K

Kaijun

Active Member
My disco broke down on M4 today, I pulled over with 3 amigos + HDC warning light+ two green lights (M+S) came up
with chime. I can not restart engine any more. road recovery took it my home, then recharging my battery, the engine can start but it stops once charging cable was disconnected. After it was charged some time, I can drive it to my parking space with those lights on and chime. Does it means my battery is totally dead?
Thanks!
Kai
 
Kaijun said:
Does it means my battery is totally dead?
Click to expand...
IMO yes, while the cause of the battery's death can be a failed alternator so measure the voltage at idle if you can start it and if it's below 14V fix the alternator before putting a new battery cos it will kill that too
 
SF will come on and tell you more detail, but the problem with starting from another car is that once the disconnection is made, if the starter car is running, its alternator suddenly stops reading a massive current draw, which ain't good for it. So its best to switch everything on on the starter car, i,e fans, lights, AC etc, so the alternator is already drawing a big current. Or simply turn off the ignition switch on the starter car before disconnecting, but it really isn't a brilliant idea to muck about jump starting if you know your own battery is absolutely dead. Just get a new batt. Easier in the long run. Unless you are out in the middle of nowhere I suppose.
 
Also it still won't do your own alternator any good trying to charge a dead batt which might even have a short circuit in it.
 
Kaijun said:
Thanks sierrafery! If I start it with another car, does it damage the battery of that car?
Click to expand...
If the rectifier pack is shot in your lternator that can cause damage to the other vehicle so as @Stanleysteamer said better fit a new battery start it and see the voltage and if it's low stop the engine and fix/replace the alternator... it will not kill the battery in such short time but it can hurt the aternator of the other car in no time
 
Is it possible to check if the alternator or its relevant part is dead with multimeter or other way without starting car?
 
IMO all empirical bench tests shown on youtube with multimeter are irrelevant unless the alternator is completely dead cos if it has a problem with the rectifier pack the ONLY way to rule it out is by using an oscilloscope otherwise it can pass the test on the output voltage and kill the battery with parasitic drain or ruin an ECU with AC spikes... that's why my reply about testing it with multimeter was "Not really"... believe me or not
 
Anything can fail not just the rectifier even though the rectifier or regulator are quite common failures it can be the winding interruption or brush issue as well... it's a guessing game without proper diagnose
 
Standard way to test an alternator is to get the car running, turn on all electrical items then check the voltage at the battery, it should read 14+ volts. If you've got your charged up/new battery on the car then start it and follow this procedure. If the voltage shown is less than 14v then you have a problem, which as @sieraferry said, could be a lot of things although brushes or diode pack are the most likely. I once took a faulty alternator off a minibus in a hailstorm in a French town, minibus full of students. Walked it a long way across town to a garage to get it tested. They told me to go back, put it back on, drive the van to them where they would test it on the vehicle! So I found all this out the hard way!
 
+1^^^ ... and even then, it can pass that load test on the vehicle and deliver good voltage while if only one diode is shot out of the 8 it will charge the battery well but it will kill it with parasitic drain while standing over night... hence the need of an oscilloscope and without that if an alternator is suspect the best way is to replace it with new or known good one which was removed from a well working vehicle.... empirical tests with multimeter are irrelevant for me and can lead to more trouble
 
I bought a car charger Ring RSC612 from halfords. It can analyze both battery and alternator https://www.ringautomotive.com/en/product/rsc612, attached document. The battery start power is 9V good, the capacity is 57% > bad 50%. But alternator tests indicates F07 error code,
poor functioning regulator. When I check voltage on battery, it indicates 12.5v on engine running. It is very likely the alternator is faulty, the battery can be changed. I don't know if there amigos are related to this, I have the three amigos issue intermittently. Any comments are welcome.
 

Attachments

  • RING_RESC612_BDA.pdf
    5.8 MB · Views: 258
  • image1.jpeg
    image1.jpeg
    40 KB · Views: 160
  • image2.jpeg
    image2.jpeg
    396.5 KB · Views: 174
First of all what battery do you have there cos 407CCA at 57% shows that it's weak from the beginning... as about the alternator test with that device(i have the same myself) i can say that it's very rudimentary but as long as you get 12.5V with engine running that alternator is fubar, might be just the regulator but that tool can't rule this out just like that.
 
I just stuck a whole alternator on mine and obviously got the new vac pump with it, seemed to make sense to do it as I plan to keep the car for a while. Have just fitted a 1000cca battery from Tanya that I found recommended on here and it bursts into life in a flash. Old battery was still functioning fine but needed one for the old D1 I’m selling so the D2 got the new one. From memory the amigos came on first when it was dying then everything else.
 
Last edited:
sierrafery said:
First of all what battery do you have there cos 407CCA at 57% shows that it's weak from the beginning... as about the alternator test with that device(i have the same myself) i can say that it's very rudimentary but as long as you get 12.5V with engine running that alternator is fubar, might be just the regulator but that tool can't rule this out just like that.
Click to expand...

I have Varta battery changed in Germany see pic. I chosed 700 CCA
 

Attachments

  • image1.jpeg
    image1.jpeg
    396.7 KB · Views: 153
You must log in or register to reply here.

Similar threads

sonicm1etn
intermittent completely dead fault TD5 D2
Replies
7
Views
455
Shedload
S
MrGorsky
P38A Service Brake right on the MOT limit...
Replies
10
Views
347
roythebus
R
B
Discovery 4 2015 auxiliary battery Question
Replies
9
Views
2K
Graculus
Graculus
G
Disco 3 (LR3) Having a nightmare Discovery 3 (2007)
Replies
17
Views
1K
gawjie
G
H
Discovery Sport Sept 2015 - Breakdown
Replies
14
Views
2K
Phil-G
P