JINMA 204 (2004) Tach wiring ??

[DirtPoor]

As I mentioned in another post, my tach/hour meter is not working on my new Jinma 204.

As suggested, I adjusted the sensor in the flywheel housing and also verified that the sensor would respond (close/open circuit) when I pass a magnet over the face. Connector is ok.

So I pull the instrument cluster. Walla! nothing connected to the terminals on the back of the tach. I pulled the dash harness down enough to verify that there wer no wires or plugs that corresponded to the color and numbers on the flywheel sensor plug.

I was able to identitfy the sensor wires by color and floater (tag) numbers. The black lead is #44 while the blue lead is #36. Now if I can figure out were the sensor lead goes or emerges from the harness.

Before I open the whole wiring harness to trace (hand-over-hand) the tach wires, I would ask if anyone has a circuit diagram of this wiring or if anyone has worked on the tach circuit and knows where the missing tach leads should be connected (or where the tach sensor leads emerg from the harness).

Perhaps someone could look under the dash, from the open hood side and tell me at least what color wires are connected to the tach terminals.

Any help might save me a lot of aggravation and would be appreciated.

I can live without the tach but the hour meter sure would be nice for scheduled maintenance.

Thanks.

Steve

 

[Harrygoodwrench]

Do you have the single tach gauge or the integrated cluster pack? I have the cluster set-up which is most likely different.
wiring diagram below
http://www.tractorconnection.com/drawings-2AB.jpg

 

[DirtPoor]

I have the intragrated cluster, with the tach and hour meter the same component. Long retangular cluster with gages and indiot lights, etc. Different for the schematic you provided. Thanks anyway..

I did some more tracing and found the blue #36 sensor wire in the 9 blade connector at instrument cluster. The black #44 is in another connector (to ground, I think). At the former connector the blue wire color changes to yellow/green wire and goes to a solder pad on the circuit board.

I get good continuity though all connectors and if the tach is internally connected through the printed circuit board, then I must have a bad tach /forums/images/graemlins/frown.gif .

I'll have to see what a new instrument cluster cost. Can't get it under warranty since I purchased it with this known defect with a nominal discount on the tractor price.

Thanks again for the help..


Steve

 

[greg_g]

</font><font color="blue" class="small">( I was able to identitfy the sensor wires by color and floater (tag) numbers. The black lead is #44 while the blue lead is #36. Now if I can figure out were the sensor lead goes or emerges from the harness. )</font>
#44 is always black, and always ground. #36 should be blue where it exits both ends of the harness; down near the bell housing and up under the dash. It should also be marked with the little 36 tag on both ends.

There is a generic wiring diagram at JohnsTractor that might help. But I suspect if you've located/connected both ends without success, you may have to go shopping for a new cluster. But before you commit, consider that the sending unit may be simply lying to the tach.

//greg//

 

[Harrygoodwrench]

I have the same cluster as you describe. Its pouring rain out so I can't go out and do a check of the wiring for you. Don't want to see you buy that cluster and still have trouble. That cluster is pricey!!!!!!!!!!!! Did you make sure yo had a A/C volt signal(engine running of course) from the sensor(permanent magnet generator) that screws into bell housing?

http://www.jinmaparts.com/10Expand.asp?ProductCode=085.046

 

[greg_g]

</font><font color="blue" class="small">( Did you make sure yo had a A/C volt signal(engine running of course) from the sensor(permanent magnet generator) that screws into bell housing? )</font>
I think you probably meant DC Harry, but I don't think there will be any voltage on #36. Pretty sure voltage is supplied at the cluster itself. I believe the sending unit in the bell housing (sensor) is just a magnetic resistor that changes value with RPMs. Wire #36 then transmits these varying resistance values to the cluster, which are then electrically translated into movement as they the amount of voltage fed to the tach.

Having said that, I never actually tested for voltage on that wire. I've always simply assumed that's how it worked.

//greg//

 

[Harrygoodwrench]

Greg,
a permanent magnet generator only produces a analog(A/C) voltage. Its not a very high voltage, maybe 1 to 2 volts I'd say. Its the frequency that changes with increased RPM's. Just like a wheel speed sensor on an ABS equipped car/truck. On more sophisticated systems this analog signal is changed through a signal converter(AC to DC) but with these Jinmas I'm pretty sure the tach is just an analog pulse driven driven unit. Anyways, if a 2 wire generator its A/C, if its a 3 wire chances are its of the Hall effect type(digital signal) and thats a different animal all together. Its AC on these Jinma's please trust me.

Greg, The more I look at your Kama the more I'm impressed!!!!!!!!Sure do wish I had one too. /forums/images/graemlins/wink.gif

 

[DirtPoor]

I figure the sensor is a trigger that is opened and close by a magnet on the flywheel. That is how it works on the Volvo diesel in my sail boat.

The blue wire most likely is switched to ground each time magnetic switch closes as the magnet passes by..

In my tests, the sensor was 'normal open' and then I passed a magnet in front of it, it went to 'closed'. Leading me to believe that the tach needs a pulse negative to count.

It is possible that the magnet is missing from the flywheel. I would have to remove the starter to determine this. (the oil filter mount is in the way to look in the sensor hole).

I put everything back together and I'm on a break now from cutting bush. /forums/images/graemlins/cool.gif

Thanks again,

Steve

 

[greg_g]

</font><font color="blue" class="small">( Its AC on these Jinma's please trust me. )</font>
Bear with me Harry, I'd have to dig out my old BE&E reference texts to follow that. But I called it a magnetic resistor, not a magnetic generator. A magnetic resistor is simply another form of variable resistor, performing a function identical to the coolant temp sending unit (thermistor) and the oil pressure sending unit (pressure rheostat); that is, to influence the amount of voltage that is supplied to the respective display device (gauge/tach).

Having said that, I've never encounted a one wire AC circuit. But just in case we are simply having an acronym problem, I interpret AC to represent alternating current (sine wave) and DC to represent direct current (on/off).

If this tach circuit in fact employs alternating current, what is the AC source, and what represents neutral reference? The battery and alternator only supply DC. Even the wiring diagrams (such as they are) represent the tach and/or hour meter circuit(s) as DC. Or are you implying that the tach sensor itself is an independent AC generator? If so, the neutral reference question is still on the table.

Thanks for the KAMA compliment. Too bad you're not closer. But if you're ever passing thru western KY, stop in for an up-close-and-personal looksee.

//greg//

 

[Harrygoodwrench]

Let me try and explain it this way. There were a couple of guys that had some problems and we determined that it is a permanant magnet design. Its been a while so let me try to remember correctly. A voltmeter was used on both DC and AC scales. DC nothing but a steady low insignifant signal and AC a varying signal. One guy was going to hook up to an oscilliscope but guess never did.
There are 2 ways to use a signal generator (1) is have a wire wound and pass a magnet past the winding, the magnetic lines of flux induce a AC voltage into the windings and a usuable signal is achieved. This type generator is used for applications such as add on cruise control, etc where there is no reluctor ring(tone ring) to provide the breaking of the lines of flux. They just glue/epoxy a small magnet to driveshaft and mount a sensor very close to the magnet. Type (2) this is a sensor of windings wrapped around a small permanant magnet. When the lines of flux are stationary no voltage is induced into the windings. However when the lines of flux are interrupted such as when a piece of ferrous metal passes by the magnet a voltage is induced into the windings. Usually there are notches or cutouts in the flywheel, maybe even the flywheel teeth that do the flux interruption. Have you ever seen a reluctor wheel(tone ring) on a car/truck with ABS? That what interupts the flux and induces the voltage. I do not believe/think Jinma's use a magnet on the flywheel. Others have looked and found none. When I put my 224 crate together my tach didn't work so I did a quick volt check with engine running, had good signal(can't remember what AC volt reading it was and checked a connector, voltage one side nothing other side, repaired connector, all was well) A quick test to see if it is a permanant magnet type is see if a paperclip can be picked up/held with the sensor. To check the winding it should have a specific Ohm reading. I don't know the spec but infinity is definately no good.
I've been a mechanic for over 30 years now, taught college level auto electronics for 8 years and am right now doing adjunct electronics at my college. I'm not trying to brag with qualifications. Electrical and electronics is my forte but I've been wrong before and will be again no doubt. I'm just trying to help as well as others are.