When it comes to testing a diode, you need a special way of testing it. You cannot just look at the diode and say if it is working or not, you have to use an electrical test. I would suggest using a meter reading and using a analog meter to test your diode. Firstly, set your analog meter reader to x1 ohms range in order to check for current diode leakage reverse and also forward testing.

This is how to do a quick spot check on a diode. A diode limits current to only one direction (which means it has polarity - plus and minus in each direction) and I am going to explain how to test that it is working.

The first thing to do is to get your battery and meter and connect one side of the battery indicator to the diode. If you get no reading on the meter for resistance try checking opposite sides of the diode - one way or the other you should get a resistance reading. This means that one way the diode is blocking current (ie infinite resistance) and the other way you should get current going through the diode - this is telling you that the diode is working correctly.

If you were to on the other hand, get a resistance reading on both directions, then this would mean that the diode is shorted out and the diode would be useless. Testing like this can be very useful when trying to pin down a certain problem in a circuit board and can save a lot of time in the long run.