Changed Alternator, but still not charging??

S

sk93

Veteran
 Nottingham
changed the alternator out today, and after installation, I checked across the battery when the car is running, and I'm seeing 11.4v!?

What on earth is going on here.. its 12.6v at rest, but 11.4v when running.
The alternator was bench tested in front of me, so I know it's working, and the pully is very definately spinning when the car is running..... so why would I not be getting any charge?

Please someone help - I'm so gutted with my car right about now :(
 
You need to test the voltage directly out of the rear of the alternator.

Test from the B post.

Is it a new or second hand unit ?
 
At 11.4 volts the alternator is not charging your battery. Check the output from the alternator on the car to check that its giving the output volts of ~14v
If that is the case then the charge or higher voltage level is not reaching the battery.
I think you may have a bad earth or 'ground' has this been checked?
Never looked for it on the Z yet in the engine bay. Its worthwhile checking to take it off the list.
 
how would one check for a bad earth?
where would I start to even look?

I haven't checked the feed from the alternator as of yet, but will do tomorrow morning.
However, It was tested before I bought it, and the dash battery warning light is not iluminating..
 
I'll have a route around the engine bay tomorrow also and have a look myself and let you know my end. Interesting that the dash charging battery light is not illuminating.
:?
 
I think you are on the right track, having apparently eliminated battery and alternator I'd +1 on an earthing issue as the next thing to check, both engine earth and alternator earth. I'd trace, fully remove and clean both.
Just a thought... I remember seeing voltage recorded on the dash computer diagnostic functions so maybe there are fault codes for a failing component? obviously you need a code reader.

Over the years I've had several cars with these symptoms, and it's usually battery or earth or alternator. But I'v had one starter going open circuit and draining the battery when the car was stood, one with a dodgy locking module draining current all the time, one radio draining current and one chaffed loom in the engine bay. The point being that you need to carefully eliminate the obvious then get busy with a meter, removing fuses to isolate the problem circuit if it's not Alt, Bat, Earth.

Good luck and let us know how it goes :thumbsup:
 
Agree - I'd def be chasing down earth leads to ensure they are making a good circuit.
I'd start by using my jump leads to crate new one's to narrow it down. Engine to body. Body to earth terminal, etc.
 
I'll do that tomorrow then.. jump leads everywhere!

Was also thinking maybe the garage that replaced my clutch didn't reconnect something?
 
is it possible that the battery pyrotechnic disconnector has operated?

Are you measuring the battery terminals, or the major red cable that joins the disconnector?

This could be your problem (if it has one that is)
http://www.flickr.com/photos/71454676@N04/10899532276
 
ok.. more info.

The volts reading of the back of the alternator is just 0.65 volts!!?
How / why would that be the case? I know the alternator is/was working, as it was tested right in front of me before I bought it!

I have had a route around in the engine bay and cannot find any unconnected plugs or cables.
I also tried grounding the block to the body (using the ground terminal in the engine bay and a jump cable).
I then ran another cable from the same terminal in the engine bay directly to the ground on the battery.
This made no difference.

finally, I checked that cutoff switch thing and couldn't find any movement in the cable or terminal.
Is it safe to run a power cable all the way from the positive terminal on the battery to the positive jump point in the engine bay?
And if I do, will that remove the potential issue with the thing mentioned by Dario above?

I am so at a loss now and after all the expense already this month, can't afford to just drop the car at a garage tomorrow and let them fiddle with it :(
 
if you are not getting anything direct on the alternator connections it would appear to be that which is faulty, how was it tested/demonstrated to you

are you 100% certain your meter is correct, did you definitely have it on the right setting?
 
There is a grounding lead (engine earth) on the Off side front engine mount. Mine looks in good condition and is not open to much wear and tear (3.0 ) so not a high probability that this and issue
Another question
Does your battery charging light illuminate when the engine is off not running and clears when the engine is started and end engine running?
Start engine and check battery volts at the charging/jump point in the engine bay (NS Bulk head) an compare with the battery voltage level in the boot.
Has this issue started since the clutch was changed?
Did they correctly reconnect the lead from the alternator to the starter (at the starter motor end)? You will need to take the under tray off and look up. Difficult to see from the top down.
GL :thumbsup:
 
It was tested by being connected to a zed and a meter being connected across the battery and it showing 14 volts.

Positive my meter is correct.. set to read up to 20v DC
 
I believe the rectifier is integral to the unit... as in, it's the black box attached to the arse end of the unit.

Certainly, the power cable coming off the alternator seems to go straight into the main power loom.
 
The lead from the alternator should go down to the starter, connect to starter and then then another lead, connected at the same point on the starter goes back to the Jump point on the bulk head and then to the battery.
Trying to check whether the voltage levels are different at the bulk head and battery when the car is running.
 
Toe-side said:
The lead from the alternator should go down to the starter, connect to starter and then then another lead, connected at the same point on the starter goes back to the Jump point on the bulk head and then to the battery.
Trying to check whether the voltage levels are different at the bulk head and battery when the car is running.
Click to expand...

followed the cables and they are as you say.
voltage is 11.84v
 
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