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Chris
Chris, Shop Foreman
Category: Dodge
Satisfied Customers: 13565
Experience:  Dodge/Cummins and Chrysler Certified Master Tech
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Alternator is good when tested off truck but battery light

Customer Question

Alternator is good when tested off truck but battery light is on
JA: There are so many things that can cause battery issues. Some simple, some complicated. The mechanics have tons of experience in that area. Will the car start?
Customer: Yes but battery light is on
JA: Glad to hear that. How old is the battery?
Customer: Brand new
JA: Anything else I can tell the Dodge Mechanic before I connect you two?
Customer: 2014 ram 4500 diesel
JA: Got it. Let's get this figured out. I'm sending you to a secure page on JustAnswer so you can place the $5 fully refundable deposit now. While you're filling out that form, I'll tell the Dodge Mechanic about your situation and connect you two. You'll be on the road in no time.
Submitted: 1 year ago.
Category: Dodge
Expert:  Chris replied 1 year ago.
Hello, my name is ***** ***** I will be assisting you today. Have you had the charging system voltage checked while the truck is running? It should be around 13.8 to 14.2 at both batteries. If it is below or above that then the battery light will come on. Also, is the check engine light on also? Chris
Customer: replied 1 year ago.
Yes check engine is on. I'm told that the ecm tells the alternator to charge or not charge. I pulled alt off and sent it to the alt shop. They tested it and said there isn't a problem with alt
Expert:  Chris replied 1 year ago.
Ok, that is correct regarding the ECM. Could be a problem with the ECM or wiring issue. Do you have a 12 volt test light handy? Chris
Customer: replied 1 year ago.
Truck is at shop but yes I have one
Expert:  Chris replied 1 year ago.
Ok. What needs to be checked first besides the charging voltage at each battery is to see if there is battery voltage at the large alternator stud with the engine off. If there is, then we know that the circuit between the alternator and right battery is good. Then the next thing is to check and see what trouble code has turned on the check engine light.
Customer: replied 1 year ago.
Ok
Expert:  Chris replied 1 year ago.
See if you can do those things and then report back to me. You will need to rent or borrow a scan tool or ask your auto parts store to check the codes.Chris
Expert:  Chris replied 1 year ago.
By the way, if you want to talk with me about this on the phone, I can turn on the phone call feature. Let me know,Chris
Expert:  Chris replied 1 year ago.
Hello, just checking back to see how it is going
Chris
Customer: replied 1 year ago.
All is good. Had a bad diode pack in alt. Thanks for the help
Expert:  Chris replied 1 year ago.
Aha! Too bad the shop did not find that when they initially tested the alternator. Glad you got it fixed though! Chris
Expert:  Chris replied 1 year ago.
Hello, I was wondering if you would please take a minute to rate my service when you get a chance. Please remember, the website will not automatically credit me from your deposit or subscription without your Rating! Please, use the Rating System Box and Rate our Q&A session today or. If you need to ask more questions, please feel free to ask!Thank you! Chris