Renze, are you sure it's 11mm ? All the other
zetor bleed screws are 9mm.
Brian
You should be able to release the pressure by moving the lever to drop.
You have to make the decision, do you repair the dynamo if its faulty or do you want to fit an alternator ?
First stage I would do is to check if the dynamo is working.
With the engine running slowly , join the 2 terminals together and see if there is any output, either with a meter or a bulb. if you speed it up and its working you will blow the bulb. if it doesnt work then it may only want polarising: to do this. make sure your battery earth is connected, and run a wire from the other battery terminal and just touch it on to the joined up terminals for a second , again when the engine is running slowly.
There should be output after that if the dynamo is OK, otherwise you'll have to take apart and clean it up and check brushes.
I cant remember if the terminals on the regulator are lettered, maybe Mike can
help on this one, but its really pretty simple to wire up the charging circuit.
Dave