General Info: Volvo Penta MDI Black Box RECALL

[epletan]

Originally Posted by Kasanti

Why didn't you select a voltage regulator for the input to the "black box" of appropriate specificatations? Just asking, no criticism.

You are right, in fact it was my first idea.
I bought a voltage regulator Magic 12V/12V-20A from Mastervolt and I installed it (300€). It was very disapoint because the engine has never want to start (in the MDI box, the fusible is 15A).
After this bad experience I tried the diode (some €uros) and for the price the result is most efficient.
I think that the voltage regulator cut voltage peaks and so prevent the start of the engine. The diode is a very "simple" composant which permit of the peaks (current and/or voltage) to pass.
Recently I tried to put 2 diodes in serial in order to have 1.4V of voltage drop but the result has been to prevent the engine to start.
If you have read my post on August 2020, I explained that I used 2 diodes in parallel of a bridge of diodes (because it's was the alone composant that I had under the hand). It was perfect during two seasons but the last summer during last day of my holidays one the two diode broke meaning that the diode is put it in short cut. In that case the other diode is short cut by the diode broken and it's as you have nothing. I think that the diodes of the bridge was too just and I had been run my engine to high at the start (many (too?) current provided by the alternator => the diode breaks). The old problems (alarms and so on) came back.
It's why, I have changed my bridge of diode with a power diode VS-70HF (70A/120V). I think that the result will be more stable and more resistant when the engine run at high level.
I found on internet 10 diodes (5 VS-70HF and VS-70HFR for 13€).
https://www.amazon.fr/gp/product/B08...?ie=UTF8&psc=1
Best regards
epletan

[silvercreek]

Very clever solution epletan.

One question – have you hooked up the brown voltage sense wire from the MDI box to anything?

I too have an externally regulatored alternator and am getting the charging errors from the Volvo panel intermittently. I tracked it down to triggering whenever the MDI voltage exceeds 14V.

I did not hook up the brown voltage sense wire, and I believe the MDI sees 0V there, and 14+V on the MDI, and triggers an alarm. But if they both matched, I think it would not alarm. This is actually how a stock configuration works, and it too can rise above 14V but doesn't alarm.

Of course, in order for this to work, your alternator needs a D+ terminal, which mine doesn't have since I converted it to P-type, which in retrospect was a mistake. I am evaluating options to restore the D+ terminal so that I can hook the brown wire up to it, which I hypothesize will eliminate the alarms.

[silvercreek]

Originally Posted by silvercreek

Very clever solution epletan.

One question – have you hooked up the brown voltage sense wire from the MDI box to anything?

I too have an externally regulatored alternator and am getting the charging errors from the Volvo panel intermittently. I tracked it down to triggering whenever the MDI voltage exceeds 14V.

I did not hook up the brown voltage sense wire, and I believe the MDI sees 0V there, and 14+V on the MDI, and triggers an alarm. But if they both matched, I think it would not alarm. This is actually how a stock configuration works, and it too can rise above 14V but doesn't alarm.

Of course, in order for this to work, your alternator needs a D+ terminal, which mine doesn't have since I converted it to P-type, which in retrospect was a mistake. I am evaluating options to restore the D+ terminal so that I can hook the brown wire up to it, which I hypothesize will eliminate the alarms.

I would like to clarify my comment above.

The brown wire is really best referred to as the lamp/warning wire, not voltage sense. The MDI uses this wire to monitor the alternator operation. As long as 12v is applied to this, the MDI should not alarm. If no voltage is applied, but the MDI power supply rises above +14v, it will alarm.

So one can prevent alarms by either applying 12v to the brown wire (but only while the engine is running; otherwise it will prevent the MDI from turning off by effectively supplying it with power) or by connecting it to the D+ terminal of your alternator, which does the same thing.

[epletan]

Hello silvercreek,
I have provided drawing and explanations in my post#5 (14-08-2020), post#13 (28-03-2022) and post#16 (034-04-2022) but the most important is post#7 (10-01-2020).
You have all my story but if you cannot download the pdf files then, tell me and I can send you the files.
If you have the "Wiring Alt-Volvo-1.pdf" file, you can see that I have wired the brown wire of the MDI box (7) to the B+ of the alternator (via the battery isolator). This wire is piloted by the relay R2 and I have 14.7V when the motor run and 0V when it is stopped.
I have no problem to have 14.7V on the pin 7 of the MDI box. For me, the problem is to have more than 13.8V on the B+ pin of the MDI box (it's for that I inserted a diode before B+ pin in order to drop the voltage to have about 14V on B+ and not 14.7V).

[silvercreek]

Originally Posted by epletan

Hello silvercreek,
I have provided drawing and explanations in my post#5 (14-08-2020), post#13 (28-03-2022) and post#16 (034-04-2022) but the most important is post#7 (10-01-2020).
You have all my story but if you cannot download the pdf files then, tell me and I can send you the files.
If you have the "Wiring Alt-Volvo-1.pdf" file, you can see that I have wired the brown wire of the MDI box (7) to the B+ of the alternator (via the battery isolator). This wire is piloted by the relay R2 and I have 14.7V when the motor run and 0V when it is stopped.
I have no problem to have 14.7V on the pin 7 of the MDI box. For me, the problem is to have more than 13.8V on the B+ pin of the MDI box (it's for that I inserted a diode before B+ pin in order to drop the voltage to have about 14V on B+ and not 14.7V).

Thanks for pointing this out, I had missed it when first reviewing your posts.

I do see you have the brown wire hooked to a switched 12V source, which should work to silence the alarms. It's curious that it doesn't because even the stock configuration from the factory charges to 14.2V, and yet does not result in an alarm (see the Mitsubishi alternator specs attached).

There must be another piece of the puzzle we are missing here which is causing these alarms for us.

Note I'm not suggesting your diode approach doesn't work (clearly it does) or that it's not a good solution (it is). I just believe that there is another root cause at play that might make a diode unnecessary, if we can find it.

I am starting to suspect that the brown wire (pin 7) must be connected to D+ of the alternator, and not simply a switched nominal 12V supply, in order to work. In a stock alternator the D+ is a partially-rectified DC voltage coming from the diode trio which has pulses. It is conceivable that the MDI is counting these pulses to confirm alternator operation. A switched nominal 12V supply would be smooth and lack the pulses, potentially triggering the MDI to alarm. Hmm...

[epletan]

Thank you silvercreek for the Mitsubishi alternator specs. I searched this kind of document without succes and it's very interesting to analyze it.
May be you are right and we have not all the pieces of the puzzle but it's also possible that the MDI box is simply a bad conception from Volvo. Don't accept more than 13.8V is very problematic and accept only Volvo equipement is very restricted.
Please, consult post #3 (09-02-2019), it's very relevant and for me it had been the start point to the solution with the diode.
The best solution would be that Volvo develop a new MDI box with technical specifications better (principles, max level voltage > 13,8V ie between 14.5V and 15,0V (condition mandatory to have full charge on the batteries), better components regarding the hot temperature, third party equipments and so on).
While waiting for this improbable solution, the diode is the best workaround for my point of view.