help - voltage oscillates - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Last Lemming Alive · 07-02-2018, 06:33 PM

I flashed back from V4 back to V3 yesterday and noticed today that my voltage is oscillating form 12v to 14v - up and down and wont hold steady at 14V. is this normal? Even if I rev it it doesn't jump to 14v, it just continues to oscillate back and forth.

thoughts?

NCtoBRZ · 07-02-2018, 07:03 PM

Are you saying that it continuously oscillates? If so, that doesn’t sound normal. The voltage does fluctuate between 12-14 volts at different times though... but not a constant fluctuation.

Last Lemming Alive · 07-02-2018, 07:13 PM

Quote:

Originally Posted by NCtoBRZ

Are you saying that it continuously oscillates? If so, that doesn’t sound normal. The voltage does fluctuate between 12-14 volts at different times though... but not a constant fluctuation.

If I start the car and let it idle it stays around 14v, however, if I rev the car the voltage will drop to 12V and hold for a while. The AC is on as well btw and its 100 degrees outside.

Ultramaroon · 07-02-2018, 07:23 PM

Do you have a MIL?

Last Lemming Alive · 07-02-2018, 07:42 PM

Quote:

Originally Posted by Ultramaroon

Do you have a MIL?

there is no warning light that comes on.

I just took it on another drive. I noticed that if I rev the car the volts drop to 12V. If I come to a stop the volts go back up to 14V. I checked the voltage at the battery with a multimeter and it follows what's on the dash gage.

Ultramaroon · 07-02-2018, 08:09 PM

Quote:

Originally Posted by Last Lemming Alive

there is no warning light that comes on.

I just took it on another drive. I noticed that if I rev the car the volts drop to 12V. If I come to a stop the volts go back up to 14V. I checked the voltage at the battery with a multimeter and it follows what's on the dash gage.

Sounds like it's fine but the service manuals are in my sig line if you want to verify.

Last Lemming Alive · 07-02-2018, 09:05 PM

I would have thought that revving the engine would have caused the voltage to peak not drop.

Ultramaroon · 07-02-2018, 09:20 PM

Guess not.

Last Lemming Alive · 07-02-2018, 09:31 PM

I tried looking at the service manual however it’s not very clear what is normal and not normal. It talks about what the battery voltage should be but not necessarily what the correct charging amps and voltage should be at any specific rpm Or how to test it without having hook up a computer to it For diagnosis.

Semiihcircle · 07-02-2018, 09:57 PM

My BRZ does that too, im not too sure why. i cant even tell you when it happens, there is no set of particular conditions that occur when my voltage oscillates. but is not a constantly going from 12 to 14v and back to 12V. sometimes its just hanging out at 12V then jumps to 14V for a little while. there is no noticeable difference in ride.

I just accept it as is, at this point. im also completely stock for now!

Last Lemming Alive · 07-02-2018, 10:41 PM

Quote:

Originally Posted by Semiihcircle

My BRZ does that too, im not too sure why. i cant even tell you when it happens, there is no set of particular conditions that occur when my voltage oscillates. but is not a constantly going from 12 to 14v and back to 12V. sometimes its just hanging out at 12V then jumps to 14V for a little while. there is no noticeable difference in ride.

I just accept it as is, at this point. im also completely stock for now!

And how long has it been this way

Grady · 07-03-2018, 08:35 AM

Quote:

Originally Posted by Last Lemming Alive

And how long has it been this way

Mine is a new 2017, been that way since new. It appears to be programmed into the charge logic. Keep from overcharging the battery, reduce load on engine, or something?

Last Lemming Alive · 07-03-2018, 09:15 AM

Quote:

Originally Posted by Grady

Mine is a new 2017, been that way since new. It appears to be programmed into the charge logic. Keep from overcharging the battery, reduce load on engine, or something?

I have a 2017 too, but mine just started doing this after a year of ownership

Also I noticed mine drops all the way down to 12.0V unless I’m decelerating. Only under deceleration does it go up to 14V

PhyrraM · 07-03-2018, 10:48 AM

Perfectly normal for the 2017+.

Turn on the headlights, it will stay at a steady high voltage.

07-02-2018, 06:33 PM	#1
Last Lemming Alive Member Join Date: Feb 2017 Drives: WRB 2017 BRZ Limited w/ PP Location: Louisiana Posts: 97 Thanks: 2 Thanked 49 Times in 19 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	help - voltage oscillates I flashed back from V4 back to V3 yesterday and noticed today that my voltage is oscillating form 12v to 14v - up and down and wont hold steady at 14V. is this normal? Even if I rev it it doesn't jump to 14v, it just continues to oscillate back and forth. thoughts?

07-02-2018, 07:23 PM	#4
Ultramaroon chicken tonight Join Date: Sep 2014 Drives: a 13 e8h frs Location: vantucky, wa Posts: 31,914 Thanks: 52,239 Thanked 36,573 Times in 18,956 Posts Mentioned: 1108 Post(s) Tagged: 9 Thread(s)	Do you have a MIL? __________________ service manuals

07-02-2018, 09:20 PM	#8
Ultramaroon chicken tonight Join Date: Sep 2014 Drives: a 13 e8h frs Location: vantucky, wa Posts: 31,914 Thanks: 52,239 Thanked 36,573 Times in 18,956 Posts Mentioned: 1108 Post(s) Tagged: 9 Thread(s)	Guess not. __________________ service manuals

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07-02-2018, 07:03 PM	#2
NCtoBRZ Senior Member Join Date: Nov 2017 Drives: 2017 Subaru BRZ PP WRB Location: Gulf Coast Posts: 383 Thanks: 71 Thanked 206 Times in 128 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Are you saying that it continuously oscillates? If so, that doesn’t sound normal. The voltage does fluctuate between 12-14 volts at different times though... but not a constant fluctuation.

07-02-2018, 09:05 PM	#7
Last Lemming Alive Member Join Date: Feb 2017 Drives: WRB 2017 BRZ Limited w/ PP Location: Louisiana Posts: 97 Thanks: 2 Thanked 49 Times in 19 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	I would have thought that revving the engine would have caused the voltage to peak not drop.

07-02-2018, 09:31 PM	#9
Last Lemming Alive Member Join Date: Feb 2017 Drives: WRB 2017 BRZ Limited w/ PP Location: Louisiana Posts: 97 Thanks: 2 Thanked 49 Times in 19 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	I tried looking at the service manual however it’s not very clear what is normal and not normal. It talks about what the battery voltage should be but not necessarily what the correct charging amps and voltage should be at any specific rpm Or how to test it without having hook up a computer to it For diagnosis.

07-02-2018, 09:57 PM	#10
Semiihcircle Member Join Date: Aug 2017 Drives: 17 BRZ Location: NY Posts: 60 Thanks: 10 Thanked 17 Times in 11 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	My BRZ does that too, im not too sure why. i cant even tell you when it happens, there is no set of particular conditions that occur when my voltage oscillates. but is not a constantly going from 12 to 14v and back to 12V. sometimes its just hanging out at 12V then jumps to 14V for a little while. there is no noticeable difference in ride. I just accept it as is, at this point. im also completely stock for now!

07-03-2018, 10:48 AM	#14
PhyrraM Senior Member Join Date: Aug 2012 Drives: '17 BRZ PP, old Legacy SSs and SVXs Location: Redlands, CA Posts: 119 Thanks: 34 Thanked 85 Times in 49 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	Perfectly normal for the 2017+. Turn on the headlights, it will stay at a steady high voltage.

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