greggors84
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| posted on 24/5/06 at 04:20 PM |
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Speedo Sensor
My speedo sensor doesnt seem to work. It is the one that senses the magnet passing by. Im guessing it is just a reed switch.
Europa want £30 for one, although im not sure the one i got from them ever worked as the speedo hasnt worked since i fitted it, but i bought the
sensor about 2 years ago now. Is there anywhere that does this sort of sensor cheaper?
In the instructions it says the sensor can be tested by connecting it inline with a light bulb and passing a magent by the sensor, is it as simple as
this? As i have tried it and it doesnt work.
Edited to say i have just found this in Maplins, would it work? Im guessing it will if the sensor is just a simple reed switch and the magnets on my
prop are pretty strong.
http://www.maplin.co.uk/Module.aspx?ModuleNo=4767&criteria=reed%20switch&doy=24m5
[Edited on 24/5/2006 by greggors84]
Chris
The Magnificent 7!
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BenTyreman
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| posted on 24/5/06 at 04:33 PM |
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It probably isn't a reed switch, it's a VR sensor. It's a coil of wire wrapped round a magnetic core, and a small voltage is made
when the magnets pass by it.
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greggors84
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| posted on 24/5/06 at 05:01 PM |
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Thats what i thought it would be at first, but then i read the installation instructions off the CAI website.
This is what they say
quote:
The principle of operation of the sensor is that it generates an electronic pulse each time a magnetic passes the sensor probe, and transmits that
pulse to the electronic speedo.
Which sounds like a VR sensor as you described but...
quote:
Please note that these instructions refer to the magnetic sensor using a reed switch - not to the magnetic proximity sensor
and
quote:
The CAI sensor can easily be tested for quality of signal, without the aid of special meters by connecting one wire to a positive supply and the other
wire to a 12v bulb, which has an earth/ground connection. The bulb should illuminate if the sensor is working properly.
If it was a VR sensor surely it the bulb wouldnt light up. I think what it means in the first quote about sending a pulse is when it switches briefly
letting the current go through as the magnet passes.
[Edited on 24/5/2006 by greggors84]
Chris
The Magnificent 7!
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Kev99
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| posted on 24/5/06 at 07:52 PM |
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Hi
I had this problem it was that I had the pulse settings programmed in the Speedo wrong
to test if your sensor is working properly put a current tester on the two wires and pass the magnet over it u should get a change in the reading if
so it is ok ( cant see a bulb working as it is only a small current produced for a split second)
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greggors84
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| posted on 24/5/06 at 08:46 PM |
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Kev did yours not seem to work at all? Or did it just read wrong? When i turn the ignition on the needle moves up slightly but then doesnt move.
Chris
The Magnificent 7!
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John22000
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| posted on 24/5/06 at 11:26 PM |
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Chris,
Getting my speedo to work was a pain in the ass as well...I thought the whole thing was knackered as well.
Not sure if yours is the same type as the one I have. Mine has a small flat box(sensor) about 8mm X 25mm x 40mm with 3 wires (red,blue and green) and
four magnets in saddles that attach with a metal strap.
I couldn't see any sign of life either freom the speedo or from a test bulb.
I finally found that chassis earths were a major part of the problem + the alignment of the sendor to the magnets( there is a small silver sticker
that needs to be perfectly aligned with the center of the magnet).
Got it working eventually and passed SVA on Monday. Seems to be fairly accurate (indicated 69 MPH at true 70.
Also just for reference I have mine attached to the driveshaft flange, 195X45X15 tyres and have used a pulse calculation of 3150. This is used in
conjunction with a VDO speedo.
Hope this helps,
John.
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Kev99
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| posted on 25/5/06 at 06:40 AM |
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Yes that's what mine did.
What is the pulse setting on the clock if u have got the sender on the prop and two magnets u will need about 6500 pulses this is a good starting
point if on drive shaft as mine is about 1800 pulses.
My clock came programmed at 45000 pulses so u can see why it didn't work
ETB Gauges on 195 / 50 / 15s
[Edited on 25/5/06 by Kev99]
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