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Discussion Starter #1
Hi all,
I've a model year 2011 Evoque L538 with 60,000 miles on the clock. I've been concerned for a while that the battery (possibly the original) was on its way out as Eco stop/start has never worked, the cruise control did not always work, the occasional low voltage warning on the dash etc.

However yesterday the car wouldn't start yesterday due to a the battery being completely flat and so I replaced it with a good quality 80Ah/800A CCA/AGM battery plus had the battery management unit reset by the garage.

All seemed well until I checked the battery voltage via the OBD port and noticed that with the ignition off the voltage was a healthy 12.7V but even on a fast tick-over, the running voltage struggles to maintain even a lowly 12.2V.

I'm suspicious that the alternator has failed but I'm mystified why the 'Charge System Fault' or red battery warning light has not come on - not even the MIL light and a stored code in the OBD.

Any thoughts? Fair enough if the alternator has gone on a 10-year old vehicle but why would the alarms not be showing?

Thanks in anticipation.
 

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Sounds like a dodgy alternator to me. Strange though that no warning has come up on the dash. Two things I would try, run the car and check the voltage which you say is 12.2, then switch on headlights, heater fan, air con etc and make sure battery voltage keeps getting lower as you switch more things on, proof that it definitely isn’t charging then perhaps unplug the alternator wiring and run the car and see if any warnings come up on the dash. Looks like a new alternator to me though.
 

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Discussion Starter #3
Trevor - many thanks for responding :)
Yes, done that by switching on the AC, heated seats, headlights etc etc to try to get the alternator to respond. No luck, all the load did was drive the voltage down further to 11.8V plus, after stopping the engine, the battery voltage had declined from 12.8 V (brand new fully charged AGM) to 12.6V.

Further question to all - I've read the Range Rover workshop manual and wondered if I could replace the alternator without removing the diesel fuel filter (hence avoiding having to re-prime it by bulb). Any thoughts?

Thanks again
 

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Not changed an alternator on an Evoque but taking the fuel filter off wouldn’t be a problem if you keep it upright and don’t lose the fuel out of it. It will still start if all you do is take the pipes off and then refit them.
 

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Discussion Starter #6
Great news - sorted!

I was preparing to change the alternator when I discovered that the alternator +ve lug was heavily corroded with part of the nut base completely missing - see pictures.

After wire brushing the alternator post, lug and nut plus liberally coating in copper grease, the car immediately started and shows 14.85V at the battery terminals!

If anyone has the same issue then I'd suggest that the electrical connections on the alternator are your first point of call!

Hopefully useful notes as follows;

1. Did an ECU reset by disconnecting the battery negative and pressing the brake pedal for 3 minutes = no effect at all - car started, no reprogramming required, no DTCs or MIL
2. Did an ECU reset by disconnecting the battery negative and positive and shorting the battery leads (not the battery posts!) together for 3 minutes = no effect at all - car started, no reprogramming required except clock, no DTCs or MIL
3. Checked continuity of red lead from alternator (B+) to battery positive lead (battery disconnected) and was a good 0.3 Ohm
4. After cleaning the alternator post, lug and nut car started with 14.85V at tick over (approx 900rpm) and with everything 'on' (heated seats, AC, audio, AC, rear screen heater, lights on full beam) the alternator output (measured across the battery) only declined to 14.80. Revving to 1500rpm produced no noticeable change in alternator voltage.
5. I can only conclude that a high resistance at the alternator battery post was enough to drop the voltage reaching the battery to the measured 12.2V. This would not have been enough to charge the battery and hence the continuously dropping battery voltage. This may also explain why the battery warning light and MIL/DTC did not see any issues (ie the alternator was producing the voltage asked of it but it was not getting to the battery terminals)

Hope this helps
 

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Glad it’s sorted, nice cheap fix. Looking at the photos to me it seems like the nut was lose and the power has been arching across rather than corrosion but maybe totally wrong.
 

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I'd agree with you there Trevor, looks like it's been arc eroding, if you get any more issues you should change that cable BBN.
 

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That also looks to me that it's been arcing, you need to take it off again strip back the red shroud to check the cable to lug connection to look for signs of heat damage.

Could also be heat damage back into the alternator !.

Hope you replaced the nut. !


On any cars you need to check your 'Earthing' points eg the place in which a cable goes to the body work of the car / vehicle, you will find that when the cars built the cable is bolted on to a painted surface, Paint being a good insulator. !


On our second car I changed the battery and while I was doing that took off the main battery to car earthing (or -ve) and cleaned off all the paint where it was bolted on, cleaned the lug, greased area, bolted up tight.


Michael, retired Electrical Scientist :)
 

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Discussion Starter #10
I'd agree with you there Trevor, looks like it's been arc eroding, if you get any more issues you should change that cable BBN.
Good recommendation - not sure if its been arc eroding (its only 12V) but could be heat damaged (melted) due to the alternator full output being of 160A being passed across a high resistance loose joint - possibly the M8 nut was only finger tight.
 

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Discussion Starter #11
That also looks to me that it's been arcing, you need to take it off again strip back the red shroud to check the cable to lug connection to look for signs of heat damage.

Could also be heat damage back into the alternator !.

Hope you replaced the nut. !


On any cars you need to check your 'Earthing' points eg the place in which a cable goes to the body work of the car / vehicle, you will find that when the cars built the cable is bolted on to a painted surface, Paint being a good insulator. !


On our second car I changed the battery and while I was doing that took off the main battery to car earthing (or -ve) and cleaned off all the paint where it was bolted on, cleaned the lug, greased area, bolted up tight.


Michael, retired Electrical Scientist :)
Michael - yes, I've replaced the nut with an M8 flanged nut (the existing nut has lost some of the flange and won't be compressing the lug evenly).

There's no sign of heat damage to the alternator (particularly of the B+ post as it enters the alternator body) or to the red battery cable and I've used a IR heat gun to check for a hot joint at the post.

Thanks
 
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