Charging System Fault

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Charging System Fault

Postby Peter704070 » Tue Jan 26, 2016 7:47 pm

Hello

I have a Peugeot 206 1.4 on a 2006 plate KFW engine which doesn't charge properly. Originally when I drove the car it was fine but then on a wet dark night the battery light came on. I switched the ignition off and the car wouldn't start. After 5 minutes it kicked back into life and off we went with no light on. We did a quick check and out a new alternator and battery on it.

At idle the alternator charges at 14.2 volts but when you switch everything on it drops to 12.2 volts. We've checked the earth cables and done some volt drop tests but the only issue we've found is with the control wire that goes from the alternator to the ECU this is a PWM signal which at full load on the vehicle should drop to 0 volts, but it doesn't it actually sits at 1 volt. I've included some scope patterns taken from the vehicle. I've used a four channel scope and looked at the following;

Battery voltage (Blue)
Control from the ECU to pin 2 on the alternator (Red)
Exciter wire from the BSI, this wire is also used to bring the warning light on (Green)
Current draw (Yellow)

I was lucky to have another 1.4 206 in the workshop so could scope that at the same time. The red pattern on one drops from 12 volts down to 0 volts. The other sits at 15 volts and drops to 1 volt. Why is this and where is that 1 volt likely to be from. I would use a wiring diagram but the Peugeot diagram shows it going to pin C4 on the black ECU plug. But that has no wire going to it. Any help would be great. Thanks Pete
Attachments
Peugeot With Fault.psdata
(14.98 MiB) Downloaded 97 times
Peugeot No Fault.psdata
(15.51 MiB) Downloaded 67 times
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Re: Chargning System Fault

Postby Peter704070 » Wed Feb 03, 2016 4:03 pm

Hello I've added a lot more information and hope that somebody can help. Pete
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Re: Chargning System Fault

Postby volrem » Wed Feb 03, 2016 6:06 pm

First capture shows channel B voltage between 1V and 15,3V. I'm concerned about that 15,3V while battery voltage stays at 14.3V.

Where are your channels grounded and what's the alternator voltage?

Also your sample rate is too high and timebase too low. Try something like 200ms/div and 1MS.

Remember you can always zoom in but not out.


Also measure alternator voltage, current and control signal while loads applied and voltage drops.
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Re: Chargning System Fault

Postby Peter704070 » Wed Feb 03, 2016 8:12 pm

Hello that's what concerns me in the first capture the voltage never drops below 1V - on the good pattern it drops all the way to 0V.

The ground is direct to battery with a good connection. We also checked for a volt drop at the battery connections.

Will change the sample rate and time base when I get the chance to scope it tomorrow.

Will put a load on the system and scope again. Driven the car again this evening with heavy rain, so had the wipers, rear screen, air con, lights and fan on setting 4. No warning lights came on.

Thanks for taking a look Pete
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Re: Chargning System Fault

Postby Steve Smith » Thu Feb 04, 2016 8:56 am

Hello Peter and Volrem, thank you for the posts and sorry for my late reply.

I am also intrigued by the voltage values between both vehicles.

The good vehicle has battery voltage above control voltage whereas the faulty vehicle has the reverse! (Battery voltage lower than control voltage)

I would like to know more about alternator load under these conditions and so would like to see current from the alternator to battery.

Could we also include the exciter/warning light circuit on our remaining channel and more time on screen as Volrem mentioned. (200 ms/div minimum)

Here we can see the activity of the complete system from idle no load, free rev no load, idle loaded and finally free rev loaded.

The idea here is to get an overview of the charging control under various load and speed conditions.

The best scenario would be to carry this out on the vehicle without any faults but we have to be realistic.

You mentioned volt drop tests, could you confirm this applied to the alternator charging cable form ALT + to Battery +

Just reading this through, can you take control of the control signal via a scan tool (Active test)?

Not sure if this vehicle has such a facility but we could see alternator response to independent control.

One final note, can we check the alternator response to disconnection of the control signal wire as with the case study below.

https://www.picoauto.com/library/case-s ... tion-error

This may implement a fail safe (machine sensed) voltage control from within the alternator, so assisting with diagnosis

Any feedback will be most interesting, take care.......Steve
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Re: Charging System Fault

Postby Peter704070 » Thu Feb 04, 2016 6:58 pm

Hello I've taken additional scope patterns this afternoon. Any help or an explanation would be great.

Thanks
Pete
Attachments
Peugeto 206 STARTING.psdata
(16.2 MiB) Downloaded 53 times
Peugeot 206 AT IDLE NO LOAD.psdata
(16.65 MiB) Downloaded 50 times
Peugeot 206 AT IDLE ALL CONSUMABLES ON.psdata
(16.63 MiB) Downloaded 49 times
Peugeot 206 3K REVS ALL CONSUMABLES ON.psdata
(7.86 MiB) Downloaded 52 times
Peugeot 206 3K NO LOAD.psdata
(17.28 MiB) Downloaded 54 times
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Re: Charging System Fault

Postby volrem » Thu Feb 04, 2016 8:29 pm

Hi


Since you haven't added channel labels please comment what channel is what.

I would also recommend to update your PicoScope software.
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Re: Charging System Fault

Postby Peter704070 » Fri Feb 05, 2016 8:48 am

Hello

Sorry I forgot to add the following information;

Blue - Battery voltage at the battery + and - negative terminals
Red - Control from the engine ECU to the alternator
Green - Current from the BSI to the alternator to excite it.
Yellow - Current reading taken from the positive wire at the battery

Volt drop on the Alt + to Battery + is 0.01v. Hope this makes sense Peter
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Re: Charging System Fault

Postby Steve Smith » Fri Feb 05, 2016 3:55 pm

Thank you for the continued posts and the psdata files, these are great for all to see.

Here we then have your vehicle performing as expected with no fault (Which I know is always the way)

Alternator output relative to load is good and the exciter circuit remains stable throughout.

It still begs the question as to why the control signal voltage level is greater than battery voltage and this must tie in with the ground that appears to float around 1 V (Channel B)

I would concentrate on this circuit and the component responsible for generating this control signal

How is this component grounded and what route does the ground take before termination at the chassis?

Thank you once again for the continued posts, any feedback would be most valuable as you continue to use this vehicle

Come to think of it, as its your vehicle, would it be possible to monitor this signal with your scope during various journeys looking for characteristic changes in battery voltage (use OBD pin) and control signal voltage.

Take care........Steve
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Re: Charging System Fault

Postby KimAndersen » Sun Feb 07, 2016 12:15 pm

Hi

I don't know if this will help in your diagnostic process.

I found a document which describes some of the problems you are struggling with in terms of the 1 volt offset, but it doesn't give any solution to this problem, other than to test a known good alternator.

ALTERNATOR TEST PROCEDURE.pdf
(532.19 KiB) Downloaded 132 times


Regards
Kim
Last edited by KimAndersen on Sun Feb 14, 2016 10:04 am, edited 2 times in total.
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