LM317 Always outputting 168mA

I have a LM317 based DDL driver set up with two 1/2 ohm resistors in parallel to set the current to 500mA. Problem is, no matter what resistor(s) I use, the output is always ~160-170mA. Even if I take off all resistors it still outputs at 168mA... which is really weird. I have double and triple checked that I set the circuit up right, including checking the resistors for the correct resistance with my DMM and making sure I have the LM317 pinout correct.

Any ideas what's going on? My only guess is that my LM317 chip is not working correctly and I need a new one, but if anyone has experienced this or has insight into what might be going on, I would love the information.

In case this helps:
Using a test load of 3 1N400X diodes with a 1 ohm resistor.
Powered using 4 AA alkaline batteries. (4x1.5v = 6 v in) (lm317 takes 2.25 + .7 for the reverse polarity protection diode which leaves plenty for the 1.82 forward voltage my the diode.)
Ultimately going to drive a 100mW green module.

Oh no! You have set your driver to work at 5 Amps! It MIGHT be dead. You need 2.5 Ohms to set it to 500mA!

Meatball said:

Oh no! You have set your driver to work at 5 Amps! It MIGHT be dead. You need 2.5 Ohms to set it to 500mA!

Click to expand...

OH NO is right! Thanks for catching that! I forgot about that the mA to Amp conversion. Maybe that will fix things.

awlego said:

In case this helps:
Using a test load of 3 1N400X diodes with a 1 ohm resistor.
Powered using 4 AA alkaline batteries. (4x1.5v = 6 v in) (lm317 takes 2.25 + .7 for the reverse polarity protection diode which leaves plenty for the 1.82 forward voltage my the diode.)
Ultimately going to drive a 100mW green module.

Click to expand...

Dont forget to include Vref =1.25v in your calculation : Vin required = 2.25 + 1.25 + 0.7 = 4.2