Sorry but i have what is probably a really dumb questions. I am wanting to use a whole bunch of diode in a project i'm working on, the problem is the the only diode i have on hand are the 1n4004. When testing the diode hte resistance one way is O/L on the multimeter which make sense. But when i switch it arround the resistance is 1.5M ohms, which is way to high for the application. I don't get it, i'm using these in kits else where and they seem to be fine.

Why would the resistance be so high? Does it need to be above a certain voltage before it lets anything pass?

Many Thanks

 

Yes. The voltage has to be more than .6 or .7 volts to cross the pn junction.

http://en.wikipedia.org/wiki/Diode

 

Test it with the diode test function of the multimeter. In the reverse direction you will read OL and in forward direction you will read about 600 (this is the voltage drop across the diode).