Alternator issue

[Little Song]

Hello All.

I have a VP md2020d fitted in my Oceanis 311 Clipper.

Last evening, i inadvertently pressed the on/off engine button while running the engine. From then on the alarm is sounding and battery and tenperature lights are on.

I checked the voltage. When the engine is running voltage rises, but only to about 13.6v while it used to go over 14v.

How can I know if the problem is in the alternator itself or in the voltage regulator? Which is the best way to solve this? To take the alternator out and ask an auto electrician to look at it? Is there anything else that I should look for?

Thanks in advance!

[team karst]

Wild guess is the warning light black box suffered a surge failure and is stuck in “alarm test mode”. That mode usually reached when the preheat toggle is moved to the down position. I believe there is some feature that delays the alarm for a time during cranking.
Yes, an auto el shop will have an alternator test bench. Mine charges $10 for a test, and i have had 2x MD2030 alternators in there.
I have found some odd to me nuances with the imbedded Valeo regulators. For one, they seem to require B+ terminal voltage at startup to operate; meaning they are not fully compatible with diode based isolators. I have had to add a “sneak path”resistor across the isolator to fix that.
Not yet had to dig into the dash electronics, but that day will come. What i do wish is a lockout to keep the starter de-energised when engine is already running.

[Little Song]

Hi team karst.

Thanks for the inputs. Is there any way to de-stuck the “alarm test mode"?...

[team karst]

not sure; try "parts4engines" .com

[Little Song]

The alternator was checked by an electrician. It is working correctly. The problem is with the control unit (VP 873737). I had to order a new one... more than 400 eur...

[team karst]

Originally Posted by Little Song

The alternator was checked by an electrician. It is working correctly. The problem is with the control unit (VP 873737). I had to order a new one... more than 400 eur...

Not bad. only one on ebay, its used for 450.

is the pc board potted or open?