So I finally found out how to access the hidden diagnostics menu (it's easier to get into Alcatraz). With the engine off the battery voltage reads 11.5v. Once I turned the engine on it generally displayed 13v but briefly dropped to 12.5v now and then. However after about 5 minutes on the road it remained at 12.5v and didn't update any more while the other parameters such as the speed updated constantly. Is this normal or could it be that the diagnostics program stopped getting voltage readings after a while? I read elsewhere that the running voltage should be 13v or even 14v so 12.5v seems low to me...

Voltage after starting engine:

I was using a voltmeter in the cig lighter socket. When the engine is running it should read 14.5V (approx) to begin with then dropping later to 13.5V (approx). When mine dropped to 12.0V I was concerned and took it straight to the dealer - only a couple of miles away. There were no warning messages. By the time I got there the slight burning smell which I noticed earlier was a lot worse. Dealer changed the alternator on the warranty I had fortunately taken out a few weeks earlier. I didn't change the battery as it didn't drain completely. All well now. 2012 5.0L S/C
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4.4 HSE
P38 4.6 HSE
Classic 3.9
90 County
Series3 Lightweight

Had a better reading on the way to work this morning. The voltage fluctuated between 12.5v and 13v after the first couple of miles but then settled at 13.5v for about half of my half-hour journey (mostly motorway). After slowing slightly in traffic it started fluctuating between 12.5v and 13v again until I parked up. Is that normal or should I definitely be seeing 14v while driving? Alternator and battery are both new. 2012 Vogue 4.4 TDV8 automatic (LHD), Santorini Black
2008 Vogue 3.6 TDV8 automatic (LHD), Java Black

Frank, do the same test with everything electrical turned on... The voltage should not fall lower than 13.5 with everything switched on... And should be somewhere closer to 14.5 normally sir...

I am sure the Diagnostics Menu gives low readings.

When I use an voltmeter I get almost 1v higher and at least 0.5v every time I compare it with the diagnostics menu.

can you get to those menus on older cars. i have a 2005 touchscreen

I think so. My understanding was that the above method worked from 2005 onwards though somebody should correct me if I'm wrong. I know models up to 2004 share the same on-board computer as the equivalent-aged BMW X5 for which there is a different procedure to access the dignostics menu (available here). 2012 Vogue 4.4 TDV8 automatic (LHD), Santorini Black
2008 Vogue 3.6 TDV8 automatic (LHD), Java Black


Last edited by FrankRizzo on 27th Aug 2014 11:34am. Edited 1 time in total

to get the secret menu on the touch screen FF's you press the middle top for about 4 seconds then press the nav button..you then should get a number key pad ,this is where you input the numbers 7,5,3.... ... - .- -.




Y. O. L. O.
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stan

that didnt seem to work for me, sure i am doing something wrong

is it documented anywhere, looked at the bimmernav stuff but thats for earlier models i think

its somewhere on the forum.


try it the other way round, nav screen then centre top... ... - .- -.




Y. O. L. O.
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I've tried both ways and all I get is a double beep and the screen remains blank.

ok , just did it on mine,

select the nav screen , press agree and no for destination,

press the house icon then press top center for a few seconds.. ... - .- -.




Y. O. L. O.
.

Found it on Utube. Touch top centre of home menu screen ,then top left and when screen changes enter 7..5..3

The alternator sounds weak. It should be at 15V when running. 12V points to a problem. HOWEVER, my mechanic said the onboard voltmeter was not very accurate and shouldn't be relied on. It's nice to give you an idea of where to look, but that's it.

Secret menu - cool. I will have to try that out.

Just to confirm: Once it's settled down (a couple of minutes) mine shows 14.5 -14.8v. This lasts for quite a while but once it's fully charged it will usually drop to 13.5v. If I then leave the vehicle for a while it will start again at 14.8v etc... This was the behaviour with my original alternator and is true again with the new one fitted a few weeks ago. I think this is the 'intelligent' charging process at work. Makes sense to me. 2012 5.0L S/C
Previous:
3.6 TDV8
4.4 HSE
P38 4.6 HSE
Classic 3.9
90 County
Series3 Lightweight