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Hall effect speedo drive problems

2451 Views 14 Replies 4 Participants Last post by  Jan Zoellner
Just got through installing a GSXR front end on my '03 SV650S. Put my hall effect sensor on per directions on
The speedo works but it's reading about double what it ought to. If I'm doing
roughly 30 mph it reads 60, etc. It also is kind of erratic, will jump from 30 to 17, 40 to 60 mph, etc. I've double checked everything, wiring, magnet polarity, etc.
I don't know what else to check. Anybody got any ideas?? Could it be a faulty sensor? By the way the sensor I'm using is a CH398-ND. Thanks!
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Hi auraaura50
I did this on my 03 sv650s the week before Christmas and found out the following:

1. you are using 8 magnets instead of 4 (03 model uses only 4 magnetic contacts; newer models use 8).

2. the polarity of the magnets. Make sure they are all facing with the same polarity to the hall sensor. If so... flip the polarity of the magnets (i.e.:positive to negative). I believe that on the hall sensor, the sensing area of the device itself has a magnetic charge; the magnets are supposed to repel the sensor.

Your problem sounds more like #2... it happened to me :)
Just my 2 cents.
Does it vary with engine revs? I am having this problem with mine in cold or wet weather currently. My speed when its cold read 168 then jumps til its accurate.

I am using a different sensor though.
DOes that read steel or magnets only I am trying to avoid gluing on magnets right now.
Champ-using 4 magnets. The polarity on all magnets are the same, AND I've reversed them just to check, when reversed it was even worse, speedo was jumping from 5 to 50, etc.
Buzzman-engine rpm doesn't seem to affect the speedo reading
Possible losing read as the wheel spins? causing intermittent reading, if you indeed have a 2003 head unit it should read correctly.

is there a light on the sensor that indicates a field present? if not its time to break out the Multimeter for a read to make sure each magnet is getting picked up.
How close is the sensor to the magnets?
It has to be crazy close to read them just right.

I used these magnets:
Very strong little suckers.

I epoxied them to the little holes in the brake disks (the dimensions of the holes are a little over 9mm diameter and around 6mm deep.
I bought 12 of them and put 3 in each hole interval... way cheaper than getting some kind of spacer/holder.
I made a small hand cut plate (galvanized metal roof shingle; from home depot for about 50 cents) to bolt the sensor (behind the front fender bolts) and bent it from there to put it as close to the magnets a possible.
Thats why avoided his sensor I used these but I am getting a variation in wet or cold weather. And I simply used 3mm Allen heads from Grainger. I have about 2MM sensing distance.

I used an 8MM and I thought I was going to assemble kits but I grew weary of testing and I guess I'll just post this up for the smarter electrical engineers to figure out.
I've got maybe 1/4 inch spacing between the magnets and sensor. How close does it need to be? I could add a washer or 2 and get it closer if necessary......
On the sensor I used.... it specifies 2.03mm max air gap between sensor and magnets.
If you are using it at 1/4 in you have it at 6.35mm.

Your sensor does not have the operating range in its data sheet. I would recommend contacting them for that info.
I'll move it closer and give it a try. Be tomorrow before I can check it though, kinda dark and cold outside now.
OK, I couldn't stand it. Moved the sensor to about 1 mm from magnets. Went for a test ride. It seems even worse! Was reading 30 mph at a crawl in 1st gear. This is messing with my mind. Champ, if I order the sensor you used--how did you wire it??
Never mind Champ. Got it fixed. Since moving the sensor closer to the magnets "speeded up" the speedo, I figured I'd move it farther away. It worked! The magic distance seems to be about 7 mm in case anyone else runs into this problem.
Never mind Champ. Got it fixed. Since moving the sensor closer to the magnets "speeded up" the speedo, I figured I'd move it farther away. It worked! The magic distance seems to be about 7 mm in case anyone else runs into this problem.
It seems the sensor picked up some other metal parts (rotor screws come to mind, depending on where you actually put the magnets). The sensor reacts to magnetizable materials, the magnets work simply as a range extender here.
If it were the screws, your indicated speed should actually have been 2,25 times the real one, which is close enough to double...
On the bike of my wife, we had 1,25 times (5 rotor bolts!) the speed indicated without any magnet installed. :)

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