my sister says her radio shuts off whenever she turns on the headlights... she turns the headlights on, after a few seconds the radio shuts off. it's an aftermarket CD-radio from clarion so i'm guessing it's shutting itself off when it lacks power. i plugged it in years ago with a wiring harnesses to match the ford plug, wrapped all my connects with lots of tape, and never had problems with it for years

i haven't seen her in a while but i'm thinking her alternator might be on the way out... it's a 96 escort. she got a new battery last winter. last thing i want is her to break down somewhere and have to shell out for an alternator and a new battery

i told her not to use the radio or anything else electrical until she has the alternator looked at

i heard a quick way of testing the alternator is to unplug the battery with the engine running... is this reliable? if my memory serves there's an electric guage in the dash... if the alternator was acting up how would you tell?

btw i've never changed an alternator. is it tricky? i remember by sonoma had a 4cylinder and changing the starter was a mess because of how things are mounted

 

Do you have a voltmeter to measure the voltage across the battery?? I think you might have some other wiring/electrical problem effecting the radio. If the alternator was not charging properly, then it should stop running before the radio stopped playing. It also would not start again without charging the
battery (or jump starting).

 

just so i understand... when the car is running does the car use power produced by the alternator or is it running off the battery while the alternator charges the battery

 

When your vehicle is running, then the alternator should be able to provide the current required for all the accessories, and to recharge the battery from the starting process. The battery's main role in life is to provide the many 100's of amps required to turn the engine over by the starter on the initial start. The battery also works as a "filter" to filter out the voltage spikes coming from the alternator. I hope this answered your question.....

 

yeah i'm always changing batteries in the middle of winter

but bear with me

if the alternator's not working then the engine should continue to function until the battery is run down? or won't start one day because the alternator hasn't been charging the battery?

i've been looking around on testing an alternator... from what i got i want to know how many volts and how many amps the alternator is producing... volts to recharge the battery and amps to power all the electrical utilities??? i also read something about voltage regulation to control the flow of power from the alternator to the battery???

i need a tutorial on this... when i understnad it i'll know the questions to ask

 

If you have a voltmeter, measure the voltage across the battery without the engine running. With a fully charged battery, you will measure 12.4V-12.6V. Start your engine and let it run at a fast idle for 2-3 minutes. Now, at
idle, measure the battery voltage again, and you should measure 13.6V-14.2V. After this, turn on all the accessories (headlights, heater blower, etc.), and you should still measure 13V or higher at idle. If the voltage is slightly less than 13V, increase the idle speed, and the voltage should increase. I hope this helps!!

 

Unpluging the battery while the engine is running is not a good way to test the alternator. Have her take the car to a local parts store like AUTOZONE etc. and they can test the alt and battery for free.

 

Sounds to me like someone hooked the ground wire to the illumination wire, it will have a ground while the headlight switch is off, but will be hot when on.

 

I am with pfogle on this. The radio is wired improperly. I have to dig in to my own wiring on my Ranger. It does something similar when the lights are on AND the wipers are on intermittant. The PO wired the radio in and messed it up badly. I looked into it once and shuddered because I didn't have the time at the moment to fix the mess. It is not hard or expensive to get an adaptor harness when an aftermarket radio is installed but instead people try to splice into the existing wires. My daugter had a similar problem on her Topaz and I fixed it. They had two power wires reversed on it and connections made with scotch tape... Mis-installed audio equipment is one of the big causes of automotive fires.

Get your alternator or charging system tested at a big parts store.

 

I swear I'm not trying to hi-jack the thread here, but a few weeks ago I had to change the starter solenoid on my truck. After I did that, my radio would not hold a preset station at all! I went over every wire twice, made sure nothing got crossed up and finally wired it to a constant hot source. It's a Jenson AM/FM cassette player so it's not high-tech, but I did have the memory lead wired to the old solenoid and hooked it up to the same post on the new. What happened?

 

BTW, I checked every fuse in and out of the radio and fuse panel and none were blown.

 

Big Hoss, sounds like the wire connector you were using had come loose. The radio requires a constant hot on the yellow wire to keep presets.

 

Yeah, I thought that too, but I checked every connector, fuse and wire and everything looked good to me. I even checked the internal fuse and it was a no-go.

 

i plugged the radio in years ago and never had any problem... i used a wiring harness and everything... i know the power leads aren't crossed because it's never had any trouble saving station presets

it's only started blacking out lately and now her battery light is going on

 

well the battery light going on is a sign that the alternator is crapping out. If it's bad, the car will be cranking slower than it used to, and soon, it won't start. It's really not hard to test an alternator. With the cheapest volt gauge in the world, just measure the battery voltage with the engine off. Keep measuring, and have someone start the engine. You should have more voltage with the engine running. Rev it up to about 2000 rpm, and you should have more voltage still. As long as you're seeing at least 13.5 volts with it running, it is fine. If not, time for a new one.

I'm thinking a wire connection in the wiring harness could be loose. Did you just twist them together? Or did you solder or crimp?