C3 Charging circuit diagram please Marc :)

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

User avatar
MikeT
Posts: 4628
Joined: 11 Jun 2007, 16:17
x 159

C3 Charging circuit diagram please Marc :)

Post by MikeT » 06 Oct 2018, 15:37

I'm sure you still have the VIN but just in case VF7**************[VIN obfuscated, can be read by forum staff]

If you'd be so kind as to post the relevant charging circuit diagram(s) and engine bay earth points I'd be most obliged.

And if anyone could advise some tests I could do as research shows it's probably not a failed alternator that's stopping the battery being recharged

User avatar
GiveMeABreak
Forum Admin Team
Posts: 11584
Joined: 15 Sep 2015, 19:38
x 989

Re: C3 Charging circuit diagram please Marc :)

Post by GiveMeABreak » 06 Oct 2018, 18:25

Give me a second Mike... here you go.

Image

Hell Razor5543
NOT Alistair or Simon
Posts: 8467
Joined: 01 Apr 2012, 09:47
x 501

Re: C3 Charging circuit diagram please Marc :)

Post by Hell Razor5543 » 06 Oct 2018, 21:06

I would start by checking the battery warning light hasn't failed. If it has, it stops the exciter circuit from working, which in turn stops the alternator from powering up and charging the battery.

User avatar
GiveMeABreak
Forum Admin Team
Posts: 11584
Joined: 15 Sep 2015, 19:38
x 989

Re: C3 Charging circuit diagram please Marc :)

Post by GiveMeABreak » 06 Oct 2018, 21:59

The battery warning light doesn’t stop anything. That just tells you if the alternator is charging or not. It lights with 12V from the battery with ignition on and therefore 0V from the alternator - the difference lighting the bulb, but when the engine is running and the alternator is working it produces arround 13 - 14V or thereabouts, similar to the battery, so as the difference is similar the light goes out.

Regardless, Lexia will show the voltages in the live data, so unless the slip rings have miraculously perished in that short a length of time, I think it will be something else.

User avatar
myglaren
Forum Admin Team
Posts: 14765
Joined: 02 Mar 2008, 14:30
x 345

Re: C3 Charging circuit diagram please Marc :)

Post by myglaren » 06 Oct 2018, 22:02

Hell Razor5543 wrote:
06 Oct 2018, 21:06
I would start by checking the battery warning light hasn't failed. If it has, it stops the exciter circuit from working, which in turn stops the alternator from powering up and charging the battery.

That was certainly true with regard to the Ford Scorpio James.
Perhaps that experience has taught engineers to use alternative methods.

wheeler
Posts: 3640
Joined: 21 Sep 2002, 19:07
x 60

Re: C3 Charging circuit diagram please Marc :)

Post by wheeler » 07 Oct 2018, 07:28

myglaren wrote:
06 Oct 2018, 22:02
Hell Razor5543 wrote:
06 Oct 2018, 21:06
I would start by checking the battery warning light hasn't failed. If it has, it stops the exciter circuit from working, which in turn stops the alternator from powering up and charging the battery.

That was certainly true with regard to the Ford Scorpio James.
Perhaps that experience has taught engineers to use alternative methods.

That would have been the case on old school charging systems, most modern ones are not like that. As you can see from the diagram above there is no direct connection from the alternator to the charging lamp, the IND wire goes from the alternator to the BSI via the under bonnet fusebox.
Whats the story with it then ? What makes you think the alternator has not failed? Have you tried measuring the charging voltage by putting your voltmeter negative directly on the casing & the positive straight on the main terminal on the alternator?

User avatar
xantia_v6
Forum Admin Team
Posts: 5794
Joined: 09 Nov 2005, 23:03
x 236

Re: C3 Charging circuit diagram please Marc :)

Post by xantia_v6 » 07 Oct 2018, 08:33

wheeler wrote:
07 Oct 2018, 07:28
myglaren wrote:
06 Oct 2018, 22:02
Hell Razor5543 wrote:
06 Oct 2018, 21:06
I would start by checking the battery warning light hasn't failed. If it has, it stops the exciter circuit from working, which in turn stops the alternator from powering up and charging the battery.

That was certainly true with regard to the Ford Scorpio James.
Perhaps that experience has taught engineers to use alternative methods.

That would have been the case on old school charging systems, most modern ones are not like that. As you can see from the diagram above there is no direct connection from the alternator to the charging lamp, the IND wire goes from the alternator to the BSI via the under bonnet fusebox.

Regardless of whether it comes via the warning bulb or the BSI, the alternator does need an excitation current in order to start charging. You should be seeing a small voltage (maybe as little as 2V) on the exciter wire.

User avatar
MikeT
Posts: 4628
Joined: 11 Jun 2007, 16:17
x 159

Re: C3 Charging circuit diagram please Marc :)

Post by MikeT » 07 Oct 2018, 13:27

Thanks for the diagram Marc. B03 to B01 (batt to starter) is obviously good, the engine starts no problem. BB1 to B01 (alt to starter) looks like it could be a fail point as could 1030 (to BSM) and 1087 (to BSI) along with both the BSM and BSI being points of failure. Then of course, there's the earths....


GiveMeABreak wrote:
06 Oct 2018, 21:59
Regardless, Lexia will show the voltages in the live data, so unless the slip rings have miraculously perished in that short a length of time, I think it will be something else.
I've barely looked at this car Marc so it may have come to me like this. The previous owner mentioned a new battery, but nothing about it not charging.
All I know is it would start and run after I repaired the Com2000 and BSI fault.
Six or so weeks later I find the battery flat - just after booking the MOT - so best I could do was charge the battery overnight so it could make the MOT appt in the morning.
Only when it was returned did I start investigating the flat battery cause and found it wasn't charging.


wheeler wrote:
07 Oct 2018, 07:28
As you can see from the diagram above there is no direct connection from the alternator to the charging lamp, the IND wire goes from the alternator to the BSI via the under bonnet fusebox.
Whats the story with it then ? What makes you think the alternator has not failed? Have you tried measuring the charging voltage by putting your voltmeter negative directly on the casing & the positive straight on the main terminal on the alternator?
I'm not ruling out a failed Alt but anecdotal evidence (via goggle) shows many a C3 owner having odd and failed charging issues which replacement alternators did not fix. Hence my plea for diagram and advise of best test procedure.

I will test as you advise wheeler, thanks.


xantia_v6 wrote:
07 Oct 2018, 08:33
Regardless of whether it comes via the warning bulb or the BSI, the alternator does need an excitation current in order to start charging. You should be seeing a small voltage (maybe as little as 2V) on the exciter wire.
Thanks Mike, I'll look for that also.
When I saw the diagram, my heart sank seeing the connection to the BSI as that was the cuplrit of the central-locking failure.

User avatar
MikeT
Posts: 4628
Joined: 11 Jun 2007, 16:17
x 159

Re: C3 Charging circuit diagram please Marc :)

Post by MikeT » 07 Oct 2018, 14:42

Can we link the flat battery (assumed excessive parasitic draw, which I was going to investigate next) in with this charging fault? The wiring diagram shows close relations so there could be a big clue on where to look?

User avatar
xantia_v6
Forum Admin Team
Posts: 5794
Joined: 09 Nov 2005, 23:03
x 236

Re: C3 Charging circuit diagram please Marc :)

Post by xantia_v6 » 07 Oct 2018, 15:06

It is possible that someone (lets blame the previous owner) has damaged the alternator by incorrectly connecting a battery in an attempt to jump-start the car.

User avatar
MikeT
Posts: 4628
Joined: 11 Jun 2007, 16:17
x 159

Re: C3 Charging circuit diagram please Marc :)

Post by MikeT » 07 Oct 2018, 15:26

I feel so silly now. Let me explain.
I went out to the car armed with a length of jumper wire and multimeter to do some tests. Battery was a lowly 12v to start and I knew this was last chance to start engine before having to remove it for another overnight charge.

Before starting the engine, I checked the battery (12.06v) to alternator casing voltage - 12.06v to positive and 0.00v to earth so no obvious losses there?
Then battery to alternator main post - again, 12.06v to earth and 0.00v to positive. Again, was a useful test?

Not knowing what else I could check at this stage (engine off) without having to remove parts or jack up the car to get underneath (ie access to starter motor etc) I tried starting the engine and it eventually fired up.

Interestingly, the battery light was not lit and the MM (at the battery) was showing about 11.5v and here's where it got weird (in a positive sense, I feel!)
I recalled reading a post during my research of one owner being instructed to rev the engine to 4K as "they all do that, sir" and sure enough his system started charging.
So I revved, tentively for a cold engine - 2K, nothing, 3K nope, 4k Bingo! 14.5v!
Allowed rpms to idle - still 14.4v
Turned on loads - lights, full beam, blower, hazards, radio - still pushing 13v or so, so all seemingly good in that respect?

So what's going here? The belt isn't slipping and it does seem it's an electrical switching change (presumably from the BSI?) that kicked it into life once sufficient revs are breached but 4K seems excessive for it to be intelligent design (but what do I know?).

User avatar
xantia_v6
Forum Admin Team
Posts: 5794
Joined: 09 Nov 2005, 23:03
x 236

Re: C3 Charging circuit diagram please Marc :)

Post by xantia_v6 » 07 Oct 2018, 16:00

Charging kicking in at high RPM is a good symptom of no excitation current to the alternator. The residual magnetism of the rotor eventually creates some excitation to get it started.

Is there a charging warning light on the dashboard, and what is it doing?

User avatar
EDC5
donor 2018
Posts: 1054
Joined: 01 Jul 2017, 21:48
x 79

Re: C3 Charging circuit diagram please Marc :)

Post by EDC5 » 07 Oct 2018, 16:09

Am I right in thinking alternators have a single brush in them to provide power to the coil?

Could it be that the high rpm caused it to rattle back to contacting the coreect place?

User avatar
MikeT
Posts: 4628
Joined: 11 Jun 2007, 16:17
x 159

Re: C3 Charging circuit diagram please Marc :)

Post by MikeT » 07 Oct 2018, 16:11

As mentioned above, the battery light was out with the engine running.
The exciter signal (or whatever it's called) is provided by the BSI (presumably as a direct logic control?) via the BSM as shown in the diagram (wire 1087 to 1030).

User avatar
EDC5
donor 2018
Posts: 1054
Joined: 01 Jul 2017, 21:48
x 79

Re: C3 Charging circuit diagram please Marc :)

Post by EDC5 » 07 Oct 2018, 16:17

I would have thought that the excitation current would be variable based on what the BSI/BSM deems necessary?