XR6T BATTERY VOLTAGE DROP UP AND DOWN ONLY ON IDLE

[XRBOY85]

Hi everybody

 

I have a bf xr6 turbo 6 speed and my battery voltage since I bought it on idle or coming to a stop in any gear will say go from 14.1v to 13.4/13.5v and then back up again

 

if I start driving it will go back to 14.1 and stay there as long as I do not slow down to a stop and when I do slow down coming to stop at the lights it will just stay at around 13.9 and 5 seconds later will drop to 13.4 and then again back up to 13.9/14.1 and same drop again until I start driving and then stabilize

 

it has a new alternator and new motorcraft battery from ford and the earth strapping seems ok

 

I have tested the voltage also directly from the battery on idle and not on my volts gauge and does the same thing every 5 seconds goes to 13.8/13.9 to 13.3/13.4 

 

any ideas or anyone had a similar issue and fixed it

 

any help would be great or info

 

thanks

[k31th]

is it causing any problems other than the numbers? they seem OK to me...

[Puffwagon]

I just pulled this out of my ass so take it with a grain of salt

 

Sounds like a smart alternator doing it's thing. Here's a pic of a Ford smart alternator (not necessarily an aussie falcon version) that demonstrates the alternator waveform with the engine at idle and the alternator at light load, then another at idle with moderate load. This is where I got the info from.

Blue= Alternator output current

Red= Alternator feedback signal

Green= Alternator command signal from PCM.