B&G Helmstar 740 + Lewmar hydraulic linear drive fault

[Fizzwizz]

Hi All

I've been having a few autohelm issues. I keep getting an error message saying rudder drive failure. The error varies in time to occur, but it seems to happen within seconds now. When the rudder drive fails an inspection of the hydraulic ram reveals the motor is working but the ram just stops moving. A dealer told me "it's stalling out".

What does he mean by this? i.e what happens inside the ram so it doesn't move anymore?
What is the likely culprit?

Is repair cheaper than replacement?

Thanks ... Shaun

Boat. Westerly Oceanmaster 48

 

[Fizzwizz]

Anyone?

 

[claudio]

Are you sure that the motor is still driving the pump ?
If it is and the pump is working correctly, it could be the piston seals.
Do you have any bypass or relief valves in the circuit ?

 

[Fizzwizz]

Hi, thanks for your reply.

The motor definitely runs, it can be heard. There is a valve that is closed when the pilot is engaged, this seems to work as when the rudder drive fails there is always a scramble to disengage it so the helm can be turned manually.

 

[claudio]

Is there a bypass solenoid on the cylinder ?
On some systems the solenoid needs to be energised to provide drive to the ram

 

[Fizzwizz]

There is a solenoid than is constantly energised while the pilot is engaged. I know this gets quite warm.

 

[claudio]

When the solenoid is engaged, can you push the ram piston ?

Edit: Just to add, obvious question, you did check the oil level didn't you ?

 

[Fizzwizz]

No, the steering locks solid, it cannot be turned to move the ram even when the drive fails. It has to be disengaged else we go around in circles.

 

[claudio]

That sounds like your hydraulic circuit is working OK
Does the hydraulic pump motor sound strained, or does it sound ro be spinning freely ?

 

[Fizzwizz]

Just wrote an essay, but it didn't post :-(

The abbreviated version is -
Yes it spins freely (though might sound louder when failing, a little like a pump with no water)
The fluid level is correct

Many thanks ... Shaun

 

[claudio]

Can you check that you actually have hydraulic pressure when the motor is running ?

 

[Fizzwizz]

I'm not sure how I could do that, the pump and ram are a combined unit.

Stood here in the marina the autohelm works fine, but I know after a while at sea it will fail again.

Part of me wonders whether this is truly a ram fault, or whether the electronics are failing - ie the relays which have stuck closed previously. I know the previous owner has used emery paper on the contacts, which removes the coating and predisposes them to oxidation. If the contacts had a lot of resistance this could potentially cause the solenoid to not engage strongly.

I guess the only solution is to try a new ram, if that does the same I need new electronics :-/