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Speed sensor stop functioning

3321 Views 11 Replies 8 Participants Last post by  xort

B&G Paddle whell Speed sensor (with 4 years old) just stopped to send data to display with no probable causes. With other speed sensor (borrowed from a store) connected to the Display, values are ok.

So apparently the problem is in the sensor itself. Wheel has the magnetism ok and all the casing seems ok!

Do you have any experience disassembling and trying to fix the speed sensor (after all is like a mini-alternator inside)? B&G replacemente costs a lot of money for and want to try do all I can before spending so much money!

thank you,

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Alfred, it is probably standard design. There's a tiny magnet or two in one or two of the paddle baldes, nothing to go wrong there. And a coil in the base of the impeller. If water has penetrated the coil--it is shot, you don't want to try un-embedding it and rewinding it.

As a "hail mary" you can cut the wire off a few inches above the impeller, see if the defect is in the wire and not the impeller, and is so just replace the wiring run. Sometimes the wire has rotted out from being in the wet, or being stepped on too many times.
....As a "hail mary" you can cut the wire off a few inches above the impeller, see if the defect is in the wire and not the impeller, and is so just replace the wiring run. Sometimes the wire has rotted out from being in the wet, or being stepped on too many times.
Good advice!
Thank you a lot Hellosailor. I will try to open it without breaking the plastic casing. I'm not sure yet if a knife or other toll will be appropriated for that... apparently again the cilinder plastic casing seems a closed "cilinder block"!
Gongui, he didn't mean inside the plastic housing, but the wire it's self a couple of inches from where it comes out of the plastic housing...

Keep in mind that cutting any speed or depth transducer wire and splicing your own to it will void the warrenty of most manufacturers, (being only 4 years old, it is possible to still be covered, I'm not familiar with B&G, but some vendors have a 5 year warrenty...)
before you go any further, is it clean? some times paddle wheels can get growth in as little as a week, which can stop em. i would try to clean it before you cut anything, most of can be removed from inside the boat while in the water as long as you have a plug to put in its place
Scotty, you're 100% correct on the cleaning, Mine just stuck after sitting at the dock for 3 1/2 weeks when I went out for a short sail after work a couple nights ago (been out on friends boats too much recently, not enough time on my own!). After about an hour underway it broke free on it's own and worked fine the rest of the evening.

However, baised on the original post, I don't think that is the problem as he indicated that he's tested the magnents, which implys that he has either pulled the unit out already, or dove under and checked it while still installed.
AIRMAR is one of the largest MFGR's of speed transducers. Check with them before doing surgery. It might be one of theirs and they could be of help to trouble shoot.
Guys, Guys This is a 2 min. check.

First make a continuity check of the wires going to the sender at the plug.

If no continuity, stick straight pins in the wires at the sender as close as you can and check for continuity again.

If you have continuity at the pins than the wire is bad.

If you have continuity all the way to the plug then the sender is ok but the wheel is not spinning.

If you have the sender out you can spin it and you should read pulses at all is well at the connector.

This is best checked with an analog meter because sometimes digital meters will not read pulses.
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Thank you all for your tips.

I did try do remove the paddle wheel steel axis in order to remove it from the plastic housing, to clean and and check the wire, but no way. Using a small screw driver and forcing the axis on one of the sides, did not work. The manual refers a specific wheel position (a more flat paddle way down), but apparently all the four paddles are equal!

The manual also refers to a special tool to remove more easly the axis, delivered with a ... new sensor+cable (200 + Euros) :(

So, I will try to follow Roline and Timebandit suggestions.

Thank you all,

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Alf, there is usually a small bit of iron or a small powerful magnet in one or two of the paddles. You can find out which paddle is "special" by using any conventional magnet, it will attract to that one (or two) special paddle blades. Unless that special bithas fallen out of the blade, in which case you'd see the hole it left, there's not much to be done with the paddle itself. If you can hold it up to your mouth and spin it by blowing on it--it works.
If it doesn't spin, soak it in some Limeaway or CLR or other lime remover and then try a drop of thin oil to lubricate the pin.

What usually happens is that the pickup coil, a coil of wire or a solid-state sensor that is in the housing usually right "above" the paddlewheel, has gotten waterlogged and failed. In this case, all you can do is change the whole impeller/sensor assembly.

SOMETIMES you get lucky, and the problem is that the wire going into the sensor has been crimped, stepped on, or damaged. In that case, you have someone blow on the paddle wheel to simulate it working, while someone else wiggles the wire where it leaves the sensor. Either nothing will show on the display--or the display will suddenly start working. In which case, you can cut and splice in a new wire of similar type. Similarly, if the cable has been damaged ANYWHERE between the display and the impeller--that's all it takes to knock out the whole thing. Crushed? Nicked? Chafed where it runs through a bulkhead?

But in order to confirm that it is the paddle wheel versus the display unit, the best way is still to use an old-fashioned voltmeter with a needle on it. It should show some small voltage and amperage when the impeller is being spun, offhand that could be as little as 1/2 volt at 50 milliamps, AC. It isn't much. You might try to get more specific numbers from the maker.
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I read recently somewhere that the paddlewheels had a lifecycle and it does fail and needs replacing. Not sure why, but mine spins freely but does not work. I'll check the continuity first.
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