How to check Dynamo fitted to old VW Campervan
Many are not aware when checking for power out-put from the old type Bosch Dynamo's (correct name; DC Generator) that were fitted to old VW Campervans the checking procedure is not the same as checking so-called run-of-the-mill standard type dynamo's fitted to other makes of vehicles etc.
Crude way of checking for out-put from a run-of-the-mill Dynamo; Disconnect the two wires connecting to the dynamo's D & F terminals from the vehicle loom. Hot wire & link the D & F terminals together and connect to one side of a 50 or 60 watt'ish bulb, then connect the other side of the bulb to vehicle chassis earth. Start the vehicle engine (not to give to many RPM), bulb should light-up to the point of nealy blowing. There are otherways of checking such as trying to see if the dynamo will motor, or if the vehicle has been stood for many years, the dynamo may just need flashing.
Checking the Bosch type said dynamo's that were fitted to the old VW Campervans; Undertake the same procedure as above, but this time, just connect only the "D" terminal to one side of the said bulb and the other side of the bulb as said, to chassis earth. Lastly, connect the "F" terminal to chassis earth too, then start the vehicle to check as previously stated.
These old Bosch Dynamo's regulate on the negitive side of the field, if their out-put is checked by using the conventional method as used on run-of-the-mill dynamo's, they will show as unservicible (not working) when in fact they maybe OK. Many garage staff have been caught out on this in past years.
Snowy