romanrob said:
OK, so what you are saying, is that it doesn't matter how old the alternator body is as long as it's all in good condition ? : o) Mine are 22 years old, including rectifiers, so I'm realistic as to condition
Click to expand...
As long as the insulation on the windings is in good condition and the slip rings are OK there is no problem. Windings can fail, but it's pretty rare. Of course it may be a good idea to change the bearings. Rectifier diodes (Diode pack) can be changed but semi conductors can fail young or old. Regulator failures are usually the brushes.
The alternator in my MR2 is probably 30 years old, it's second hand replacement as the original got full of water and froze solid, the one in the R11 is 36 years old, both still work fine.
 
Last edited:
Datatek said:
The set point is the fixed maximum voltage, it will go lower if the load is excessive but in normal circumstances the out put will always stay at the set point, it is the current that varies not the voltage unless the revs drop below the threshold required to meet the current requirements. My Transit puts out a constant 14.7 volts, my MR2 a constant 14.2 volts, wife's R11 a constant 14.2 volts. The regulator I removed from the P38 put out a constant 13.8 volts. I used to make money fitting smart regulators on boats, they would put out up to 15.8 volts dependant on battery and alternator temperature for a short period and then scale back as occurs with the Mobiletron.
Click to expand...
I am still struggling with my battery Hankook MF31-1000A which I fitted after reading on this forum. Now I read that for that battery the alternator set point should be 14.7V. My P38 setpoint is 14.2V. I also read that a voltage regulator set to 14.7V needs to be fitted. I tried the net but cannot find any voltage regulators. S how can I overcome this proble.
Help
 
lazbaz said:
I am still struggling with my battery Hankook MF31-1000A which I fitted after reading on this forum. Now I read that for that battery the alternator set point should be 14.7V. My P38 setpoint is 14.2V. I also read that a voltage regulator set to 14.7V needs to be fitted. I tried the net but cannot find any voltage regulators. S how can I overcome this proble.
Help
Click to expand...
When the engine is running what is the average output from the alternator. Mine will sit at around 14.2 and decline with minimum load on the battery.
 
Mark Piercy said:
When the engine is running what is the average output from the alternator. Mine will sit at around 14.2 and decline with minimum load on the battery.
Click to expand...
A few readings: 28/10/21: 11.94V first in the morning (engine stopped); engine idling 14.3v, dropping to 12.61v after 7-10 min.
9/10/21: morning 11.91v; idling 14.21v; 14.1v after 7-10 min
19/10/21: morning 12.0v; idling 14.2v; 14.16v after 7-10 min.
I do have some battery drain problem which I will try to eliminate in time.
However the battery should have been fully charged 12.6v and I am not sure it was. To keep the battery in good charged condition the charging voltage should ideally be 14.7V.
I have googled around how I can achieve 14.7V, alternator, voltage regulator etc I can find no answers.
Any help will be most welcome.
 
lazbaz said:
I am still struggling with my battery Hankook MF31-1000A which I fitted after reading on this forum. Now I read that for that battery the alternator set point should be 14.7V. My P38 setpoint is 14.2V. I also read that a voltage regulator set to 14.7V needs to be fitted. I tried the net but cannot find any voltage regulators. S how can I overcome this proble.
Help
Click to expand...
Mobiletron VR-VW010 is the regulator you want, find it on Ebay.
 
lazbaz said:
I am still struggling with my battery Hankook MF31-1000A which I fitted after reading on this forum. Now I read that for that battery the alternator set point should be 14.7V. My P38 setpoint is 14.2V. I also read that a voltage regulator set to 14.7V needs to be fitted. I tried the net but cannot find any voltage regulators. S how can I overcome this proble.
Help
Click to expand...
Mobiletron VR-VW010 is the regulator you want, find it on Ebay
 
lazbaz said:
A few readings: 28/10/21: 11.94V first in the morning (engine stopped); engine idling 14.3v, dropping to 12.61v after 7-10 min.
9/10/21: morning 11.91v; idling 14.21v; 14.1v after 7-10 min
19/10/21: morning 12.0v; idling 14.2v; 14.16v after 7-10 min.
I do have some battery drain problem which I will try to eliminate in time.
However the battery should have been fully charged 12.6v and I am not sure it was. To keep the battery in good charged condition the charging voltage should ideally be 14.7V.
I have googled around how I can achieve 14.7V, alternator, voltage regulator etc I can find no answers.
Any help will be most welcome.
Click to expand...

Anything over 14.3V should do the trick.
 
I have one of these mobiltron ones in my alternator, on startup it's 14.7 but soon drops, I've seen 13.2 on longer runs
 
As I understand it the regulator reads battery voltage from the main charge cable and a live feed via the smaller ring terminal. Comparing the 2 tells it how charged the battery is and therefore how much current to feed through the windings, which generates more / less charging current for the output. The initial excitation current is provided by the voltage feed via the alternator warning light. As charge is generated, that circuit comes to battery voltage from both sides, so the light goes out.
Therefore affecting the voltage the load wire delivers should affect the level of charge delivered. If you can drop the sensed voltage by half a volt, it will up the charging output to compensate.
However the voltage of the output is dependent on the internal rectification of the 3 phase output from the windings, which is a function of the root mean square of the phase difference voltage. Unless I have completely misunderstood the workings of car and motorcycle alternators and regulation for 30 odd years.
 
Scotiawhiskers said:
As I understand it the regulator reads battery voltage from the main charge cable and a live feed via the smaller ring terminal. Comparing the 2 tells it how charged the battery is and therefore how much current to feed through the windings, which generates more / less charging current for the output. The initial excitation current is provided by the voltage feed via the alternator warning light. As charge is generated, that circuit comes to battery voltage from both sides, so the light goes out.
Therefore affecting the voltage the load wire delivers should affect the level of charge delivered. If you can drop the sensed voltage by half a volt, it will up the charging output to compensate.
However the voltage of the output is dependent on the internal rectification of the 3 phase output from the windings, which is a function of the root mean square of the phase difference voltage. Unless I have completely misunderstood the workings of car and motorcycle alternators and regulation for 30 odd years.
Click to expand...
Yep what he said :rolleyes:
 
Scotiawhiskers said:
As I understand it the regulator reads battery voltage from the main charge cable and a live feed via the smaller ring terminal. Comparing the 2 tells it how charged the battery is and therefore how much current to feed through the windings, which generates more / less charging current for the output. The initial excitation current is provided by the voltage feed via the alternator warning light. As charge is generated, that circuit comes to battery voltage from both sides, so the light goes out.
Therefore affecting the voltage the load wire delivers should affect the level of charge delivered. If you can drop the sensed voltage by half a volt, it will up the charging output to compensate.
However the voltage of the output is dependent on the internal rectification of the 3 phase output from the windings, which is a function of the root mean square of the phase difference voltage. Unless I have completely misunderstood the workings of car and motorcycle alternators and regulation for 30 odd years.blah blah blah blah...
Click to expand...
ah, right then.
My understanding was...
Bolt it it on...
It works....
I'm happy.
It's quite a simple approach really involving less time to sit and think about it. Leaving more time to have a few beers..
:p;)
 
Scotiawhiskers said:
As I understand it the regulator reads battery voltage from the main charge cable and a live feed via the smaller ring terminal. Comparing the 2 tells it how charged the battery is and therefore how much current to feed through the windings, which generates more / less charging current for the output. The initial excitation current is provided by the voltage feed via the alternator warning light. As charge is generated, that circuit comes to battery voltage from both sides, so the light goes out.
Therefore affecting the voltage the load wire delivers should affect the level of charge delivered. If you can drop the sensed voltage by half a volt, it will up the charging output to compensate.
However the voltage of the output is dependent on the internal rectification of the 3 phase output from the windings, which is a function of the root mean square of the phase difference voltage. Unless I have completely misunderstood the workings of car and motorcycle alternators and regulation for 30 odd years.
Click to expand...
I'm not aware that the D+ line does anything other than provide the start up excitation current. Older regulators had a fixed reference voltage with no variation using a simple circuit comprising a voltage reference diode and a 2N3055 or similar power transistor to pass a variable current to the armature to maintain the output voltage at the reference voltage whatever the load current. The more uptodate regulators provide a higher voltage initially to provide a quick charge, with some the output is 17/18 volts initially, ideal for cars used on short run ( Range Rovers on the school run:rolleyes:). The regulator will function even with the D+ line disconnected, it only provides the initial excitation current
 
Datatek said:
Mobiletron VR-VW010 is the regulator you want, find it on Ebay
Click to expand...

I can find it on ebay as well as other places.
My question is will it fit on the alternator I have on the P38?
Alternator is 150 Bosch 0 123 520 022
NC> 14V 90-150A
ERR 3434
 

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lazbaz said:
I can find it on ebay as well as other places.
My question is will it fit on the alternator I have on the P38?
Alternator is 150 Bosch 0 123 520 022
NC> 14V 90-150A
ERR 3434
Click to expand...

The regulator VR-VW010 is for the dozzel engine
i believe the petrol's had a higher voltage then the dozzel to start with, others may know which part for the petrol.
 
brianp38dse said:
The regulator VR-VW010 is for the dozzel engine
i believe the petrol's had a higher voltage then the dozzel to start with, others may know which part for the petrol.
Click to expand...

I've got a feeling the early v8s had a smaller alternator with a 13.8V set point but then the later ones had a bigger one which possibly had a higher set point of 14.3V or 14.5V. the v8 ones are interchangeable. As long as you have a decent trickle charger and use it once or twice a year to keep the battery in good health that should be sufficient. As Data says, the more modern cars seems to be a lot cleverer and can go up to 17V before dropping down as required.
 
Why would the alternator on a diesel have a different set point to the petrol? It's the battery which cares, not the engine.
 
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