Another alternator thread

[NomadicD3]

Hi All, I recently had an alternator related event from which I was able to ascertain some interesting information and maybe some advice about what to do should someone find themselves in the same situation. I have posted the full story in the “stories thread” for those whom have time to read the complete version however I thought I would post the pertinent details here.
In a fully operational 2.7 tdv6 the current draw whilst the engine is at idle is approximately 27amps, that is with the stereo on but no A/C or lights, add the A/C current draw is about 47 amps and with lights and HID spotlights on the current draw is just over 75 amps.
In the event of an alternator failure!!
The first alarm will be a loss of special programs then HDC, traction control and within a very short time the dash will light up like a Christmas tree. NB the battery warning light may or may not come on. The first alarm appears at about 11.5 volts.
As soon as all the lights come on pull over and remove the fuses for any unnecessary electrical accessories. Personally I disabled the stereo/GPS and the A/C.
Once this was done the vehicle only requires 30 amp at start up and immediately drops back to drawing only 6 amps whilst idling.
In my case with a 66amp/hr battery reading 10.5 volts I was still able start the vehicle and drive {limp} 75 km’s with the above systems disabled. With the same battery the next day reading 12.2 volts at the start of the day I was able to drive 150k’s before any warning lights appeared. The following day with three batteries connected {1x90 amp/hr and 2x 66 amp/hr} and all fully charged {starting voltage 12.97} I was able to drive 640 km’s, which included 1 stop start, at the completion of which the three batteries had 12.2 volts still remaining.
I personally believe that, in the event of an alternator failure, with a single 90 amp/hr primary battery fully charged and with the above mentioned systems disabled and I assume the vehicle still in some sort of LIMP mode, these vehicles are capable of driving in excess of 300 km’s without damaging the battery.
This information is derived purely from personal experience and with some very useful advice from Tim {Drivesafe} and in no way comes with any guarantees. It should also be noted that the vehicle had almost exactly 120 000km’s on the clock and seems to be the common number of K’s for those whom are experiencing alternator failures.
Hope this proves useful to anyone who may be unfortunate enough to go through the same event.
Happy travels all

[baldivistribe]

Thanks for posting the useful information. Do we know why the alternator failed 120000km doesnt seem very long. Is it heat/load related which reduces the service life of the alternator.
Cheers
steve

[NomadicD3]

Thanks for posting the useful information. Do we know why the alternator failed 120000km doesnt seem very long. Is it heat/load related which reduces the service life of the alternator.
Cheers
steve

Hmmm dam good question and probably one that Drivesafe may be able to answer for us. Due to a lack of time and forgetfullness I didn't think to get my hands on the old alternator and have it overhauled, but if I remember correctly someone else recently had the same issue and posted that they were going to have their old unit disassembled and the reason for failure sourced. Regardless, Tim maybe you could have an idea on this matter??
cheers

[Mully]

When mine carked it around 150 thou it showed an intermittent dash light for about 100 kms but the recurring suspension fault the alternator swap out fixed indicates a longer fault.... but without the dash light before final failure.

Always been curious about the ultimate reason for the alternator dying and seemed a bit like regulator breakdown perhaps... be interested to know what kills these alternators at such a young age but obviously there is a high electrical demand on the system in the D3.

Cheers.

[bbyer]

Yes, a good question - what fails in the alternator, and why.

It is not mechanical as say the bearings; the reason is I think, temperature.

I say that as I live in a cold climate area and the dealer says alternator failure is almost unknown here in Western Canada. We only use our AC about 60 times a year. In Eastern Canada, where probably the AC is in use 180 times a year, alternator failure is common.

I presume diesel engine compartments run cooler than petrol engine compartments, but the great equalizer is that most of your diesels are turbo charged, and that increases the heat generated plus your sunny warm desert climate adds to the concern.

In the D3 alternator, there are really only two items that may fail, (1) the diodes, (rectifier), or (2) the voltage regulator, the thing that accepts the PWM, (Pulse Width Modulated), signals from the ECM, (Engine Control Module).

I would like to think the heat sink in the rectifier is not big enough or does not get enough cooling and hence fails. The reason I like that idea is that I think somewhere there is a more robust rectifier part available that fits our Denso SC2 alternator.

I also doubt that there is a different voltage regulator that works as I expect the regulator is custom to the ECU whereas diodes are diodes.

If there is a more robust rectifier out there, then I think we would have a fix for the alternator. I understand the amp output of the D4 alternator is bigger than the D3 alternator, hence maybe a larger rectifier part does exist.