Well, "many of these boards" doesn't necessarily mean that your specific one is included. If the original diode is physically much smaller, and with smaller leads, then it's most likely a smaller current one (1A OR 2A). You could try 1N4007/RL207, or contacting Daikin directly and see if they can assist you. And no, there's absolutely no diode called 0203 (it's either custom made, or poorly labelled) Also, I think you might be a bit too naive here. You seem to think that replacing that one diode would fix things (which may or may not be the case) because there's a strong possibility that there are additional components that have also gone bad! My advice, try what I mentioned^, no go, then tell your friend to order a replacement board and get it done with (he could also pay extra for premium/expiedited shipping, if he needs it urgently) Testing the other components can be quite time consuming, you may or may not have the equipment required to do so, and given the fact you're doing him a favor, I don't think it's really worth your time.