Alternator D+ / 61 Terminal

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nigel1

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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
 
nigel1 said:
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
Click to expand...
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.
 
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.
 
nigel1 said:
Thanks Paul, so about 5V on D+ is normal.
Click to expand...
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.
nigel1 said:
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.
Click to expand...
 
PaulRainbow said:
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.
Click to expand...

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
 
Spent a few days Googling this issue, and that the concensus is that the voltage at D+ with ignition on should be close to battery voltage.
If less, the issue was usually associated with either the alarm/warning light circuit, or the alternator/regulator.

At the boat yesterday. Swapped out the regulator with a new spare, still only 4.7V at the D+ terminal.
Swapped out the alternator with the pervious 60 amp Valeo, and voltage still only 4.7V.

So I am a bit stuck now as to where to further trouble shoot. Would any damage be casued if I fitted a temporary 12V feed direct from the battery to the D+ terminal. I'm thinking that if that produces 12V at the terminal, it would indicate that the voltage drop is between the ignition and the D+ terminal.

Cheers
Nigel
 
No the voltage at the D+/61 terminal will not be close to the battery voltage. It will be battery voltage minus the voltage drop across the warning light.

It seems that 4.7 , or thereabouts , is the reading to expect but make sure all connections in the warning light circuit are good.

Some ( later) VP engines, eg MD2010 etc series B onwards, do have an additional feed from the ignition switch to the D+/61 terminal via a 30ohm resistor. You will see this if you look at at the schematic in the owners manual for an MD2010 B or later.

Try a temporary feed from the ignition switch via a 30 to 50 ohm resistor using a resistor rated at 5 watts minimum. If it cures the problem make it permanent.

You may be able to use pin 3 of the multipin connector if it is wired through rather than additional wiring trailing round the engine compartment.

You have not actually said what the "issues" you are having are.
 
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Hi Vic,
Thanks for responding.
I have spoken to Sterling Power and to the supplier of the alternator (The Starter Motor and Alternator Company), and both have said I should be seeing battery voltage (or close to) at D+ with the ignition on.
The reason I want 12V at D+ is to have enough voltage to excite the alternator.
Alternator ouputs to a split charge diode, and so less than 1V on the B+ terminal. If there is 12V on B+, I know the alternator will start to produce charge.

I want to use the external regulator to get close to the recommended bulk charge for my batteries (6 x Trojan T145). However, as the internal regulator is set to 14.5V, this is the float voltage which will be applied once bulk charge is completed. The external regulator will not reduce voltage below the internal regulators set voltage. I felt this might be a bit excessive if the engine was running for some considerable time.

Sterling suggested using a split charge diode, with the external regulator sense wire connected to the output terminal of the diode (output to the house bank), and the alternator sense wire connected to the input terminal of the diode.
Wired like this, they told me that once the bulk charge had finished, the internal regulator takes over. The input side of the diode will see 14.5V but the ouput will be around 13.8~14V, which is closer to the recommedned float charge of 13.6V

I know there are work arounds to excite the alternator, but I would like to find the cause of the voltage drop at D+

The Sterling External Regulator instructions indicate that it needs 12V input from ignition feed and suggest connecting the igniton feed to the external regulator to the D+ terminal.

Would,be handy if someone here with a TMD22 or MD22 could check the D+ voltage with ignition on but engine stopped.

Cheers
Nigel
 
I asked about this on a Beneteau forum.
Someone with a Volvo Penta D2-55 got back to me and said with battery voltage at 13.5V, there was 11V on the D+ terminal, with igntion on, engine off.

Vic,
I had a look at the MD2010 electrical drawing, and can see the Red/Blue wire connecting to D+ via a resistor.
Looking at the TMD22 manual, can see the Red/Blue wire on the instrument panel going to terminal 3 on the connector, but on the engine side, there is no wire on terminal 3. Assume you meant I can utilise this to connect to D+

Thanks
Nigel
 
nigel1 said:
I asked about this on a Beneteau forum.
Someone with a Volvo Penta D2-55 got back to me and said with battery voltage at 13.5V, there was 11V on the D+ terminal, with igntion on, engine off.
Vic,
I had a look at the MD2010 electrical drawing, and can see the Red/Blue wire connecting to D+ via a resistor.
Looking at the TMD22 manual, can see the Red/Blue wire on the instrument panel going to terminal 3 on the connector, but on the engine side, there is no wire on terminal 3. Assume you meant I can utilise this to connect to D+

Thanks
Nigel
Click to expand...
Yes but only if the wiring loom connects the two terminal 3s together. It may not

I am still puzzled by the high voltages at D+ Suggested and quoted for a D2 . I dont have a wiring diagram for a D2 so cannot comment on that .

The ignition switch puts battery volts on to one terminal of the warning light. The other terminal connects to D+ If the volts at D+ is nearly to equal battery volt there would be only a small voltage difference across the warning light . It is a 12 volt bulb it would not be brightly illuminated.
Because the waring light is brightly illuminated there must be best part of 12volts across it meaning that the volts at D+ must be quite low

FWIW I measured approx. 2 volts at D+ on an old Volvo car
 
The disparity of measured D+ voltage is due to the varying current draw of the measuring meter. You are measuring a voltage on the other side of the indicator lamp from the 12v ignition feed so the resistance of the indicator lamp will also be a factor.
++++ I do hope that the indicator is not an LED without a shunt resistor else the alternator will not excite. ++++
 
Boater Sam said:
The disparity of measured D+ voltage is due to the varying current draw of the measuring meter. You are measuring a voltage on the other side of the indicator lamp from the 12v ignition feed so the resistance of the indicator lamp will also be a factor.
++++ I do hope that the indicator is not an LED without a shunt resistor else the alternator will not excite. ++++
Click to expand...
The current draw of a digital voltmeter is negligible. It will not affect the measurements on a low resistance circuit like the alternator warning light/excitation circuit. Even an old fashioned moving coil multimeter will not significantly affect the readings taken on such a circuit.

Unless the panel, or electronic module, has been swapped for a more modern one the warning light is not an LED.
 
Last edited:
I did no
VicS said:
The current draw of a digital voltmeter is negligible. It will not affect the measurements on a low resistance circuit like the alternator warning light/excitation circuit. Even an old fashioned moving coil multimeter will not significantly affect the readings taken on such a circuit.

Unless the panel, or electronic module, has been swapped for a more modern one the warning light is not an LED.
Click to expand...
I did not quantify the degree of variation, you will note. Any current draw, negligible to significant WILL affect the measured voltage, my comment was correct.
 
Boater Sam said:
I did not quantify the degree of variation, you will note. Any current draw, negligible to significant WILL affect the measured voltage, my comment was correct.
Click to expand...
BS

A digital meter will affect the voltage at D+ by only a few microvolts.
The resolution of a typical multimeter on its 20 volt range is 10 millivolts.
The MEASURED volts at D+ will, therefore, NOT be affected.
 
nigel1 said:
For what its worth, I have tried swapping out the alarm/lamp module with the newer type LED alarm/lamp module, and I get the same voltage reading on the D+ terminal as I do with the incandescent lamp module.

Cheers
Nigel
Click to expand...
That suggests that there may already be a field excitation resistance in place. Maybe a change from what is shown in the manual on later models ????

It would also explain why you get such a high voltage reading on D+.

You have not explained what are the "issues" you are having with the alternator.
 
Vic, the issue is that the alternator does not excite when the engine starts. I can force it to excite either by revving the engine, or by momentarily applying 12V to the B+ terminal. This had not been an issue until I fitted the external regulator which turned out to be defective.

Regarding the resistor in the Red/Blue wire as shown in the electricla drawing for the MD2010, it is described as a "Magnetising resistance (33Ω/9W)"

Is this some sort of special resistor. I am considering adding this to the D+ terminal in the hope that it resolves the issue.

Cheers
Nigel
 
nigel1 said:
Vic, the issue is that the alternator does not excite when the engine starts. I can force it to excite either by revving the engine, or by momentarily applying 12V to the B+ terminal. This had not been an issue until I fitted the external regulator which turned out to be defective.

Regarding the resistor in the Red/Blue wire as shown in the electricla drawing for the MD2010, it is described as a "Magnetising resistance (33Ω/9W)"

Is this some sort of special resistor. I am considering adding this to the D+ terminal in the hope that it resolves the issue.

Cheers
Nigel
Click to expand...

I think you are trying to cure something that does not need to be cured. If the warning light goes out when the engine is revved a little and the battery is charging there is no problem.

"Magnetising resistance" is an interesting name, but reflects what it does i.e. provides current to magnetise the rotor in the alternator before can do so itself
I guess with a 9 watt power rating it will be a wire wound resistor. There will be times when it will produce a bit of heat so needs to be mounted accordingly
 
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