Alternator D+ / 61 Terminal

[nigel1]

Volvo Penta TMD22 with uprated 100 Amp alternator

Been having issues with alternator ever since having fitted a Sterling external regulator (which turned out to be defective).
External reg has been removed, and Sterling sent a replacement, not yet fitted.

I measured only 4 volts at the D+ terminal, I think it should be closer to battery voltage. Initially thought the alarm module might have been the cause. I swapped it out with a second hand unit, said to be tested and good. With the replacement module in place, igntion key at first position, voltage at D+ was 4.8V. I removed the ignition feed from the D+ terminal, and voltage measure at the ignition feed ring terminal was 13.6V (same as battery voltage), when connected back on D+, voltage drops to 4.8.
Starting the engine, the alternator usually comes to life, but not always. (Alternator output is to a split charging diode)

The uprated alternator is new, fitted about two months ago, and worked fine when tested after installation. Things only got bad after fitting the external regulator.
(failed to control output voltage)

Can some one confirm that the D+ voltage should be same as battery voltage with ignition on, but engine not running.
Could some damaged component in the alternator cause this voltage drop,?

Next test is to refit the original 60 amp alernator and check the voltage at D+, but that wont be until next week.

Cheers
Nigel
And a Happy New Year to all

 

[PaulRainbow]

Volvo Penta TMD22 with uprated 100 Amp alternator

Been having issues with alternator ever since having fitted a Sterling external regulator (which turned out to be defective).
External reg has been removed, and Sterling sent a replacement, not yet fitted.

I measured only 4 volts at the D+ terminal, I think it should be closer to battery voltage. Initially thought the alarm module might have been the cause. I swapped it out with a second hand unit, said to be tested and good. With the replacement module in place, igntion key at first position, voltage at D+ was 4.8V. I removed the ignition feed from the D+ terminal, and voltage measure at the ignition feed ring terminal was 13.6V (same as battery voltage), when connected back on D+, voltage drops to 4.8.
Starting the engine, the alternator usually comes to life, but not always. (Alternator output is to a split charging diode)

The uprated alternator is new, fitted about two months ago, and worked fine when tested after installation. Things only got bad after fitting the external regulator.
(failed to control output voltage)

Can some one confirm that the D+ voltage should be same as battery voltage with ignition on, but engine not running.
Could some damaged component in the alternator cause this voltage drop,?

Next test is to refit the original 60 amp alernator and check the voltage at D+, but that wont be until next week.

Cheers
Nigel
And a Happy New Year to all

That's correct. What is the voltage if you remove the wire from the alternator ?

By the way, if you changed the split charge diode to a VSR or Victron Argofet you probably wouldn't need an external regulator.

 

[nigel1]

Thanks Paul, so about 5V on D+ is normal.
With the ignition feed wire removed, get 13.6v on the wire terminal, but did not check if any voltage present on the actual D+ terminal.
Will look into VSR option.
Next project is to replace my old Blue Sky mppt controller with Victron mppt, probably have a few more questions then.

 

[PaulRainbow]

Thanks Paul, so about 5V on D+ is normal.

No, i answered the highlighted text, it should be battery voltage.

I'd take the alternator to an auto electrical place that does starters and alternators, get it checked.

With the ignition feed wire removed, get 13.6v on the wire terminal, but did not check if any voltage present on the actual D+ terminal.
Will look into VSR option.
Next project is to replace my old Blue Sky mppt controller with Victron mppt, probably have a few more questions then.

 

[VicS]

No, i answered the highlighted text, it should be battery voltage.

I'd take the alternator to an auto electrical place that does starters and alternators, get it checked.

But Nigel is measuring the voltage on the D+/61 terminal. ie the terminal to which the warning light is connected.

Battery volts will be applied to the warning light but the volts at the alternator terminal will be much lower. I dont know but I would have expected somewhat lower than 5 volts as only the result of the warning light current flowing through the regulator, brushes and and the field coil.

I agree with the suggestion to get the alternator tested