Your solenoid is rated at 400Amp so my guess would be 3 amp according to your instruction sheet. If you want to confirm that, just call ScottyB and he can also supply them. I am surprised one was not included in your Alltrax kit. You should be able to test the new controller without the diode for now if you have got all the wiring correct. I do not understand what you mean by removing the ten amp original fuse as that is what supplies and protects power to the low amp circuits. The Big ANN fuse supplies and protects the High amp motor drive circuit.
Remember, when you do get a Diode, the end with the silver band connects to the same terminal on the solenoid as the red/yellow wire or red/white if you still have it connected to red/yellow but i guess you took the red /yellow directly to the solenoid now, and the other end of the diode connects to the same terminal as the red/black wire. If you get it wrong you may destroy the diode.
You can also get your 1N5408 diode from any electronic component suppliers. Amazon for example you could probably buy a pack of ten for little money and crimp your own ring terminal connectors to them. Then you have spares in case you make a mistake LOL
https://www.amazon.com/BOJACK-Rectif...s%2C208&sr=8-4
50 for seven bucks
