battery light on

scrapper · Oct 2, 2016

I have found several problems and repaired them. The battery was load tested by a battery place and was good. I cleaned the battery terminals and had to replace the end of the positive cable. I found the starter wire end was broken in half, put new end on it. It the light is still on. The meter shows it is charging in normal range. It doesn't seem to want to start, very slow at turning over. It runs rough when it starts. I tested at the battery negative post between the cable and the post with a meter to see if it read any voltage, the way to check for a short. I did that with the key on and with it off. What else would cause the problem? What else should I check? :annoyed:

Dane.Vettor@outlook.com · Oct 3, 2016

hey you better check your alternator.may be the belt or alternator pulley bearing itself can cause this problem.

adsm08 · Oct 3, 2016

You do know the battery light doesn't mean there is a problem with the battery, right?

RonD · Oct 3, 2016

Battery should show 12.3-12.8volts engine off
Then it should show 13.5-14.8volts engine running

Battery Light in the dash Powers the alternator, yes, an alternator needs power to start working.
When you turn on the key battery sends 12volts thru ignition switch to the Battery Light bulb in the dash, other wire on the bulb is connected to the alternators Voltage Regulator(inside alternator), if alternator is not spinning(engine off) then it is a Ground(0 volts), so Battery Light Bulb Lights up, 12volts + Ground = light bulb on

When alternator is spinning(engine on) then it should be producing voltage so now Battery Light bulb has 12volts + 12volts which = light bulb off

If battery voltage shows 14+ volts at startup then battery light circuit has a short to ground on the Light Green wire that goes to alternator.
If battery voltage is below 13.4volts at start up then alternator is not working.

If you have replaced the ends on the Positive battery cable to starter motor, then do the same for negative cable, there is no 12volts if there is no 0volts.
The Ground cable carries the exact same amps as 12volt cable, that is how DC volts work, if starter motor needs 100amps to turn fast and positive cable can handle 200amps then all is well............on that cable, if Negative cable can only handle 75amps then that is all the amps that can pass to the starter motor.
Think of electricity as a 1 lane road, and amps is speed, you are going 100mph then come up to someone driving 75mph, no passing, so you can only go 75mph.
To get 100amps to starter motor BOTH + and - need to be able to pass at least 100amps

scrapper · Oct 4, 2016

Well I took truck to get it checked out it at the battery place, shut it off went inside would not start when I came back out. Push started it took it home and parked it. The battery had a full charge, battery light has been on for about 2 weeks but did not have any problems. I had already ordered a starter from ebay so didn't want to buy another one. I cant help wondering if the starter was causing problems? If the alternator was bad the battery would have died a long time ago. I will check the negative cable but I replaced it about 1 year ago.

RonD · Oct 4, 2016

So the "battery place" couldn't hook up a volt meter and test system after you push started it?

Bad alternator is not a high volt or no volt thing, alternator can drain battery and charge it or barely charge it.
Voltage regulator can cycle on and off so a battery can last a long time and then one day no starter motor.

If Battery light is on when engine is running then battery is being drained, or there is a short on the Light Green wire, on or in, the alternator.
This can quickly drain the battery or slowly drain the battery
Simple test is to turn on head lights and fan blower to high while engine is idling, you should hear alternator load engine a bit as voltage regulator cranks up the amps.
If engine starts to bog or miss then you are running in battery power only

scrapper · Oct 4, 2016

I was only wanting to make sure I got it home about a 20 min. drive. The guy did load test it and that was not the problem. I should have the starter on Friday then I will take it back for them to check. I cant help wondering if it was shorting out or something causing the light to come on? The starter was making some crackling noises like it was shorting out or something but off and on with the key turned. I do not know that much about electrical systems, if the alternator was bad it would have been dead a long time ago. I was hoping the starter was causing it but probably more wiring problems?

scrapper · Oct 4, 2016

I was told to pull the positive cable with the engine running. If the engine dies its a alternator problem. I was also told to check the battery voltage then start it and check what the voltage is by a guy at work. He said it did not matter if it passed the load test. I have to replace some stuff under the hood so I will take the alternator in and have it checked out. Thanks for the help Ron I had no idea there was that much involved in the battery charging system.

scrapper · Oct 6, 2016

I replaced the starter today and it fired up but am taking the intake apart to put gaskets and injectors in. Will take the alternator in on Saturday.

RonD · Oct 6, 2016

The "pull the battery cable while engine is running" will damage charging system in vehicles made after about 1985, it was used when you had External voltage regulators, so 30+ years ago.

There isn't that much to a charging system, you just need a volt meter to test it
And a volt meter used the correct way is way better than taking an alternator out to test it, once alternator is out of the vehicle you may as well rub it 3 times and say "abracadabra it's fixed"
Exactly the same as taking it to a parts store to test it

Haywire6000 · Oct 6, 2016

Do not do the pull a battery cable off test like Ron said, that's a could way to fry electronics, which happen to be what makes your truck run.

scrapper · Oct 6, 2016

Thanks for the info I did not know that.

battery light on

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