MH40 Autopilot drive motor

[Phantom154]

Where is the drive motor for the autopilot on my MH40? There isn't anything attached at the rudder post, so I guess a radial drive is in one of the steering pedestals. Can I access it from the opening at the top or do I have to climb under the lazarette?

 

[sail sfbay]

Can you remove the aft section cockpit floor? If so, it likely under there.

 

[Phantom154]

Cockpit floor is solid. I’ll take the access panel off the port helm pedestal and see if that works.

 

[jviss]

Cockpit floor is solid. I’ll take the access panel off the port helm pedestal and see if that works.

Well, you'll have a 50/50 chance of finding it in there.

I read somewhere that these used Lewmar steering with direct-drive in the base of the pedestal.

 

[Phantom154]

Yes. The owners manual says it’s a Lewmar Mamba drive.

 

[Phantom154]

Raymarine sent me instructions for checking the autopilot clutch, motor, and course computer. I knew the clutch worked. Putting 12 volts directly to the motor wires showed that it worked as well. Engaging the clutch then applying power to the motor moved the wheel, and changing the polarity moved it in the other direction. Before I checked the outut voltage of the course computer (the next step), i hooked the motor back up and tested by engaging the autopilot and hitting +10 then -10. It worked in both directions. Problem solved, or at least it went away. Maybe just running the motor with a full 13+ volts fixed it. One of the instructions from Raytheon confirmed something I had read in another post here:
"Excessive wear of the electric motor brushes in the autopilot drive unit's motor is the most common cause of this message. When the brushes lose contact with the motor's armature, the motor develops a "dead spot" and will not turn when electricity is applied to it. A temporary fix to the problem is to rap gently but solidly on the chrome ring that surrounds the drive unit with a mallet. This jolt will cause the brushes to move just slightly, and will usually restart the motor."
If the motor had not worked, that would have been my next step, but I didn't have to open the port steering pedestal after all.

 

[jviss]

Can you get new brushes for that motor? Then install them, and use a brush seating stone on the commutator.

 

[Phantom154]

Probably. But I am not sure that was the problem. If it happens again, I will consider that.

 

[Hello Below]

Where is the drive motor for the autopilot on my MH40? There isn't anything attached at the rudder post, so I guess a radial drive is in one of the steering pedestals. Can I access it from the opening at the top or do I have to climb under the lazarette?

Did you ever get an answer for your original question?

 

[Phantom154]

Yes. Port side helm. I could hear it running when I was testing the motor..

 

[artboas]

Yes. Port side helm. I could hear it running when I was testing the motor..

Ok
Few things
The motor is attached to the mamba drive directly.
This is a REALLY expensive motor.
Do not put 12v directly onto the motor.
The autopilot puts out a PWM drive onto the motor, and running it with 12v flat out connected to your steering may over-drive it.
I assume you were running the motor with clutch disengaged when you were testing?
If the motor is not driving, you’ll get an immediate error from the pilot.
When it was “not working” could you hear the motor running at all?
I suspect, if so, that you have a clutch problem, but likely just electrical connections.
Clutches are either good or bad
If the pilot is working now, look for intermittent connections

 

[Phantom154]

No, it was not running at all before but is fine now.