Technical Alternator only starts generating after revving

[nigelvan]

Yes, the behaviour is definitely different, the rpm drops back to normal after it starts at 1000 rpm. so no manual intervention is needed anymore.
Don't want to lamp test since apparently that could damage the L/D+ terminal according to some sources.

I dropped it already back on its four wheels so I won't do the test with L disconnected. We already tried with the Hitachi and there we saw the alternator wouldn't start without external input on L (in that case, a lamp indeed).

 

[koalar]

How long at 1000 rpm seconds minuites
How long before the alternator kicks in

 

[jackwhoo]

What a shame we will never know if BCM faulty or not if you don't disconnect it from L somewhere and examine alternator behaviour )-:

 

[nigelvan]

How long at 1000 rpm seconds minuites
How long before the alternator kicks in

Immediately when it hits 1000 rpm

 

[nigelvan]

What a shame we will never know if BCM faulty or not if you don't disconnect it from L somewhere and examine alternator behaviour )-:

I'll see if I can get to it without removing the plastic skid plate

 

[koalar]

Immediately when it hits 1000 rpm

Cheers

I was trying to work out the time frame, whether it was a coincidence alternators that have a soft start don't output anything for the fist 5-10 seconds

 

[nigelvan]

Cheers

I was trying to work out the time frame, whether it was a coincidence alternators that have a soft start don't output anything for the fist 5-10 seconds

I think it takes about that much time before the engine hits 1000 rpm. It does increments each 2 seconds or so.

 

[nigelvan]

What a shame we will never know if BCM faulty or not if you don't disconnect it from L somewhere and examine alternator behaviour )-:

Jack, just for you : disconnected L. Start the engine, immediate battery warning light, engine revs up, still 12V, I rev the engine up to 3000 rpm a few times: nothing happens, alternator stays dead.
So: BCM does make the alternator start, without it, it doesn't work

 

[jackwhoo]

Jack, just for you : disconnected L. Start the engine, immediate battery warning light, engine revs up, still 12V, I rev the engine up to 3000 rpm a few times: nothing happens, alternator stays dead.
So: BCM does make the alternator start, without it, it doesn't work

Thank you Nigel,
I have learned from this.....I bet you are happy too now you know BCM working correctly and can alert you to no charge situation.
Best wishes
Jack

 

[nigelvan]

Thank you Nigel,
I have learned from this.....I bet you are happy too now you know BCM working correctly and can alert you to no charge situation.
Best wishes
Jack

Nigel is the name of the van btw . I will only be happy if this keeps working. Remember last time when the old regulator suddenly started working again, only to fail again the next day...

I also learned from this. Yes, in hindsight just throwing a new alternator at it was probably a more sensible thing to do. Who knows how long until something else fails. On the other hand I learned about how these regulators work, how it used to work without computers. Found another interesting thing here.

I still don't know why it doesn't start right away. Why the old regulator suddenly worked again for one day... But, if this works I'm happy. At least I don't have the rev the engine anymore and attract attention on the parking lot...

 

[koalar]

I think it takes about that much time before the engine hits 1000 rpm. It does increments each 2 seconds or so.

It possible it's working correctly, normally you wouldn't have a multimeter on there to see it

It's got a load ramp and soft start

Without the full proper specifications and or someone with the same alternator it hard to be sure

a lot people with Audi and Renault have problems with alternators not starting unless they are rev'd, because they were fitted with two different types of alternators, either they have them rebuilt and the wrong regulator is fitted or they fit the wrong type

 

[nigelvan]

It possible it's working correctly, normally you wouldn't have a multimeter on there to see it

It's got a load ramp and soft start

Without the full proper specifications and or someone with the same alternator it hard to be sure

a lot people with Audi and Renault have problems with alternators not starting unless they are rev'd, because they were fitted with two different types of alternators, either they have them rebuilt and the wrong regulator is fitted or they fit the wrong type

Yes, it doesn't throw a battery warning light right away. And the fact that it does increase rpm on its own does indicate the behaviour was expected by the manufacturer. Still, it doesn't explain the fact why everything worked before, about a year ago. no increased rpm then. Maybe the new regulator isn't completely the same as the old one but I think that one is discontinued. At least we know the Hitachi wasn't the good one to use with this BCM on the L terminal.

 

[koalar]

On the Panda and most other Fiats
Battery warning is only looking for
below 4.5V at ignition on
above 5V when running


Need to keep an eye on this and see how it goes

 

[koalar]

Can you just double check this please, I know it was done earlier,

Multimeter on volts

Make sure you have good contact, you will probably have to extend you leads

Clean the top of the battery negative post
Clean a convenient spot of metal (Not painted) on the engine block

While cranking measure the voltage

Should stay below 0.2V but there is some leeway
Should be 0.0V as soon as you stop cranking

 

[AnthonyH]

Yes, in hindsight just throwing a new alternator at it was probably a more sensible thing to do. Who knows how long until something else fails. On the other hand I learned about how these regulators work, how it used to work without computers. Found another interesting thing here.

Dielectric breakdown is the most obvious cause of this problem, and not fixable. You can just drive the vehicle until the alternator dies and then replace it.

I still don't know why it doesn't start right away. Why the old regulator suddenly worked again for one day... But, if this works I'm happy. At least I don't have the rev the engine anymore and attract attention on the parking lot...

The dielectric breakdown will cause some of the windings to short and the alternator won't kick in without higher revs.

 

[nigelvan]

Can you just double check this please, I know it was done earlier,

Multimeter on volts

Make sure you have good contact, you will probably have to extend you leads

Clean the top of the battery negative post
Clean a convenient spot of metal (Not painted) on the engine block

While cranking measure the voltage

Should stay below 0.2V but there is some leeway
Should be 0.0V as soon as you stop cranking

Hi Koalar, I will test this probably next week when doing some more (cosmetic) work on the van. This is indeed a very good suggestion. I did test the drop between chassis and engine block yesterday as I had issues with a bad earth before. The voltage drop there was less than 0,02V but I didn't measure it while cranking. I added multiple extra earth wires back in 2021 I think, since the earth strap is notorious for going bad. Maybe it's a good idea to test the positive cable as well (between battery and starter).

 

[nigelvan]

Dielectric breakdown is the most obvious cause of this problem, and not fixable. You can just drive the vehicle until the alternator dies and then replace it.


The dielectric breakdown will cause some of the windings to short and the alternator won't kick in without higher revs.

Very interesting Anthony, thank you. Yes, this phenomenon could indeed explain (part of) the problem.
However, changing the regulator clearly made a difference. I did test the old regulator right before swapping it. This time the alternator didn't come out of the car so it wasn't subject to any shocks or other manipulations.
Could it be that de dielectric breakdown makes the regulator 'work harder' i.e. put more load/current on the field coils to compensate for losses, shortening the lifespan of the electronics inside?
I will indeed drive it until it fails, and then I will straight go to a new alternator. Lesson learned!

 

[Communicator]

Dielectric breakdown is the most obvious cause of this problem, and not fixable. You can just drive the vehicle until the alternator dies and then replace it.


The dielectric breakdown will cause some of the windings to short and the alternator won't kick in without higher revs.

Dielectric breakdown is just a posh way of saying insulation failure.
About 50 years ago when automotive alternators where relatively new, I retrofitted one to a Land Rover. Eventually the stator failed, I believe due to relative movement between two turns on one of the phases. On inspection the fault was obvious due to overheating of the windings. This is what will happen if there is a shorted turn(s) on the stator. The replacement stator was securely bound with linen thread, and varnished. No further problems during ownership of vehicle.

 

[AnthonyH]

Dielectric breakdown is just a posh way of saying insulation failure.
About 50 years ago when automotive alternators where relatively new, I retrofitted one to a Land Rover. Eventually the stator failed, I believe due to relative movement between two turns on one of the phases. On inspection the fault was obvious due to overheating of the windings. This is what will happen if there is a shorted turn(s) on the stator. The replacement stator was securely bound with linen thread, and varnished. No further problems during ownership of vehicle.

I can remember the days when it was possible to fix televisions and record players. It'd be good to return to a society where we fix things rather than replace them, but the intricate electronics in many items make this impossible nowadays.

One good thing that has happened is that computers were invented so that the components were plug and pay, meaning repairs are within reach of most people. It wouldn't be too hard for car manufacturers to follow a similar path if they were made to be government and legislators. I'd quite like to plug and play quite a lot more of my car components...

 

[vexorg]

You can still fix the alternator by getting it rewound, it will just cost more than a new one, so knock yourself out on that.

It is possible a few shorted turns will stress the regulator more, the alternator will be fighting itself slightly, and regulator work more for the same output. Stress out of limits to damage it, probably wouldn't have thought so.