Technical Alternator only starts generating after revving

[jackwhoo]

I would love to agree with koalar but control /controlled in Europe often just means check or checked.

We call a person check point a check point - think east and west Germany.

The Germans and French call them control points.

I think there has been a miss translation of check to control.

I looked up the voltage regulator number and it is "old" technology . With a single set voltage regulation point.

 

[Pugglt Auld Jock]

Yes 9.5v open
Yes just over 1V ignition on
1.5K D+ to case
All appox

Should be around battery voltage while cranking
Which with the starter current will be around 10V


The BCM only sends current during cranking
Once the RPM is over 700 the current is cut

These are Regulated Voltage Control (RVC) alternators

The field current can be switched on and off via body computer very quickly, Fiat were one first to implement this technique (1985) whether your vehicle does or doesn't use it, I can't say elearn is very sketchy, then again the 500 does and it's not mentioned in elearn, I can't see why not the alternator runs cooler, and there's less drag from the alternator, improved MPG

Ah, that takes me up the knowledge ladder a few rungs - almost understand it now.

 

[nigelvan]

@koalar I'm pretty sure you can't control anything through D+ besides starting the alternating and measuring the voltage. There's another pin DFM or L pin that's not used on this model which tells you the duty cycle of the field coil, basically it's just connected to one of the brushes. The higher the duty cycle, the higher the load. Some cars will use this do increase the idle rpm when the computer sees the duty cycle is quite high and the alternator is under load.
Maybe this is what the computer on this model does too, seeying no or low voltage on D+...

The voltage regulator basically takes care of everything itself: load increases -> voltage drops -> put more juice on the field coil -> voltage raises again -> rpm increases -> voltage is higher -> less power to the field coils to get the voltage back to 14V. and so on...

 

[jackwhoo]

As you are going deep into this....I believe the voltage regulator powers the rotor field coils by a PWM signal varying to maintain the voltage set point.

 

[g8rpi]

The field control is "digital" i.e. on/off. For most it is effectively PWM but only fairly recent ones would have a "PWM controller" as a modern power electronics engineer would know it. A few are frequency modulated. The field current goes down with increasing frequency due to the winding inductance.
Even the old electromechanical regulators were "PWM" with a vibrating relay contact. Normally not fully on/off, there was a resistor across the contact when it was open. This helps reduce arcing of the contacts.
Don't get me started on brushless alternators and carbon pile regulators.....
I did design and build the alternator (400Hz AC output) regulator on the worlds fastest car

 

[vexorg]

Most battery bulbs for the alternator were more like 3-5W rather than 1.2W

 

[nigelvan]

Ok guys, back for another session of 'debugging'. Weird things happening:
Multimeter in voltage mode across D+ and GND. Everything connected as it should.

1st crank of the day: ignition on: 1.5-1.6V on D+, cranking the engine: drops to about 0, engine runs: stays 0, I rev the engine a bit and the alternator starts, D+ is now 14.6V. Computer is happy, idle rpm normal. This is the situation as it was before. 0V on the line tells either no power to the coil, or it's taking everything. The fact that revving the enging slightly starts the alternator indicates the field coil is at least partially powered.

I shut down the engine:

2nd, 3rd and 4th crank:

ignition on: 1.5V-1.6V on D+, cranking engine, stays 1.5-16V, engine starts, voltage stays the same. Alternator doesn't start. I rev the engine, nothing happens and computer puts on the battery light.
I now measure 50 ohm across D+ and GND with D004 connector disconnected, so BCM is out of the circuit.
I took the old regulator and checked the resistance there, it is 1.35K as @koalar mentioned.

Interesting fact is that it has rained and a lot of stuff is wet under the hood, and I started experiencing this problem in damp or wet weather... Next I'll run a patch cable all the way from the BCM to D+ withtout anything in between...

 

[koalar]

Are you saying you are measuring 50 ohms at the alternator

D+ to case

With connector disconnected D004

 

[jackwhoo]

Ok guys, back for another session of 'debugging'. Weird things happening:
Multimeter in voltage mode across D+ and GND. Everything connected as it should.

1st crank of the day: ignition on: 1.5-1.6V on D+, cranking the engine: drops to about 0, engine runs: stays 0, I rev the engine a bit and the alternator starts, D+ is now 14.6V. Computer is happy, idle rpm normal. This is the situation as it was before. 0V on the line tells either no power to the coil, or it's taking everything. The fact that revving the enging slightly starts the alternator indicates the field coil is at least partially powered.

I shut down the engine:

2nd, 3rd and 4th crank:

ignition on: 1.5V-1.6V on D+, cranking engine, stays 1.5-16V, engine starts, voltage stays the same. Alternator doesn't start. I rev the engine, nothing happens and computer puts on the battery light.
I now measure 50 ohm across D+ and GND with D004 connector disconnected, so BCM is out of the circuit.
I took the old regulator and checked the resistance there, it is 1.35K as @koalar mentioned.

Interesting fact is that it has rained and a lot of stuff is wet under the hood, and I started experiencing this problem in damp or wet weather... Next I'll run a patch cable all the way from the BCM to D+ withtout anything in between...

You should expect to see alternator output voltage on L pin when alternator working correctly- that is how the alternator turns off the charge light filliment bulb. When alternator charging both sides of the filliment are at the same voltage.

 

[jackwhoo]

Or if you have a complicated BCM controlled charge light , L voltage=alternator working output voltage signals BCM alternator is working.

 

[jackwhoo]

Do not assume field coil partially powered.
Residual magnetism of rotor will start alternator when sufficient rpms reached.

I have suggested connecting a small bulb to your wire from BCM to alternator and ground to test BCM and it's wiring capacity to provide current.

 

[jackwhoo]

Or just fit a suitable filliment bulb in a panel fitting via a switched live

 

[nigelvan]

Yes, the light trick works. It takes about 100mA to start the alternator
@koalar yes you read that correct, d+ to alternator case = 50 ohm
Putting a light between battery B+ 12V and d+ starts the alternator, takes 100mA, the same straight to the multimeter.
But, putting a 10W bulb (sorry, I don't have a wide collection, I am from the LED generation ) between B+ and D+ give 600mA of current, without engine running. With 50 ohm, should only be 240mA max (12V/50ohm = 0.24A)

I did a second test and it took now 700mA for the alternator to start... This seems too much as the BCM voltage collapses at 30mA. I have some experience with microcontrollers and this is a normal maximum amount of current for a IC pin to safely put out.

 

[vexorg]

You cannot measure ohms if there voltage on it

 

[nigelvan]

You cannot measure ohms if there voltage on it

Measured it directly between D+ pin and alternator case.

I think this is the problem: BCM can only supply 30mA but it needs more, way more. Now, we can say the BCM has an issue and I put a bulb in between an ignition powered wire and D+ and call it a day. But seeing how small this pin is and the wire going from the BCM to the D+ I don't think it was designed for more than what the BCM now supplies. Also the 50ohm between D+ and GND worries me, as it was clearly 1.35K before.

 

[koalar]

50 ohms isn't right. 1.35K is correct ish

It's unlikely going to start with the body control now

What's the part number of the regulator fitted


You original regulator should be lamp protect

But not all are but look similar for example F 00M 145 328

Description​

Specs 12 Volt, B-Circuit, L(RC)- F(FR) Terminals, 13.8 Default Vset For Bosch IR/IF Alternators Notes: *Vset controlled by vehicle RVC system. Without choke drive. L(RC) terminal is computer RVC(PWM) connection, not Lamp Regulator damage if tested as Lamp connection


If you are measuring direct on alternator pin and case there's only the new regulator module with any resistance between these points

 

[nigelvan]

50 ohms isn't right. 1.35K is correct ish

It's unlikely going to start with the body control now

What's the part number of the regulator fitted


You original regulator should be lamp protect

But not all are but look similar for example F 00M 145 328

Description​

Specs 12 Volt, B-Circuit, L(RC)- F(FR) Terminals, 13.8 Default Vset For Bosch IR/IF Alternators Notes: *Vset controlled by vehicle RVC system. Without choke drive. L(RC) terminal is computer RVC(PWM) connection, not Lamp Regulator damage if tested as Lamp connection


If you are measuring direct on alternator pin and case there's only the new regulator module with any resistance between these points

F00M 144 128 is the original Bosch regulator
Replaced with HUCO 130570, couldn't find the exact same part but multiple sites told me it was compatible.

It does start consistently with the lamp.

 

[nigelvan]

You cannot measure ohms if there voltage on it

Damn, I didn't realize even with D+ off I still have B+ with 12V on it, stupid me.

Ok, so alternator is off again, it isn't so bad if you know the tricks... Old regulator measures 1.35k, new reg measures 58k between D+ and case. I checked again and this part keeps showing up as an alternative for my old reg.
I also tested the rectifier diodes, 0.4V forward bias and 2.8-isch reverse. They all measure the same.
I tested the resistance of the rotor (now with a better multimeter) which is 3ohm all around.
Old reg has a diode or transistor/mosfet between D+ and GND: 0.6V forward bias. New part has not.

I did all measurements multiple times to be sure.
So did I kill the new part with the lamp test? Like I said, it still starts when I feed D+ through the lamp.
If I fed too high voltage to the base of a transistor it might be toast but still conduct.
On the other hand the part also didn't work prior to the lamp test. Maybe I got a bad part.
Just thinking out loud here...

 

[koalar]

Sorry can't find any technical info on the HUCO 130570

50 ohms or 58K

FOF fail on fit is a possibility

Old reg has a diode or transistor/mosfet between D+

That's normal on a computer controlled alternator

 

[nigelvan]

Well guys, I refitted the old regulator because I rather have to rev the engine than have nothing at all, first glued it back together with epoxy because I opened it.
It now just works... I just started 3 times in a row and the alternator fired right up.
The voltage at the connected d+ is back to 0,7V also while cranking. current draw 34mA with ignition on and while cranking.

My girlfriend just told me I look 'puzzled'..