Air Conditioning - Trane gas furnace-A/c combo outside unit

I could use some expert advise. My unit quit working the other night.I called Bro-in-law who's done electrical work on elevators his whole life and ask him how to check fuses in the switch box to see if they are good or not and he had me check them top to bottom then diaginally. He then had me turn off breaker to switch box and pull the bottom of the fuses free and then turn the breaker back on and check them diaganally again. I got a good reading both times diagonal but i
m not sure about individually up and down.Anyway I know I have power into the contactors because if I push in on it to close the contacts my compressor runs. My LED is steady off which says to check mainpower into unit then also four primary causes and one secondary cause which is a low voltage fuse. I always go for a fuse first but I can't seem to locate this one. Anybody know what it might look like and where to find this. I know you'll probly want model #s so i'll respond to replies. Thanks all. Greg.

Trane is notorious for using fusible links & you cannot tell they are bad by looking at them. You have to use an ohm meter to check each one. There should be a wiring diagram on the blower door or somewhere in the furnace to help you find them.

Should look like a small auto fuse. Should find it down on the small control board in the furnace.

ED