wire in the Ford radio harness for your chassis ground connection, it might be the source of the problem.
I'd try connecting the new deck's ground wire directly to a clean metal point, behind the dash or at the firewall.
I hope some of this helps.
Brian
