hello guys.my battery light just came on a couple days ago. so where do i start? the Pat just keeps going but i dont want to be stuck on the expressway anytime soon..can corrosion on the Terminals cause it the light to come on? looks like it has some on there :nerd:i hope its not the Alt ive already looked at a video on changing that thing never seen such a job for that ^_^
Battery light
chrisPatriot08
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hello guys.my battery light just came on a couple days ago. so where do i start? the Pat just keeps going but i dont want to be stuck on the expressway anytime soon..can corrosion on the Terminals cause it the light to come on? looks like it has some on there :nerd:i hope its not the Alt ive already looked at a video on changing that thing never seen such a job for that ^_^
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494 Posts
Yes, loose terminals can cause the battery light to come on, but so can lots of other things. Stop guessing and take the car to an auto electrician
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9 Posts
well terminals are tight. no corrosion now ,belt is tight guess its battery or alt ohh and wont start now(dead)
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4,653 Posts
A bad battery will not trigger the light
Light is triggered by fault in electrical current
99% of the time its the alternator failing
1 can get the battery and alternator load tested at most auto shops
Places like autozone will load test the battery for you
I would start there
Light is triggered by fault in electrical current
99% of the time its the alternator failing
1 can get the battery and alternator load tested at most auto shops
Places like autozone will load test the battery for you
I would start there
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1,597 Posts
Terasec, some web sites claim that a bad battery with a dead or shorted cell can cause the light to come on???
Corroded wires, i.e. a bad ground connection, can cause a light to come on.
Also, even though the OP says the terminal connections are tight, I have seen very slight (aka invisible) oxidation of connections be enough to cause a poor connection. The terminals and connectors should be cleaned, then tightened.
My point is to check, and recheck the easy things before assuming the alternator system is bad. I twice replaced alternators to no avail, then found a bad wire/connection that was the cause. Test equipment, even a simple multimeter can get one started diagnosing these problems.
OP, please follow up with your solution to help us all learn.
Corroded wires, i.e. a bad ground connection, can cause a light to come on.
Also, even though the OP says the terminal connections are tight, I have seen very slight (aka invisible) oxidation of connections be enough to cause a poor connection. The terminals and connectors should be cleaned, then tightened.
My point is to check, and recheck the easy things before assuming the alternator system is bad. I twice replaced alternators to no avail, then found a bad wire/connection that was the cause. Test equipment, even a simple multimeter can get one started diagnosing these problems.
OP, please follow up with your solution to help us all learn.
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some cars might have different things that triggers the light
generally its the voltage in the charging system to the battery that triggers the light
i can pull the battery on the pat run off the Alternator and not get the light
i have had low battery for different reasons and not triggered the light
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ok so im helping him with the patriot issues. we replaced the alternator and the lights still on, bench tested the old one and its good also the battery tested good. they said the alternator was putting out no voltage it died as soon as we got home. i checked the main power to the alt wire and it looks good. the two smaller wires appear good by sight as well. im going to put a multimeter on there tommorrow. my questions are how much voltage should the two small wires be putting out and where exactly do they go? is there a fuse/ or relay i can try or am i fighting a bad wire?
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battery and alt are good.still not charging and light still on
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I'm not good at electrical things and electrical diagnosis. I had a John Deer tractor at work with the same symptoms as yours. Alternator/battery tested good, but the system did not charge the battery. After lots of digging, I discovered a bad relay in the electrical circuit and remembered that earlier I had a broken light wire that shorted out and blew a fuse (maybe the relay cause???). $80 part from John Deere.....$30 part from a Subaru dealer!.....yes, I googled the OEM part number and discovered it is used on Subarus also.
When time permits, I will query my factory service manual and see if it offers diagnostic help.
EDIT: A quick peek at my service manual shows that the charging circuit is controlled by both the TIPM and PCM (power control module), with the PCM monitoring the charge circuits for the most part. The PCM "should" store a DTC (diagnostic trouble code) readable with an OBD code reader. That should "begin" to tell you where to look. But, the manual does say to check the easy things first: battery, alternator/decoupler pulley, fuses, belt, ground and other wires, before doing the OBD. And, it emphasizes that the OBD code(s) are a symptom, not necessarily the cause. It will not tell you which component of a circuit is bad.
I'm also going to continue preaching to you cheap azz guys to invest in a factory service manual. pre 2011 ones are available for download on ebay for $7 and newer models can be had from a Canadian source for about $90.....will pay for itself with one repair, and all the correct specs (torque, etc.) are at your finger tips.
And, to milspectees who says "Stop guessing and take the car to an auto electrician": if a person has a diy mentality, there is nothing wrong with spending some time to educate oneself on repair procedures in order to be more self reliant. There is a learning curve and sometimes "throwing parts" at a problem before proper diagnosis does cost some money. But, you learn from mistakes and in later years you can save significant $$ (sometimes not) by diying. I learned appliance repair just studying the internet and saved numerous dryers, refrigerators, and washers with simple <$50 dollar repairs. Calling a technician and spending $300 is not cost effective on today's throw away appliances. To each his own. Spend time, money, and/or both to get the results.
When time permits, I will query my factory service manual and see if it offers diagnostic help.
EDIT: A quick peek at my service manual shows that the charging circuit is controlled by both the TIPM and PCM (power control module), with the PCM monitoring the charge circuits for the most part. The PCM "should" store a DTC (diagnostic trouble code) readable with an OBD code reader. That should "begin" to tell you where to look. But, the manual does say to check the easy things first: battery, alternator/decoupler pulley, fuses, belt, ground and other wires, before doing the OBD. And, it emphasizes that the OBD code(s) are a symptom, not necessarily the cause. It will not tell you which component of a circuit is bad.
I'm also going to continue preaching to you cheap azz guys to invest in a factory service manual. pre 2011 ones are available for download on ebay for $7 and newer models can be had from a Canadian source for about $90.....will pay for itself with one repair, and all the correct specs (torque, etc.) are at your finger tips.
And, to milspectees who says "Stop guessing and take the car to an auto electrician": if a person has a diy mentality, there is nothing wrong with spending some time to educate oneself on repair procedures in order to be more self reliant. There is a learning curve and sometimes "throwing parts" at a problem before proper diagnosis does cost some money. But, you learn from mistakes and in later years you can save significant $$ (sometimes not) by diying. I learned appliance repair just studying the internet and saved numerous dryers, refrigerators, and washers with simple <$50 dollar repairs. Calling a technician and spending $300 is not cost effective on today's throw away appliances. To each his own. Spend time, money, and/or both to get the results.
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9 Posts
thanks for the info
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1,597 Posts
Do places like Autozone still do free OBD code reading? If so, I can then tell you what the code points to.
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my nephew is gonna look at it when he gets off work.. thats what he said he was gonna check
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