First, check the voltage at the 24 volt bus near the course computer. Assuming that you have good voltage at that point, I can almost guaranty that the following will work.

Next, buy some CorrosionX. Place a very small amount in a small container. Using a small brush, coat all of the wire contact points where a wire, connector, or a clip joins either the course computer, the drive, and the control head. If a Raymarine Seatalk connector is used at the control head, remove it and coat the pins and the inside of the receptacle.

This stuff is amazing. I have used it on wiring connections, computers, everything. It is a private company that produces CorrosionX for Aviation and Marine solutions. http://www.corrosionx.com/ It is not flammable. If you have to ship it via air, buy the trigger bottle, because the aerosol will be considered dangerous.

I do not have any connection with this company...if it were a public company, I would buy stock!

Let me know if it works for you...so far I am batting 1000 in situations like you described.

Best,

Bill
s/v BeBe, SM2k, #387
Currently Malaysia