When I picked up the cart from my daughter's house I had no golf cart repair knowledge and with no manual and no wiring diagram it seemed overwhelming, but I just kept figuring out the wiring and the systems one by one. It has a type 3 throttle (0-5k Ω). the replacement controller which appears to be new old stock was set to type 1 (5k-0 Ω) and caused a throttle error code along with the missing contactor code. That was easily corrected with the programmer but the missing contactor code never goes away. I keep thinking that there's not that much to it, it shouldn't be this hard. I work on Honda's and Acura's and our saying is "It's never the computer" (of course once every two to three years it is the computer). So I tried to eliminate everything else before sending it off for repair. Then when I got it back and it was the same, I said I knew that it's never the computer. This was followed by double and triple checking everything I had already tested and I decided that they had not actually fixed anything so I sent it off again. Again they told me everything tested good. So I started replacing things that I was sure were good (like the contactor and the wire to pin 17, a perfectly good one foot long copper wire with a good Molex pin on one side and good female spade terminal on the other.) Finally I decided to buy a different controller. Seeing that computer also blink code 3-4 was crushing. But as my friend says "if it was built by man, it can be fixed by man". I wish I knew what signal it is getting that makes it think the contactor is missing.