Diodes can be identified...
by looking to see if there is a "number" printed on them. The number ( if there is one) is on the body of the diode, along with a either a diode symbol, or a band (white, black, red...it needs to contrast with the material that the diode is encased in). For the number to be visible, the diode need to be large enough to actually print the number on the body of the diode. The painted band (or symbol) is used to identify the "cathode" side of the diode, and hence the direction of electron flow.
The diodes of today and quite small, so the "diode designation" my not appear at all on the body of the device. You will just have to trust that whoever sent it to you will have chosen the correct one.
The ones I received from Van's were encased in a heat shrink covering and it had a band marked on one end. That band denoted the cathode side of the diode. Also, Van went a step further in helping...The diode for the Starter Solenoid is encased with Blue heat shrink and the Master / Battery Solenoid is encased in Yellow heat shrink. Both have the band identifying the cathode end. Also, they have ring terminals attached so it is very easy to attach them to the solenoids in the proper orientation.
I also received a diode with the ACS switch. You may want to do a SB search on this item. In this case, ACS is not Aircraft Spruce, but is in fact AirCraft Controls. There is a (rather old) SB out on the older ACS switches...it seems some of the contacts within the switch were getting either burned, or pitted, or welding themselves together...I don't remember which. Anyway, the SB fix was to place a diode across the offending switch points (at the switch) and that helped to supress the arcing within the switch.
But now, we have the diodes across the solenoids, and that also solves the switch problem.
