I have a 2020 ST with 54k miles and recently had to replace the battery for a second time. Shortly there after I received intermittent warnings about checking the 12v charging system. This persisted for about a week with no issues start up or other wise. It became a consistent warning that came up every time the car was driven so I had the alternator tested today and it failed. I am in the process of replacing the alternator but cannot seem to get the old one free. Does anyone have any insight on the best way to remove the alternator and/or access the bottom side and wiring connections on the rear?
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Need guidance on replacing the alternator.
- Thread starter MattC0509
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Thread Starter
#3
Thanks for the info and I did get it figured out. Unfortunately charging issues never went away. Got in down the street to a local Pep boys and the alternator was testing as bad only putting out 12.4v under load. Seemed odd that a brand new alternator could be bad right out of the box but nothing is impossibly so I was able to get another installed today. Immediate charging issues so I run forscan and am getting 12.49 volts at the battery. No way I had two alternators back to back be bad. Anyone have any thoughts on anything to check or look for? Nothing else has been disconnected during the alternator replacements. That said It was at a Ford dealer for 2 months having the transmission rebuilt and replacing the rear. Battery issues and subsequent charging issues occurred 4 days after picking it up from the dealer.
BMS itself could be the problem. I would unplug it's connector and see what voltage the alternator is putting out. You will get an error message when you do unplug it but this is just for testing purposes. Also, for the time being, change battery state of charge to 95% (from default 80)--it'll act more like traditional charging.
Thread Starter
#11
Good morning and thank you for getting back quickly on this yesterday. I disconnected the wiring to the BMS sensor at the negative terminal and had immediate start up with my battery light and charging system warning going away. Once hooked up and running Forscan I was getting 13.4v at idle to the battery. Is it safe to assume that sensor has gone bad? If it did go bad would it be all at once or is it possible it was causing the intermittent charging issues but they became constant? I have an appointment at a local shop today but obviously if I don't have to take it in I would prefer not to.
So if the alternator is putting out consistent voltages (no drops) with the BMS sensor detached, then something is up with the BMS. Problem is, I believe there are multiple factors that determine what voltages it will put out, only one of them being battery state of charge.
I would definitely try reconnecting the BMS sensor and then setting default battery state of charge to 95% in BdyCM. With that setting, you should get 14+ V with the car running when monitoring V Batt in Forscan.
Replacing the BMS sensor is easy enough but may not solve your problem...
https://parts.levittownfordparts.co...H62Y7VYZFbaeea_um8iRm9SWOTxVsshyARJ3wbQyEKTK2
Also, you using an OE alternator?
I would definitely try reconnecting the BMS sensor and then setting default battery state of charge to 95% in BdyCM. With that setting, you should get 14+ V with the car running when monitoring V Batt in Forscan.
Replacing the BMS sensor is easy enough but may not solve your problem...
https://parts.levittownfordparts.co...H62Y7VYZFbaeea_um8iRm9SWOTxVsshyARJ3wbQyEKTK2
Also, you using an OE alternator?
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Thread Starter
#13
So I was able to pick up a BMS sensor at local Ford dealer and I'm back down to 12.2v so that was not in fact bad. Also in my Forscan I do not seem to have the option to change battery state of charge. I'm not on an OE alternator at the moment as there were none available not just close by but largely any where in the US. That said for the original alternator to have been "bad" at 54k miles and then I purchased 2 different brand alternators that were also bad the odds are astronomically against that.
The original alternator may have been good. You can't go by what the voltage is because that is being controlled by the BMS.
While I did not have the same dash errors you did, I did have fluctuating voltages, dipping down below 12V at times. New battery did not help. BMS sensor replacement seemed to help temporarily. I did not replace the alternator because like you, I got rock stable 13.5-8V when the BMS sensor was disconnected. Only thing that helped was changing the Battery State of Charge setting from the default 80 to 95%.
I have all modules fully updated as well.
Not my pic but here is the setting in Forscan:
While I did not have the same dash errors you did, I did have fluctuating voltages, dipping down below 12V at times. New battery did not help. BMS sensor replacement seemed to help temporarily. I did not replace the alternator because like you, I got rock stable 13.5-8V when the BMS sensor was disconnected. Only thing that helped was changing the Battery State of Charge setting from the default 80 to 95%.
I have all modules fully updated as well.
Not my pic but here is the setting in Forscan:
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Thread Starter
#16
I'm thinking the original was/is good as well. I had to get the extended license for Forscan to update battery charge but unfortunately that made no difference. Still getting 12.2v. I've made an appointment with a local shop to try to sort it out for me tomorrow as I've bugged way too many people at this point to keep trying to get it done on my own. At this point there is a gremlin somewhere that's not the alternator, not the battery and not the bms.
Lastly double check your nuts on positive battery fuse panel are all tight. I remember someone reporting electric problems because one or more were loose after they replaced their battery
You definitely have head scratcher here...I hope you will update us on the results. I wouldn't be surprised if its
You definitely have head scratcher here...I hope you will update us on the results. I wouldn't be surprised if its
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Thread Starter
#18
Well first off thank you everyone for the support in this. Secondly the last little hail Mary that happened to be free was the answer. When I swapped the battery I only loosened the two nuts circled in yellow and obviously the one securing the the positive terminal. Well turns out the one circled in red was over 3 full turns loose even though I never disconnected it. Tightened it and immediately saw voltage under power in the mid 14s.
Thanks again everyone for being so quick to help me sort this. Forgot the picture!
Thanks again everyone for being so quick to help me sort this. Forgot the picture!
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