GL1200 Speed Sensor failures & repair


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SlowTyper
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GL1200 Speed Sensor failures & repair

Postby SlowTyper » Sun Jul 26, 2015 12:26 am



The short version of this post: If you are willing to make the effort, a failed GL1200A speed sensor is likely repairable using a generic Hall Effect IC (I used a SS451A, with the addition of a 6.8K pull-up resistor).

The full disclosure: I have dealt with three GL1200A speed sensor failures. (Note, others have experienced geardrive failures; mine have all been electrical issues.) My third time around I learned more about GL1200 speed sensors than I ever wanted to know! My saga follows…

My first speed sensor failure was merely a broken wire near the sensor itself on my ’85 Aspencade. The rubber boot had cracked, letting in corrosive water and allowing the wiring harness to bend back & forth until a wire broke in two. I was able to fix it simply by opening the unit and soldering the wiring harness back onto the remaining wire stubs coming off the circuit board. I then coated it with RTV to waterproof it and provide some strain relief.

My second speed sensor failure experience was again on my ’85 Aspencade. This time it was in the circuitry of the sensor. Specifically, the Hall Effect component that counts the rotations of a round magnet had shorted out. I determined this by carefully digging out the potting material (which reduces vibration damage), tracing the schematic, and then doing a bit of troubleshooting on my workbench. Once I realized that the Hall Effect IC had failed and that an exact replacement was no longer available, I opened my wallet wide and paid an exorbitant price for the only used GL1200 sensor I could find on the Internet at that time.

Here’s my hand scribbled sketch of that circuit schematic:

My third experience with a speed sensor failure occurred when my neighbor came knocking on my door informing me that the speedometer, auto-volume control, odometer, turn signal cancel, and cruise control had all suddenly quit working on his ’87 Aspencade. I informed him that a failed speed sensor would explain all of those symptoms. He was a bit surprised that one part could cause all those things to quit, but I assured him that was the case.

Based on my experience with my earlier speed sensor failures, I first checked the voltages at his speed sensor. He also found a diagnostic routine in his service manual that indicated that the voltage between the Blk/Brn wire and the Blu/Yel wire should toggle between 0 and 5 volts as the front wheel was rotated. Thus, it surprised me to measure 10 volts on the Blk/Brn power lead rather than the 5 volts I had measured earlier on my own ’85 and also indicated in his shop manual. Thus, I [erroneously] concluded that the LCD cluster must have had its 5 volt power circuitry short out. So we swapped out his LCD display with a spare I had purchased long ago on eBay. But his speedometer still did not work. And to my surprise, my spare LCD panel also put out 10 volts!

I then did a bit of Internet searching and discovered that Honda changed the part numbers for the speed sensor several times during the four GL1200 model years. I also noticed that the gender of the connector for his speed sensor was opposite of mine. Could it be that Honda upped the voltage in ’87 to accommodate the cruise control option? Hmmm… I suspect that is in fact the case, although it does not appear to be well documented.

Subsequently, I focused on his speed sensor sending unit itself. After carefully prying out the potting material, I traced the schematic. Here are my notations:

It turns out the circuitry is quite similar to the one on my ‘85, except for the addition of a FET buffer stage. So, clearly, a modification had been made in ’87 to accommodate the speed signal needed by the cruise control. (Other than having a different connector, I see no reason why this ’87 version would not also work on older GL1200’s. Once repaired, it worked on my bench over a voltage range of 4-16VDC.)

After a bit of troubleshooting, I determined the Hall Effect IC had also failed on his sensor. However, my neighbor was not at all anxious to shell out big $$ to get a replacement sensor. Furthermore, if the ’87 in fact used a version different from previous year’s speed sensors, it would make finding an affordable compatible replacement even less likely.

**OK. Time out! I hear someone asking at this point: “How do I test my Speed Sensor?” Well, the Green wire is ground. Depending on the year, there should be 5 or 10VDC on the Blk/Brn wire. Then, as you rotate the tire (or turn the shaft in the sensor with a small screwdriver) the voltage on the Blu/Yel wire should toggle between ground and 5-10VDC. These DC voltages should be tested with a meter rather than a test light, since there is not enough current available to run a test light. The sensor harness plugs in under the front left edge of the false fuel tank, and it is easiest to poke meter test leads into this connector for testing purposes.

So… Back to the narrative: I wondered if the Hall Effect IC could be replaced with a generic version. I went shopping on Amazon and discovered I could get 10 generic Hall Effect ICs delivered overnight for a mere $10. I took a chance and clicked “Buy.”

When I got the Hall Effect ICs, I began a bit of bench experimentation. I determined that the Hall Effect chip sensed magnetism both above and below it. Thus I had to tip it on edge so the top or bottom faced the magnet, rather than mounting it flat on the circuit board. And since these Hall Effect ICs had open collector outputs (most do), I added a pull up resistor (6.8K) to its output to make it work.

But to our dismay, the repair project failed the road test – the displayed speed was half of the bike’s actual speed! So I did a bit more Internet searching. I discovered Hall Effect ICs come in three versions: unipolar, bipolar, and omnipolar. These versions respond to North & South magnetic fields differently. The version I bought (bipolar), turns on when subjected to South from the top and North from the bottom. In this design, alternating magnetic fields insure definite ON/OFF states (see http://www.allegromicro.com/en/Design-Center/Technical-Documents/Hall-Effect-Sensor-IC-Publications/Bipolar-Switch-Hall-Effect-ICs.aspx for an explanation). But in the design of the GL1200 speed sensor, an output pulse should occur for both South and North fields, resulting in eight pulses per complete rotation of the magnet. The bipolar Hall Effect IC I used reacted only to the South pole, and therefore was only putting out four pulses per full rotation of the magnet, and not the required eight.

As a workaround, I tried gluing two ICs back-to-back (one for South and one for North). However, it was difficult to keep all the leads from shorting out in such a crowded space. Furthermore, the one furthest from the magnet did not want to work reliably. So I then tried mounting the ICs 90 degrees apart (either side of the original location), with one upside down so that it would respond to the opposite magnetic polarity. However, I was unable to tweak the mounting locations such that a symmetrical output resulted. As a result, inconsistent speed indications caused it to again flunk our road test.

So I ordered an ‘Omnipolar’ Hall Effect IC. That worked! On the bench and on the street. Yeah!

As a side note, while I was waiting for the new ICs to arrive, I attempted another mounting variation of my bipolar ICs. I read that the Hall Effect circuitry was in the top of the IC. So I glued two ICs together top-to-top, with the leads coming out opposite ends so they would be less apt to short out against each other. This arrangement meant that the magnetic sensing area of the IC located furthest away from the magnet would be closer than when the ICs were attached to each other on the bottom side. This workaround resulted in an output that looked good on my bench oscilloscope. However, since I had ordered some omnipolar Hall Effect ICs, and they were better suited for this application, I did not bother epoxying this hack together for a road test – thus, I cannot assure you if it will work reliably.

Note that because the mounting angle for the replacement Hall Effect IC ended up being on edge, I epoxied the part in place. Time will tell how reliable this mounting scheme will be, but I see no reason why it would not hold up reasonably well. I also potted the circuit board again to make it durable.

So, the bottom line is that it is quite likely that your failed speed sensor can be repaired with a $2 part and the addition of a $0.10 resistor, along with a generous dose of epoxy and a bit of your time.



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Re: GL1200 Speed Sensor failures & repair

Postby virgilmobile » Sun Jul 26, 2015 2:54 pm

I like the details..very nice job...
Could this be a side line for you.?
Get a couple of broken ones,fix them and do a exchange program...
Something like...send me your broken one and I'll send you a rebuilt for X dollars....

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SlowTyper
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Re: GL1200 Speed Sensor failures & repair

Postby SlowTyper » Sun Jul 26, 2015 8:12 pm

VirgilMobile, I am self employed (Lors Consulting, LLC), so do electronic repair for a living. When shipping the item is practical, some of my business does come from outside the Pierre, SD area.

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Re: GL1200 Speed Sensor failures & repair

Postby MacNoob » Sun Nov 01, 2015 10:51 am

Interesting repair! My '85 Aspencade speed sensor failed recently - but it was the ears on the plastic gear in the front wheel gearbox that broke.

Have you had any queries since your post regarding performing more of these electronic module repairs? I wonder what causes the Hall Effect sensor failure?

kc8sil
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Re: GL1200 Speed Sensor failures & repair

Postby kc8sil » Mon Nov 02, 2015 9:30 am

I was able to revive the speed sensor on my "84 Aspencade by spraying electrical contact cleaner into it while holding it upside down/ hole facing floor. Quite a bit of rust colored cleaner liquid came out and I continued spraying until it ran clear.

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SlowTyper
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Re: GL1200 Speed Sensor failures & repair

Postby SlowTyper » Mon Nov 02, 2015 12:10 pm

MacNoob,

I have no any idea what causes the Hall Effect chip to fail. Obviously, it is exposed to a lot of vibration and G forces being mounted to the front tire. Mine happened to fail not long after going airborne with the bike (showing off; the progressive shocks prevented the bike from bottoming out).
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MacNoob
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Re: GL1200 Speed Sensor failures & repair

Postby MacNoob » Mon Nov 02, 2015 6:54 pm

Well that's not something you see every day.

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Re: GL1200 Speed Sensor failures & repair

Postby extjason » Wed Jun 01, 2016 3:39 am

I would just like to say thank you very much for this really helpful info!!!
Not only have I solved the problem, but have learned all about these Omni polar, bipolar,,,hall sensors and why are they used for.

At first, the gear failed on my GL 1200A, after I purchased a new one the speed sensor malfunctioned, so I was a bit out of luck. We all know about how it is getting a replacement.

With a Garmin navigation I tried to exchange the whole speed showing issue, but that is not the real thing. I have been looking at this post for a couple of months now and decided to try installing the hall sensor myself, it works perfectly- thanks again!!!

A big smile came to my face while testing it yesterday, when I saw the 1KM/h on the screen that I have not seen in a long time, I knew this is going. Actually the speed sensor is very easy to "snap in and out" to test, clean, etc.

Today I will be filling it up with epoxy.

Sometimes repairs such as these are a challenge, but at the same time fun!

Here is how my repair looks like.


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SlowTyper
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Re: GL1200 Speed Sensor failures & repair

Postby SlowTyper » Wed Jun 01, 2016 2:21 pm

extjason wrote:Here is how my repair looks like.


Glad to hear you were helped by the post...

I am also glad to see that you posted a picture of your repair. I am sure it will help others to see exactly how the repair should look, just prior to filling the thing back up with epoxy.

I should probably caution others that I discovered that you do not want to mount the Hall Effect IC too close to the spinning magnet. I would think that the closer the better, but in practice, being too close resulted in erratic speed indications at higher speeds on the unit I repaired. I think being flush with edge of the circuit board is about as close as you should try to get. On the other hand, mounting it back from the edge of the circuit board is also a problem in that you will not get any signal.

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Re: GL1200 Speed Sensor failures & repair

Postby Rusty Bike » Thu Jun 02, 2016 7:12 pm

extjason, Not trying to be a **** here but I would suggest your repair may fail due to poor solder joints. Do some research on proper soldering technique and familiarize yourself with what a good solder joint looks like. Afterwards, get some wire and practice your soldering skills. It would be a shame to have to redo that job after sealing it with epoxy. Good luck...

SlowTyper, thank you for your expertise and effort both on the repair and your willingness to share your findings...Rusty

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Re: GL1200 Speed Sensor failures & repair

Postby WingAdmin » Thu Jun 02, 2016 11:02 pm

Rusty Bike wrote:extjason, Not trying to be a **** here but I would suggest your repair may fail due to poor solder joints. Do some research on proper soldering technique and familiarize yourself with what a good solder joint looks like. Afterwards, get some wire and practice your soldering skills. It would be a shame to have to redo that job after sealing it with epoxy. Good luck...

SlowTyper, thank you for your expertise and effort both on the repair and your willingness to share your findings...Rusty


I have to agree, the quality of the soldering, particularly those cold solder joints on the resistor, is poor - and you can pretty much expect that it is going to oxidize and fail at some point. I'd also suggest that perhaps your soldering iron/implement was not hot enough for the solder you were using.

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Re: GL1200 Speed Sensor failures & repair

Postby extjason » Fri Jun 03, 2016 2:22 am

Thanks all for the comments.

I could have sent a photo of the board on the underside, there the solder joints are perfectly made. The resistor will hold, it is very narrow to solder between the points and tricky to do. If I had done the procedure again I had widened the 2 outer holes and added the resistor direct to them.

Concerning the distance to the magnetic wheel I used 1mm of space. The epoxy not only serves as moisture protection, but to make the sensor stick firmly as it is only "laying" on the board.

Been riding these days now, everything working perfectly! I have also used a gasket sealer around the top of the sensor housing; as you can see the old gasket is damaged and I dont want any moisture getting in there.

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Re: GL1200 Speed Sensor failures & repair

Postby NITROBANDIT » Mon Jul 04, 2016 7:52 pm

What OHM resistor did you use along with the omnipolar hall effect switch, and did you also pull the white plastic cover off from the back of the board? Also, what type or brand of epoxy do you use to repot the board?

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Re: GL1200 Speed Sensor failures & repair

Postby SlowTyper » Tue Jul 05, 2016 12:09 am

NITROBANDIT wrote:What OHM resistor did you use along with the omnipolar hall effect switch, and did you also pull the white plastic cover off from the back of the board? Also, what type or brand of epoxy do you use to repot the board?


Yes, you will need to pull the white plastic cover off in order to solder to the circuit board. I used clear silicon to repot the board because I wanted something that could be removed later if need be. (Buried in the original post is the value of the pull-up resistor I used: 6.8K.)

I have repaired another one since my original post. This time I mounted the Hall Effect Transistor upside-down, so that during assembly I could glue it to the circuit board (nearly flush with the edge of the circuit board) using a drop of super glue. This held the part in place when I filled the thing with silicon sealant later. And yes, I made sure the wires were bent low enough to not short out against the metal cover.




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