Where to start: non-functioning speedometer 2006 24Ve

[dakota4ce]

With 2 people and a digital ohm meter you go to the green wire on the back of the guage and hook up probe , set guage to read hertz , turn key on and have assitant useing a garden hose blast the paddle wheel and you should see frequency clime from zero go up , if not most likely the paddle wheel assembly is bad.

So I was attempting to conduct this test....apparently I did not?

With the fluke meter set on standard DC voltage, I also failed to repeat the voltage changes I observed with the el cheapo multimeter--ie I failed to repeat the test with the slow rotation with my son. I also read on another thread that the wheel has 2 magnets, which should theoretically show 2 changes per revolution?

All in all, the results are inconclusive and the confusion abounds. I don't have confidence that what I observed was actual the other day. I need to repeat that.

[IDBoating]

So I was attempting to conduct this test....apparently I did not?

That test is based on measuring frequency. Most DMM's don't have a frequency counter feature. That Fluke might - I haven't looked it up - but you would need to be certain you had the meter set properly. As I explained, "DC Hz" is an oxymoron so I'm not sure what that "setting" thinks it's measuring. If you want to do a frequency-based test, you need to be certain the meter is set properly.

With the fluke meter set on standard DC voltage, I also failed to repeat the voltage changes I observed with the el cheapo multimeter--ie I failed to repeat the test with the slow rotation with my son.

So retest with the other meter. Repeat the test EXACTLY. See what results you get.

I also read on another thread that the wheel has 2 magnets, which should theoretically show 2 changes per revolution?

That was my expectation too, as noted earlier, but I'm relying on the fact that you saw ANY change and that it was repeatable as your son rotated the paddlewheel. It could have a single magnet, your son could be reporting his rotations inaccurately... lots of possibilities. Right now, focus on seeing SOME kind of change as the paddlewheel is rotated. Don't worry about pulse counts per revolution yet.

I don't have confidence that what I observed was actual the other day. I need to repeat that.

Exactly. Get back to where you were last time. Use the other meter. Have the same son do the same thing with the paddlewheel. Get your original results back. THEN move one step on your diagnosis.

[dakota4ce]

I contacted Airmar directly, just for fun. They were great, and emailed me the following:

Below are the instructions for testing speed ---


Our sensors are designed to work with various manufacturers products and may accept a supply voltage between 5 V - 12 V.

Keeping this in mind, the output square wave voltage generated when the paddlewheel rotates is equal to the input supply voltage, i.e. if 5 VDC is supplied, a 5 VDC square wave is generated as an output, if 12 VDC is supplied, a 12 VDC square wave is generated.

To test a sensor that has a molded connector using a conventional digital multimeter, perform the following:

NOTE: If the sensor cabling utilizes a molded connector, please reference our on line wiring diagrams to obtain a pin out of the connector. First locate your product in our Cross Reference Guide and obtain the associated wiring diagram reference. then, go to our Wiring Diagrams and download the appropriate diagram. For convenience, it may be easier to perform this test by supplying 12 VDC directly to the sensor from the battery when a molded connector is in place. Using the wiring diagrams to identify the correct pins, insert wires or test pins into the appropriate contacts to supply 12 VDC to the sensor and to take measurements as described below.

To test a sensor that has open wire contacts using a conventional digital multimeter, perform the following:
Connect the speed sensor to the speed display .
Measure across red and shield(ground) on the sensor wiring. this is the dc supply voltage from the display unit which must be between 5 V and 12 V.
Measure across green and shield (ground) on the sensor wiring and spin the paddlewheel. You should read a fluctuating voltage(square wave) between 0 VDC and your measured input supply voltage.
Continue to measure across green and shield and slowly rotate the paddlewheel 1/4 revolution at a time. Each 1/4 turn should generate an on/off status as an output, i.e. 1/4 turn = 0 VDC, next 1/4 turn = supply voltage, next 1/4 turn = 0 VDC, etc.
Results:
--If you fail to obtain a supply voltage from the display unit, there is a fault with the display.
--If you fail to obtain an output signal, the paddlewheel sensor is faulty.

[dakota4ce]

The verdict is in: bad paddlewheel.

Rebuildable, or whole new triducer?

When testing voltage across the green and shield wires, it never changed from 7.4 as the wheel was very slowly rotated. I am pretty confident that I have isololated it.

[ericinmich]

The verdict is in: bad paddlewheel.

Rebuildable, or whole new triducer?

When testing voltage across the green and shield wires, it never changed from 7.4 as the wheel was very slowly rotated. I am pretty confident that I have isololated it.

As long as you are sure the sensor had good power and ground while you were measuring the output wire you are probably correct.

[IDBoating]

When testing voltage across the green and shield wires, it never changed from 7.4 as the wheel was very slowly rotated. I am pretty confident that I have isololated it.

I would interpret that as being a bad SENSOR unit, not a bad paddlewheel. They specifically state that the output voltage should be either zero or the supply (in this case, ~12VDC). You're getting an intermediate value that isn't supposed to occur. That's not the paddlewheel's fault, as it has no control over the output voltage levels - only WHICH level is output at any given time.

[dakota4ce]

I would interpret that as being a bad SENSOR unit, not a bad paddlewheel. They specifically state that the output voltage should be either zero or the supply (in this case, ~12VDC). You're getting an intermediate value that isn't supposed to occur. That's not the paddlewheel's fault, as it has no control over the output voltage levels - only WHICH level is output at any given time.

Exactly. I was wondering if the unit is self contained and not rebuildable or repairable. I stated it too simply, you are absolutely correct. My paddlewheel itself is actually very stable and in great repair, unlike some other modes of failure involving a damaged wheel.

[IDBoating]

Note too that their instructions suggest that you should see two pulses per revolution, just as I had surmised at the beginning. My read of your earlier test says that you saw ONE pulse per rotation. But now, it appears, you are not seeing ANY pulses... just a steady voltage somewhere in the middle. That's not good for a digital system; grey area voltages like that should not happen. Since you reported roughly proper voltages before, I'm wondering if this is an error in the test. For example, a poor ground reference could give you a strange, intermediate voltage like that. Hard to believe that the unit was working well enough to give you pulses before, but now it's failed so completely that it can't even output valid digital voltage levels. My bet is that something else is going on - and interfering with your tests.