Charging System Light

[James909]

Today when I was driving home the charging system light on the dash came on for about a minute and then went off. The car starts and runs fine and I didn't notice any problems while the light was on. I wish I would have checked the voltmeter while the light was on but the light was only on for about a minute and I didn't think to check. When I got home I checked the battery connections and they were tight. I also did a charging system check with the following results:
Car off-12.5v
Battery load test, with car off-12v
Car running-14.5v
Car running with electrical load-14v
Everything involving the charging system seems OK to me so I'm wondering is there anything else I should check? Why would the light come on and then go off? Also the battery is about a year and a half old. Even though the car seems fine now I just want to avoid any future problems. Thanks for everyone's help.
-James

 

[JohnJ]

Check that the belt is in good condition and the tensioner works properly. Also, try wiggling the little wire at the alternator with the engine running to see if it makes the light flicker.

 

[James909]

Thanks for the response. When I was checking the voltage yesterday I inspected everything and the belt was tight and in good shape. I didn't try wiggling the connection on the alternator though. I will give that a try later on today. Also I know that the battery cables on first gens were prone to corrosion. I believe my cables are original, could that cause the light to come on?

 

[jjstanza]

Did you drive through water? If some water splashed up on the belt it could slip a little until the water disapated, especially if you have the wipers and lights on (or any electrical load).

 

[Dannyboy]

I've had this same issue with my truck in the past and it cleared up with no issues. I also had to have a mechanic find a short in my signal wire.



The Battery light typically has nothing to due with your battery or the condition of it. It has to do with the alternator output. The light turns on if your alternator is not charging.

The alternator kicks on when your truck is running from a signal from the ignition, it actually makes the connection inside of your dash parallel to the "battery" indicator light (I just had this issue because I removed my factory dash, I needed to tie the green/pink stripe wire to a power source).

If your alternator is not spinning (like mentioned water making belt slip, belt tensioner loose, belt off track or alternator not making connections internally) then the function of the alternator is not creating the charge and will trigger light. If the signal wire from the ignition is interrupted this is the other reason that it may not kick on.

If you just saw this light for a minute I wouldn't sweat it, especially with the tests that you have completed your charging system is doing it correct. If you see it again, I would run a jumper wire with a probe (with the engine running) from your starter solenoid or battery into the green/pink stripe wire on your alternator while having a meter hooked up to your battery. You will instantly see it jump from the 12 range to the 14 volt range and the dash light should turn off at that point.

You can repair the shorted green/pink wire by hooking it up to any source of power that is supplied from power when the ignition is on. You do not want to hook it directly to the battery because it will drain your battery.

Confused yet? I am, but if I would have learned what I taught myself this past weekend about alternators the last time my truck was giving me issues I would have saved a hundred bucks taking it to the mechanic. Hope that helps someone.

 

[James909]

Thanks for everyone's help. Regarding the question about driving through water, no I didn't drive through any water any time near when the light came on. Dannyboy I will try those suggestions if the light comes on again. I think I understand what you're saying. But I drove to school and back today and the light never came on. Since when I tested it the charging system seemed to be OK and the light was only on for a minute I think I am just not going to worry about it unless it happens again.

 

[James909]

Update: Yesterday I was using the Ex to move trailers around my yard when the light came back on and stayed on. I also noticed that the dash voltmeter was reading low although I didn't know how low because it only says normal . So I used a voltmeter to check the voltage and sure enough it read 12.3V with the engine idling. The alternator had stopped charging. So I replaced the alternator today and the light is off and the voltage is 14.6V at idle. So I guess when the light came on before maybe it was because the alternator had stopped charging for a minute. I don't know how old this alternator was (probably stock) so I think the brushes were just worn out. Well all is well now, so I just wanted to post this in case someone else has a similar problem.

 

[91exploreron37]

Glad to hear you got it fixed before it killed your battery