I did a diode check in forward bias but nothing. The results of the multimeter do not give away that there's a diode in the circuit. I'll do some more testing once I thoroughly clean the D004 pins as there is still some green muck on them.
Technical Alternator only starts generating after revving
- Thread starter nigelvan
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Technical Alternator only starts generating after revving
Normally on modern alternators
All the windings come to connectors on the back
And one integrated module regulator and diodes just bolts on, Which are less than £30
Getting the correct part will be more difficult, you will need the exact model number of the alternator fitted
It's likely to be an internal short inside something like this
Yep get that green muck out
You have 10V it been pulled down to 0.7V via the resistance in the alternator, there no diode in-between just a wire. We seem to have got obsessed with fact it happens to be 0.7V mine happens to be close to 1 volt but I have much higher resistance
We just need someone to measure their Ducato alternator from the D004 connector
Every alternator I have tested have been around 1.5K I don't have a Ducato to test otherwise I would go out and test it
What output voltage is the alternator producing once it is running? The 30 ohm value to qround certainly looks like an alternator fault. I assume thet as pointed out by Vexorg that you are not using a DMM and NOT in diode test mode.Robert
The field circuit is normally a diode from one output winding to one side of the field winding (via brushes and slip-rings) and tha D+ (exitation / warning lamp) terminal. The other side of the field winding goes to common via a transistor the controls the current and thus output voltage. To get 30 ohms it is likely that either the diode or transistor is short circuited.
If the E-learn diagrams are to be belived both the diode and transistor are in the regulator module. This probably also integrates the brush holder and brushes. These are normally available as a service part. Yo probably need the full part nu,ber of the alternator to make sure you get the right one. It is often possible, or even easier, to change the reglator module without removing the alternator.
Completely random ebay example www.ebay.co.uk/itm/275989389440?
Robert.
The field circuit is normally a diode from one output winding to one side of the field winding (via brushes and slip-rings) and tha D+ (exitation / warning lamp) terminal. The other side of the field winding goes to common via a transistor the controls the current and thus output voltage. To get 30 ohms it is likely that either the diode or transistor is short circuited.
If the E-learn diagrams are to be belived both the diode and transistor are in the regulator module. This probably also integrates the brush holder and brushes. These are normally available as a service part. Yo probably need the full part nu,ber of the alternator to make sure you get the right one. It is often possible, or even easier, to change the reglator module without removing the alternator.
Completely random ebay example www.ebay.co.uk/itm/275989389440?
Robert.
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Trying to thing what I would do if it was my van
Still with D004 disconnect
I'd unbolt the D+ and measure the resistance between its case and the D+ terminal
And the yellow and red wire to chassis ground
And while I was there I take a photo of model number
Whichever has the 30 ohms is likely to be the problem, it's more likely to the alternator, but why guess
We know all the windings are working as once going it's fine, assuming the bearings are fine I'd order a new regulator module from the photo earlier
Still with D004 disconnect
I'd unbolt the D+ and measure the resistance between its case and the D+ terminal
And the yellow and red wire to chassis ground
And while I was there I take a photo of model number
Whichever has the 30 ohms is likely to be the problem, it's more likely to the alternator, but why guess
We know all the windings are working as once going it's fine, assuming the bearings are fine I'd order a new regulator module from the photo earlier
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@g8rpi I did use a digital multimeter in resistance mode and in diode test mode. I seem to have missed that comment from Vexorg?
The output voltage is otherwise normal (above 14V) and I have no problem charging the battery or powering any electrics. So the voltage regulator seems to be doing its job. So it either takes power from D+ (the BCM) or one of its own windings to power the field coil. If both pass through the same circuit those seem to be fine, as the voltage regulator does its job. Maybe the field coils is partially shorted which would explain why the BCM can't power the field coil enough to get it started but the voltage regulator can once it can take as much power as it wants from the winding coil? Anyway that's just guessing. I need to get down to the alternator and investigate further as @koalar points out.
We did establish the resistance is too low which explains the 0.7V instead of 1V so a fault in the wiring is very unlikely it seems.
The output voltage is otherwise normal (above 14V) and I have no problem charging the battery or powering any electrics. So the voltage regulator seems to be doing its job. So it either takes power from D+ (the BCM) or one of its own windings to power the field coil. If both pass through the same circuit those seem to be fine, as the voltage regulator does its job. Maybe the field coils is partially shorted which would explain why the BCM can't power the field coil enough to get it started but the voltage regulator can once it can take as much power as it wants from the winding coil? Anyway that's just guessing. I need to get down to the alternator and investigate further as @koalar points out.
We did establish the resistance is too low which explains the 0.7V instead of 1V so a fault in the wiring is very unlikely it seems.
Hello guys, I'm back. The weather has been **** up until now. But today was a great day to remove an alternator.
Actually the hardest part was getting wrenches, ratchets into the small area. Took the pressure of the belt tensioner and took off the belt from the alternator pulley. Took off the B+ and D+ cables and removed the 2 bolts holding the alternator into place. Then used an extention and a hammer tap it in order to loosen it from the bracket. Actually getting the alternator out is super easy: if you just lift it over the suspension and steering rack towards the back you can just take it out next to the exhaust, lots of space. No need to remove the power steering cover as eLearn instructs.
Anyway I think this alternator is from 2017, as the unit shows 10/17 and the plastic regulator shows the small stamp pointing to 10 and 15 in the middle.
I've added some pictures. I forgot my multimeter so no resistance measurements yet. The brushes are still more than long enough to touch the rotor contact.
Now what's next? I could try and throw a new regulator in for € 20... A new alternator is about € 140 now. But as you know, the alternator still works after raising the rpm a bit. If I knew the correct resistance for the exciter coil I would have some data to work with...
Actually the hardest part was getting wrenches, ratchets into the small area. Took the pressure of the belt tensioner and took off the belt from the alternator pulley. Took off the B+ and D+ cables and removed the 2 bolts holding the alternator into place. Then used an extention and a hammer tap it in order to loosen it from the bracket. Actually getting the alternator out is super easy: if you just lift it over the suspension and steering rack towards the back you can just take it out next to the exhaust, lots of space. No need to remove the power steering cover as eLearn instructs.
Anyway I think this alternator is from 2017, as the unit shows 10/17 and the plastic regulator shows the small stamp pointing to 10 and 15 in the middle.
I've added some pictures. I forgot my multimeter so no resistance measurements yet. The brushes are still more than long enough to touch the rotor contact.
Now what's next? I could try and throw a new regulator in for € 20... A new alternator is about € 140 now. But as you know, the alternator still works after raising the rpm a bit. If I knew the correct resistance for the exciter coil I would have some data to work with...
Highly unlikely to be the rotor given the symptoms. Get a new regulator pack.
Measure the resistance of your test leads first
Typically 3-6 ohms for the centre field winding
Each.of the stators three phase should all be around the same, and about 0.5 ohms
All together it's about 1.5K ohms D+ to the case
That what I get on the alternator on the the Puntos and Pandas, I suspect this will be the same
Typically 3-6 ohms for the centre field winding
Each.of the stators three phase should all be around the same, and about 0.5 ohms
All together it's about 1.5K ohms D+ to the case
That what I get on the alternator on the the Puntos and Pandas, I suspect this will be the same
I measure just below 3 ohms for the centre field winding. phases are about 0.1-0.2 ohm . D+ to case is about 1.35K Ohms. I'm going to see what I can find about this Bosch alternator. With 140A it might be a bit heavier than those of Puntos/Pandas?
3 ohms is correct for the centre
Looks like your meter reads slightly lower than mine mine normally measures about 4
Following this I get around 0.3 to 0.4 and yours is again slightly lower
As long as each phase measures the same
No phase shorts anywhere
No field short anywhere
I would be happy call a regulator, without out going any further
We know the windings are working as it kind of works
The only thing wildly different is the 200k less between. D+ and case
So, I'm waiting on a new regulator. I couldn't find the exact same one for Bosch but I ordered one from Hitachi. It should be compatitble. At least it looks the same and has the same voltage rating...
Anyway, the rest of this message is just me playing around with the existing voltage regulator trying to understand the inner workings. I actually opened up the plastic case on the regulator and found some kind of IC inside which I've never seen before... So I put it under my microscope...
I also connected each winding to my oscilloscope and saw a nice sinus wave when I turned the rotor. So those should be fine.
I also learned more about the DFM pin, not used by the BCM of the Ducato, next to the D+ pin. This shows the duty cycle of the DFM (the rotor field) and is used by some cars to determine the load on the alternator at a given rpm.
Now, actually we can learn a lot about the mention of 'duty cycle'. This actually tells us the magnetic field of the rotor coil, or the exciter current is actually a PWM signal and not some fixed DC signal.
So, I think this explains the open voltage of 10V from the BCM to D+, and 1V when ignition is on (and the 0.7V I actually measured), since it's a PWM signal this is an average voltage. There is a diode between D+ and the top brush going to the slip rings with a forward voltage drop of 0.6V (on my old regulator). So measuring 0.7V instead of 1V when the BCM powers the rotor leads me to believe some current is leaking to the case or gets dissipated somewhere and not going through the coil... Causing the alternator to not fire up like it should. But on the other hand... when it fires up the regulator does it job at keeping the voltage stable at 14.4V...
It's not easy to 'debug' this out of the car and without a power tool to spin the alternator fast enough. We'll see when the new regulator arrives and I put everything back into the car and fire up the engine. I'll test the terminals of the new unit to compare it to the existing measurements.
Yes, I know I went into a rabbit hole which left me with more questions than I had before, like why does it work perfectly when it feeds off its own B+ power, but not from D+?
Anyway maybe this information is useful to someone in the future.
Anyway, the rest of this message is just me playing around with the existing voltage regulator trying to understand the inner workings. I actually opened up the plastic case on the regulator and found some kind of IC inside which I've never seen before... So I put it under my microscope...
I also connected each winding to my oscilloscope and saw a nice sinus wave when I turned the rotor. So those should be fine.
I also learned more about the DFM pin, not used by the BCM of the Ducato, next to the D+ pin. This shows the duty cycle of the DFM (the rotor field) and is used by some cars to determine the load on the alternator at a given rpm.
Now, actually we can learn a lot about the mention of 'duty cycle'. This actually tells us the magnetic field of the rotor coil, or the exciter current is actually a PWM signal and not some fixed DC signal.
So, I think this explains the open voltage of 10V from the BCM to D+, and 1V when ignition is on (and the 0.7V I actually measured), since it's a PWM signal this is an average voltage. There is a diode between D+ and the top brush going to the slip rings with a forward voltage drop of 0.6V (on my old regulator). So measuring 0.7V instead of 1V when the BCM powers the rotor leads me to believe some current is leaking to the case or gets dissipated somewhere and not going through the coil... Causing the alternator to not fire up like it should. But on the other hand... when it fires up the regulator does it job at keeping the voltage stable at 14.4V...
It's not easy to 'debug' this out of the car and without a power tool to spin the alternator fast enough. We'll see when the new regulator arrives and I put everything back into the car and fire up the engine. I'll test the terminals of the new unit to compare it to the existing measurements.
Yes, I know I went into a rabbit hole which left me with more questions than I had before, like why does it work perfectly when it feeds off its own B+ power, but not from D+?
Anyway maybe this information is useful to someone in the future.
Well you have at least confirmed the regulator is toast! Your second photo shows significant damage. I wonder if it is the excitation diode.
Robert.
Robert.
The damage is only to the coating on top of the ic, it's my doing because it touched it. It's some kind of soft silicon
So, after 10 long days the new voltage regulator finally arrived. After 2 hours of swearing I got the alternator back in and... the issue is still there and has even gotten worse. At first it seemed the alternator was completely dead now but I managed to get it going (off residual magnetism... which is probably even lower after all the tinkering with it) once when I revved over 3000 rpm. Then I got a steady 14.2V. So it seems this new regulator and the old one were doing their job, and so is the entire alternator again. Next I'll recheck all wiring and voltages, resistance... and try to get the alternator going with injecting 12V into D+ manually through my DMM.
So that looks like a loss of excitiation from the BCM. As I suggestd before, connect a small filament lamp (like a panel or linstrument cluster bulb) of less tha 3.5W between D+ and ignition switched +12V supply.
Not only will this confirm the fault (BCM or just possibly wiring) it will provide a low cost fix.
Robert.
Not only will this confirm the fault (BCM or just possibly wiring) it will provide a low cost fix.
Robert.
Ok, so I got a bit further but first answers to your questions:
So, I was considering pulling the alternator out again and decided to rule out any wiring issues despite not measuring any resistance between the D004 connector and D+, and the D004 and the BCM under the dash. I then did feed 12V from the battery + next to the relay box into the D004 connector and the alternator fired up. I also bridged the wire between the 2 sides of D004 to rule out any issues in the connection there.
With the ignition on I measure 9.5V on the D+ wire with the connector off the alternator, plugged in I now get 1.6V. Before, with the old regulator, I got 0.7V so this is quite a difference. Also, with the old regulator revving the engine slightly would start the alternator, with the new one, that doesn't work and I do get a battery warning light after some time. So this is odd...
So, next thing I want to do is take the BCM connector apart and reconnect it without the outer housing, this way I can get a needle in the D+ pin hole and run a patch cable straight to D004. If this works and fires up the alternator then I'll have to run a new wire to fix it and then the alternator has nothing to do with it in the end...
Option 2 is that the alternator is faulty on the rotor or stator coils and the BCM can't provide enought current to get it going, but putting 12V on it can start it...
I had to stop looking into it today but will probably continue tomorrow or Friday.
Yes, this works and starts the alternator. But I tried it with just 12V, no lamp in between. Through the multimeter it didn't work, it is faulty (probably blown fuse), but I will try again with another one. The problem with this fix is that I will not get a warning light when the alternator fails in the future because there will always be 12V on the
I did, when I put all lights on and put the blower at max the voltage did drop to about 13.8-13.9V with the new regulator. Otherwise it will stabilize around 14.2V.
No, only D+ to the BCM. There's no cable to the ECU, not according to the schematics, probably the newer models do use this.
So, I was considering pulling the alternator out again and decided to rule out any wiring issues despite not measuring any resistance between the D004 connector and D+, and the D004 and the BCM under the dash. I then did feed 12V from the battery + next to the relay box into the D004 connector and the alternator fired up. I also bridged the wire between the 2 sides of D004 to rule out any issues in the connection there.
With the ignition on I measure 9.5V on the D+ wire with the connector off the alternator, plugged in I now get 1.6V. Before, with the old regulator, I got 0.7V so this is quite a difference. Also, with the old regulator revving the engine slightly would start the alternator, with the new one, that doesn't work and I do get a battery warning light after some time. So this is odd...
So, next thing I want to do is take the BCM connector apart and reconnect it without the outer housing, this way I can get a needle in the D+ pin hole and run a patch cable straight to D004. If this works and fires up the alternator then I'll have to run a new wire to fix it and then the alternator has nothing to do with it in the end...
Option 2 is that the alternator is faulty on the rotor or stator coils and the BCM can't provide enought current to get it going, but putting 12V on it can start it...
I had to stop looking into it today but will probably continue tomorrow or Friday.
NigelVan said:
"Yes, this works and starts the alternator. But I tried it with just 12V, no lamp in between. Through the multimeter it didn't work, it is faulty (probably blown fuse), but I will try again with another one. The problem with this fix is that I will not get a warning light when the alternator fails in the future because there will always be 12V on the"
If you use a panel lamp and put it in the dash you will get a failure indication. At the moment you are looking at a BCM replacement / repair.
A direct connection is not ideal as it might damage the regulator. It won't work with the DMM on volts because it will not pass enought current. You could use a a LED with two resistors and a diode.
Robert.
"Yes, this works and starts the alternator. But I tried it with just 12V, no lamp in between. Through the multimeter it didn't work, it is faulty (probably blown fuse), but I will try again with another one. The problem with this fix is that I will not get a warning light when the alternator fails in the future because there will always be 12V on the"
If you use a panel lamp and put it in the dash you will get a failure indication. At the moment you are looking at a BCM replacement / repair.
A direct connection is not ideal as it might damage the regulator. It won't work with the DMM on volts because it will not pass enought current. You could use a a LED with two resistors and a diode.
Robert.
