Any experience of partly failed alternator symptoms ?

Our 2006 3.6 TDV8 has been failing to start until "boosted" with increasing frequency.
Once the battery booster (NOCO unit) is attached for a few seconds, it starts instantly every time.
The battery is a Varta 020 that's approaching 3.5 yrs old & definitely weakening as it's only showing 12V occasionally prior to start-up & at its best maybe 12.5V - despite regular external charging via a CTek when the car isn't used for a few days.

Investigating what's going on has identified I've got a battery drain of approx 1 amp after system shutdown that isn't Entertainment / SatNav system related. I think 0.3A of this maybe the infamous Final Stage Resistor in the HVAC system & further investigation is underway to understand what else can be causing the remainder.

The alternator is draining some current, but it appears to be less than 0.02A - so not significant.
However, I've now noticed that sometimes after engine start-up, the system voltage is only climbing to 12.9~13.1V - even revving the engine.
Other times, the voltage immediately climbs to 12.9 or so & continues to climb over the next few seconds to 14.2V - which is more what I would expect from an OK alternator output.
PS there's no obvious whining noise from the alternator.

I know the battery is in need of replacement, but is the above another symptom of an alternator failing as well ?

My past experience of alternator failure has always been of instant total failure - with no intermittent variations.

Any thoughts ? Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

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Last edited by ur20v on 4th Oct 2021 7:09am. Edited 1 time in total

There's a few threads on TDV8 alternators. The 2007 vintage seems particularly fragile.

Some go with what appears to be no warning, but there's usually been a few clues leading up to it. Could be either - the problem is as above - I did exactly that, put a new battery in & a few weeks later it failed completely and killed the battery in the process. So my tip is buy one with a good warranty & keep the receipt - Euro Car Parts were very good, no quibble exchange

My alternator was failing for a couple of weeks - I suspected the battery at first but had a rude awakening on a dark Winter’s evening when I didn’t make it home due to complete failure of the alternator.
I monitored the voltage via the hidden menu for a few days and it fluctuated then made it to about 13 volts after a few miles.
By the time mine was going (on the day it expired) it was giving out about 11volts, leading to me not being able to engage Drive without using the manual release under the centre console when I tried and failed to make it home from work.

If you are going to bite the bullet and fit a new one yourself, do it soon while the weather is good. I did mine over 2 days just after Christmas, with near freezing temperatures.
Also, go for Denso, don’t be tempted by the cheaper one at Euro Car Parts. I did at first and noticed a difference in the position of the main terminal connector, adding a few more days to the job. 2017 Jaguar F Pace 25t Portfolio - still part of the JLR family 😀
2009 3.6 V8 (MY2010) - my first ever diesel! - now also gone
2004 4.4 V8 Petrol Vogue - now gone

my alterntor was fine until one day on a trip to york all the dash lights came one then total darkness and rolled to a stop. No other warnings at all, bit of an awkward job on the 3.6 aswell and cost me about 600 in the end iirc

Thanks guys - useful additional info !

Since the earlier post, the car has already failed to start once after a short journey with the alternator only producing 12.9V , but then charged fine at 14.2V on the following journey after being boosted.
It's definitely getting worse

Based on what you've said, I think I'm going to "bite the bullett" and replace the alternator as well as the battery.
Based on past experience & the suggestions I will go for the Denso unit. The existing part has lasted 16 years & my experience of other makes has not been positive.

I had to change the PAS pump & steering rack on the house driveway 18 months ago, so I'm probably equipped for the pain I've seen involved in changing the alternator

I'll report back when done !

Thanks again,
Paul Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

 2017 Jaguar F Pace 25t Portfolio - still part of the JLR family 😀
2009 3.6 V8 (MY2010) - my first ever diesel! - now also gone
2004 4.4 V8 Petrol Vogue - now gone

A failing battery or poor terminal contacts will do it as I found. Suggest clean tighten the distribution also (behind the battery)
and then you have to tell the car you have a new battery

Good Luck SOLD | Tuned MY 2011.5 Range Rover Autobiography 4.4 TDV8 Orkney Grey | e-diff | ACC

New Toy: Unimog U1550L/37
New : G350D

Has the car been programmed to accept new battery. There is a list on iid tool to select. I think this helps the alternator coordinate charge cycle times etc.

Landmark,
it's not needed on the earlier pre-AGM battery cars.

I've now changed the battery as it was failing to start so often despite being charged externally every night.
Prior to start up it was often only showing 11v

Interestingly, the charge voltage on start-up is now 14.2V everytime. No intermittent 13V charging.
It appears to suggest even the alternator needs more than 12V fed from the battery to make it work corectly & consistently ??

I haven't checked the battery drain values post shutdown yet to see if they'eve improved with more than 12V always available. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk