Is my alternator working?

How to check if alternator charging is working

The main alternator charges the house batteries via the DC to DC converter . After the van has been on for ~4 minutes, the auxiliary alternator* will begin charging the batteries via the external Balmar regulator. Read more about the external regulator.

Check Alternator Charging

  • Run your batteries down (lower than 13.2V) and make sure you are not running any heavy loads (air conditioning, etc)
  • Unplug from shore power
  • Turn off the house battery switch
  • Start the engine
  • Monitor the amps on the Victron app or gauge. It should show ~50A (46-50 is fine) within 1 minute of starting the engine. This shows you that the DC-DC converter and stock Mercedes alternator are working properly. If it doesn’t show anything, or shows less than 46-50A, please see below.
  • Continue letting the engine run for at least 4 more minutes. At that point, you should see approximately 150-200A at idle. This shows us that the second alternator is working properly*.

*1st Generation Stage 1 systems do not have a second/auxiliary alternator.


The DC-DC Converter Isn't Working

If the DC-DC converter isn’t working, please see if the screen is on with the engine running. On 1st Gen Revels, it is located here . On 2nd and 3rd Gen Revels, it's located here (labeled solar controller). With the engine on, CH3 on the left side of the screen should be solid. 

If CH3 is on and there's no charging, please submit a support ticket with a video of the DC-DC converter screen.

If CH3 is off or flashing, check the chassis battery voltage using your Victron app (1st Gen Revels, it's the Aux Voltage) or One Place monitor (2nd and 3rd Gen Revels). If the voltage is below 13.2, you have an issue with your stock Mercedes alternator and electrical system preventing the DC-DC converter from turning on. If voltage is ABOVE 13.2, please submit a support ticket.

The Second Alternator Isn't Working

If the second alternator isn’t working, make sure the regulator screen is on with the engine running. The regulator is under the hood. If the regulator screen is off and you have a multimeter, follow this video to check for 12V on the BROWN wire and the RED going into the regulator. If you do not have a multimeter and the screen is off, please submit a support ticket.

If the screen is on and the engine is running, send us a video of the screen from when it says bAL (looks like 6AL) to bAL so that we can check all the data that is displayed. 

Charging Continues After Engine is Off

It is NORMAL for you to see up to 50A of charge for 3-5 minutes after shutting the engine off. Once chassis battery voltage is below 12.8V, the DC-DC converter will shut off. If you have a lithium chassis battery, this time may last longer and can cause the battery to die.