711c install for 12v reversible drive problem

[georgeb22]

Previous install was Furuno NAVpilot 511 and all was well until control heads screens fogged.
Installed in Grand Banks 42 with cable steering and using original Benmar autopilot drive motor, 12 volt reversible with clutch.
At the rudder test the 10 amp breaker opens before the wheel turns. The diagnostic says drive unit unknown and Bypass/Clutch not present. Doing the Air Bleeding routine to identify the drive unit also trips the breaker. Both control head units are properly terminated. The same wires used in the previous installation are being used. Two wires for the motor on TB-2 and the two for the clutch on TB-3. Same breaker also.
Since the rudder unit test "automatically detects the drive unit" but aborts on tripping the breaker I am stuck and need help as to how to troubleshoot.

 

[georgeb22]

Update: I think the Benmar 14B is the culprit. It is pulling 20 amps (DC Ammeter reading) when actuated and the 10 amp breaker is doing it's job. I'll pursue this and post the results. I find it hard to get much info on the ancient Benmar motor drive and welcome any suggestions.

 

[Johnny Electron]

If the Navpilot 500 worked, then the 711C will as long as the connected items are good. The input power to the pilot is normally breaker'ed for about 30 amps on the 500 series and about 25 amps on the 700 series. This is to account for the turn on power surge. The 711C has larger inductors so the turn on current isn't as large. Solenoids are not like pumps and they don't pull a lot of current. It sounds like a shorted solenoid or wiring not connected correctly resulting in a short when the pilot goes to send out the drive signal. Also note that whatever power you put into the pilot you get out. So if the 500 was working off 12v and you changed to 24v with the 711c, you have also changed the voltage going out to the solenoid system. These are just a few thoughts I had reading your post.

 

[georgeb22]

Thank You for following up.
Benmar recommended a test without the 711C as I was planning to do also. So the same 10 A breaker will power the Benmar motor drive: the field winding's are powered, then the clutch solenoid, then the motor. Start up is smooth operating the entire chain, cables and thus rudders.
Questions:
1. why should I have to go to a larger breaker if as stated the "turn on current isn't as large?
2. Why does it not recognize the clutch solenoid, really a relay with 77 ohm coil resistance?
3. The wiring is pretty simple and I've checked it, but what could be mis-wired to cause this?

 

[georgeb22]

Changed to 20 Amp breaker and it completed the installation. Makes no sense but..............DONE

 

[Johnny Electron]

Wow that's great. I guess it was starving for current at turn on of the pump. I had just talked to one of the engineers about your case and had some things to try. You just saved me a ton of typing. lol :jump