y heAlternator Problems!
Discussion
Hi all,
After replacing my alternator a couple of days ago due to the bearings going in the old one, my new one seems to not be charging the car...
I ordered a brand new unit from a TVR parts specialist and it looks identical to the old one so I simply swapped over the connections (only 3 of them). I noticed the car has been starting with less and less vigor so I just checked the alternator voltage and found it to be 10.5v with car off, 10.5 with car on.
A quick check reveals that the 100 amp fuse is intact, and there is 12v at the alternator big wire. What could be causing this? I've no idea where to start diagnosing this really?? Any help would be much appreciated as I kinda need the car tomorrow!
After replacing my alternator a couple of days ago due to the bearings going in the old one, my new one seems to not be charging the car...
I ordered a brand new unit from a TVR parts specialist and it looks identical to the old one so I simply swapped over the connections (only 3 of them). I noticed the car has been starting with less and less vigor so I just checked the alternator voltage and found it to be 10.5v with car off, 10.5 with car on.
A quick check reveals that the 100 amp fuse is intact, and there is 12v at the alternator big wire. What could be causing this? I've no idea where to start diagnosing this really?? Any help would be much appreciated as I kinda need the car tomorrow!
Hi Nick
I'm no expert but had exactly the same problem on a classic mini recently
4 alternators later and it was a short in the battery live cable,
the first one was putting out 10v, the second was putting out 16 volts,the third one had broken brushes.
these were all new alternators.
the fourth was a recon unit which charged fine with the correct voltages but the light would not go out thats how i found out about the short.
slideways
I'm no expert but had exactly the same problem on a classic mini recently
4 alternators later and it was a short in the battery live cable,
the first one was putting out 10v, the second was putting out 16 volts,the third one had broken brushes.
these were all new alternators.
the fourth was a recon unit which charged fine with the correct voltages but the light would not go out thats how i found out about the short.
slideways
450Nick said:
Thanks mate, where abouts was this short? from where to where??
It was the main red battery cable under the car the outer sheath had corroded and wire was touching the body work,probably not what is happening in your case you may have a dicky voltage regulator,you should be seeing between 13.5v to 14.5v at the battery when car is running at about 2000 rpm and under load, i.e all electrics on,the 12v your seeing is probably just battery voltage and the fact that it was hard to start before means wasn't getting a good charge
as i said, new doesn't mean its good, i would take it back and get another and hopfully eliminate a faulty alternator
Edited by slideways on Sunday 25th April 00:35
Edited by slideways on Sunday 25th April 00:41
If the car is starting off the battery then the lead to the battery is OK, I think from memory the battery goes direct to starter then short lead to 100A fuse then to alternator, so for a wire fault somewhere from starter to alternator.
As a quick test could you not start the car then disconnect battery as if alternator is working then car should continue to run.
As a quick test could you not start the car then disconnect battery as if alternator is working then car should continue to run.
chrispitman said:
As a quick test could you not start the car then disconnect battery as if alternator is working then car should continue to run.
This is a really bad idea that only used to work when cars had dynamos .................... if anyone on here is old enough to know what one is 
You can do all sorts of damage by not having the battery connected.
Ribol said:
chrispitman said:
As a quick test could you not start the car then disconnect battery as if alternator is working then car should continue to run.
This is a really bad idea that only used to work when cars had dynamos .................... if anyone on here is old enough to know what one is You can do all sorts of damage by not having the battery connected.
or something like that i think
I would still bet it's your 100 amp fuse.
How have you checked the fuse?
Take the cover off if it's still fitted and undo the screws that hold the fuse in it's holder and I bet the whole sorry business falls to bits.
Had the same symptoms and the fuse looked perfect but when pulled apart the fuse was cracked but not visible to the naked eye and it fell in two when the fixing screws were undone.
Paul.
How have you checked the fuse?
Take the cover off if it's still fitted and undo the screws that hold the fuse in it's holder and I bet the whole sorry business falls to bits.
Had the same symptoms and the fuse looked perfect but when pulled apart the fuse was cracked but not visible to the naked eye and it fell in two when the fixing screws were undone.
Paul.
Ah yes I'd forgotten about that one...! I'll check this when I get home. Although doesn't this supply the fusebox? In which case the car wouldn't run at all surely?. The one under the car by the starter I pulled the cap off and poked it with a screwdriver and it seemed absolutely fine so no worries there.
Also, the fact that the alternator does have 12v coming into it should indicate that the fuses are intact I think. So it must be the alternator? I've asked the supplier to send out a new one to test anyway so we'll see how that goes!
Also, the fact that the alternator does have 12v coming into it should indicate that the fuses are intact I think. So it must be the alternator? I've asked the supplier to send out a new one to test anyway so we'll see how that goes!
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