No alternator output at idle?

Are you SURE the engine isn’t shutting off because that’s exactly what will happen. Also note that late model Fords with battery management system (BMS) don’t charge all the time. Sounds like your device on/off settings need adjusted.

Hey guys. First post.

I picked up this 2020 ST last Saturday and am loving it so far. 31k miles on the odometer and all stock currently besides a K&N panel filter and Livernois tune.

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Speaking of the tuner however, this brings me to my reason for the post. After the vehicle has been warmed up and driven for a bit, when coming to a stop and idling, I've noticed the display on the tuner (Which is suction cupped to the windshield) will power off as if you turned off the vehicle, then turn back on when you begin accelerating again. If I manually re-activate the display and check the battery voltage reading, I'm seeing that it's fallen completely back to battery voltage (12.3-12.4) and then resumes proper charging voltage once the vehicle is in motion again.

Before I begin any further diagnostics on the vehicle and potentially open a trouble ticket with Livernois, I wanted to check if this is some sort of feature these vehicles come equipped with (The only thing I can reasonably think of is that the alternator possibly has some sort of electronic clutch that disengages for short periods at idle? I know manufacturers are getting very creative nowadays in regards to fuel consumption)? Perhaps this could also be something related to the OBD port voltage? I contacted Livernois to see what they thought and they stated I was the first person to report this behavior.

I have never had trouble starting the vehicle, no stumbling or hesitation at idle and I have never received any error messages for the charging system. The dealership I bought it from did install a brand new AGM battery just before I bought it.

Also worth noting that I had the auto start/stop tuned out.

How many RPMs is it idling at?

1000% positive the engine is staying running. The charging shuts off as if the auto start/stop were still enabled but the engine remains running. This doesn't seem to happen until the vehicle is driven for a bit and fully comes up to operating temperature.

It’s NORMAL for the BMS to interrupt charging. If there was a vehicle problem it will let you know. Check your device settings. You may need to turn it on/off manually.

Do you have another source of voltage reading like your radar detector? Also, you running the original battery? For a MY2020, I would think you'd need a new one. I think the Livernois is meant to display all the time so what you are experiencing is a little odd. I also think it's odd that it would be battery voltage at a stop and then full charging when moving. Usually if the battery is not target (80%) it will be full charging, even when idling--that is something like 13.9-14.3V for me, and will reduce as it gets closer to being charged. Some accessories will power off if voltage is too low. To me, sounds like something is going on with your car that is unrelated to the Livernois.

I do not have a tuner suctioned cup to my windshield with the ZFG E50 tune. Why is it even necessary?

FireDemon, was your fix still holding. I have been noticing lately my voltages fluctuating wildly... going as low as 11.9V. I suspect my BMS is failing. When I unplug it voltages are in 13.8-14.4V range. At least I know my alternator is good. Will probably replace the BMS next...

Nope. Still the same thing. And in fact, just the other night I came out of the hardware store and started the vehicle up to a nice "SERVICE CHARGING SYSTEM SOON" message.

I've owned it going on 2.5 months now and it's been the only indication that something may be wrong.

Nope. Still the same thing. And in fact, just the other night I came out of the hardware store and started the vehicle up to a nice "SERVICE CHARGING SYSTEM SOON" message.

I've owned it going on 2.5 months now and it's been the only indication that something may be wrong.