I certainly understand your problem. I'am working on the same problem now for about three weeks. I get an error 24 code at times then the display goes blank as soon as I start the engine. I have cleaned all the connection. From what I can tell Ford does not supply any information or help. I have talked to four different dealers. Two of them flat told me a 7740 SLE before 1993 is junk and they would not even work on it. It does not have a data buss it uses a 5VDC loop to pass info back and forth to the Micro processor. There is nobody out there that can repair the processor yet New Holland wants $1061.00 for one with a $400.00 core charge. My question to the dealer is if they can't repair mine why the core charge. I am not giving up on my tractor I have an electronic back ground and I'll find the problem without New Holland.
Roy Ward down in Texas, November 2011