Lewmar Autopilot Motor

[Harry Brown]

The Autopilot failed on me yesterday.
Upon investigation, it appears that I can hear the motor running when selecting commands but the shaft is not turning. (Motor Part Number Lewmar 8930011)
I am fortunate enough to have a second hand motor that came with the boat when I bought it.
I have swapped the wires over and the motor and shaft turns on this new motor (not fitted to the boat).
So, what can cause the motor to physically not turn the shaft, but I can hear something operating inside?
I would obviously like to fix this to have again as a spare.

Also, would anyone happen to have a manual to show the replacement of the motor please?
Does the motor shaft/Gib Key, need to be in a certain position when installing? I assume the helm wheel needs to be centred, is it just a matter of swapping the drive cog and retention the chains?

Thanks in advance for any advice.

[Yngmar]

So, what can cause the motor to physically not turn the shaft, but I can hear something operating inside?

The actual motor is just a small pancake at the back of my unit, the rest is a gearbox. So if you hear a sound but the output shaft isn't turning, the gears have failed somewhere.

Does the motor shaft/Gib Key, need to be in a certain position when installing? I assume the helm wheel needs to be centred, is it just a matter of swapping the drive cog and retention the chains?

Nothing needs to be centered, the chain should have no slack in it but only be gently tensioned. Then you have to do the Autopilot calibration, which will figure out rudder positions and end stops.

[Yngmar]

So, what can cause the motor to physically not turn the shaft, but I can hear something operating inside?

The actual motor is just a small pancake at the back of my unit, the rest is a gearbox. So if you hear a sound but the output shaft isn't turning, the gears have failed somewhere.

Oh! Almost forgot, there's also the clutch in there, and that's far more likely to have failed than the gears. Possibly just wiring problem (the clutch has a separate pair of wires from the Autopilot processor box).

[Nigel]

...  there's also the clutch in there, and that's far more likely to have failed than the gears. Possibly just wiring problem (the clutch has a separate pair of wires from the Autopilot processor box).

I was going to suggest this, but wasn't sure if it was the same as Raymarine.

[Harry Brown]

Thanks for the replies.

Is the clutch a replaceable item? I'll also check the wiring when I've got it apart.
Here is a picture of the Motor.
Is it the dealer calibration mode I'm carrying out?

[Nigel]

If that "chocolate block" connector is feeding the clutch, I'll wager that is your problem right there.

[Skipperwales]

The clutch is an electromagnet. Mine failed last year, was able, with significant help, to disassemble the unit and identify that the electromagnet had failed. A replacement cost about ?70 compared to well over a thousand for a new unit.

[Harry Brown]

I agree about the choc block, but that is the replacement motor. I'll remove it before installation.
I've removed the broken one and opened it up. the gears appear OK. (Picture below are of gears back in housing and pics of clutch.)
If I put 12v across the clutch terminals, should it move? Does it matter about polarity for the check?

[Harry Brown]

The clutch is an electromagnet. Mine failed last year, was able, with significant help, to disassemble the unit and identify that the electromagnet had failed. A replacement cost about ?70 compared to well over a thousand for a new unit.

Is that ?1000 for the clutch or complete motor?

[Skipperwales]

The complete unit was well over £1000, the electromagnetic clutch was 70. If you put 12 v through the clutch it should activate the magnet. On mine there was a short circuit in the coil.

[Harry Brown]

Would you happen to remember where you got the replacement clutch from?
Google has not been much help this time.
Thanks.

[Nigel]

As you have a spare to compare with, first measure the resistance of the clutch solenoid on both units. Post results.

[Craig]

I am now on my 3rd Lewmar autohelm. ( since boat new in Feb 2010)  All replaced under warranty.

The lewmar autohelm had a problem with the wire that operates the clutch. It wears through. This is why you hear the motor and gears working OK but no engaging of the chain.

The first replacement was couriered to Greece for us. They did not want the failed autohelm back as it wasn't worth fixing. The second failed autohelm we dropped off at their headquarters in Havant ( near Portsmouth, England) and they replaced with a new autohelm. The new autohelm apparently has a fix that stops the clutch from failing. Time will tell.

If Lewmar can't fix the part and merely replace the autohelm, you may be up for a new Autohelm.

I'm not impressed by Lewmar's engineering prowess but I'm greatly impressed by their service.

Craig
"Shirley Valentine"
Gold Coast
Australia

[Harry Brown]

As you have a spare to compare with, first measure the resistance of the clutch solenoid on both units. Post results.

I have left the boat now. I only have the unserviceable one with me. It reads 2 Ohms.

[Harry Brown]

In case anyone is interested whats inside the clutch, here it is.
Basically just potted wire coil. Can't really see how this can fail, but it obviously has!

[Nigel]

I suspect that at 2Ω the coil has shorted somewhere, at 12V that's 6A or nearly 80W.

If you can get the resin out you may be able to wind a new one. This would be a good article for PBO Magazine.

[Salty]

If you can get the resin out you may be able to wind a new one. This would be a good article for PBO Magazine.

Or you could take it to an electric motor rewinding firm and get them to do it for you. I appreciate that this is not specifically an electric motor as such, but having dealt with one of these firms in North Wales several years ago, I found that what they could do was quite amazing, and not expensive, and they would do the whole lot including stripping it down and making a neat job of the repair. In addition by letting them strip it down, they would be able to determine, from what they took out and from any markings on it, things like the wire size and number of windings needed to enable the repaired item to function as required.

[Craig]

Is it the coil that failed?

Lewmar indicated that in both times mine failed, it was the wire going to the coil that failed, not the coil or clutch itself.

Apparently is was a rub point somewhere. I did not open up the autohelm personally as Lewmar replaced the whole autohelm.

Craig
"Shirley Valentine"
Gold Coast
Australia
 

[Harry Brown]

Is it the coil that failed?

Lewmar indicated that in both times mine failed, it was the wire going to the coil that failed, not the coil or clutch itself.

Apparently is was a rub point somewhere. I did not open up the autohelm personally as Lewmar replaced the whole autohelm.

I've replaced the Motor with the spare and it is working fine. So I think it is probably the coil.

[Jackho]

The clutch is an electromagnet. Mine failed last year, was able, with significant help, to disassemble the unit and identify that the electromagnet had failed. A replacement cost about ?70 compared to well over a thousand for a new unit.

Can you advise source of replacement clutch.  I seem to recall when mine failed a replacement clutch was £300.
Being sure it was impossible to "burn out" I removed to find internal connection has come away from the coil.  A bit of digging out of the epoxy got it re soldered. However at 70 euros I would be tempted to buy a spare.

[dawntreader]

When I had issues with my second drive I contacted Cliff Mogridge of Whitlock South and got a very good service. Details attached

[Jackho]

Just a comment about the resistance being 2 ohms.  That might well be correct as this is an electro magnet similar to the windings in an electric motor.

[JohnK]

In case this helps anyone:
I had a similar failure this summer. Autopilot gave up on passage. I disassembled the autopilot motor and found one of the wires going into the clutch had worn and lost connection. Some delicate soldering has got it back up and running.

Part number on clutch was: 3 51 0849 Z001 12V 20W 2706
SG Transmission Type 51 3-51-0849-Z001 12V 20W
They quoted me about 150gbp+vat I think - 4 weeks.

I ended up repairing so cant confirm this part fits 100% (any mods to fit autopilot motor housing) but should be pretty close.

Happy sailing


 

[Nigel]

Just a comment about the resistance being 2 ohms.  That might well be correct as this is an electro magnet similar to the windings in an electric motor.

Perhaps Harry could check the resistance of his working clutch, it does seem very low;  as I said that's 6A.

Coils are strange things, a single shorted turn can make them useless.

[Yngmar]

My (working) clutch coil reads about 50 Ohms, including the short run of cable to the AP box. Having read this thread, I've zip-tied the cable to the motor so it cannot move and break. Thanks for the heads-up