JINMA 204 (2004) Tach wiring ??

   / JINMA 204 (2004) Tach wiring ?? #11  
Greg, you posted while I was posting LOL. Wife went down to beautiful Tennesse to visit parents. Wish I could go but work wouldn't allow it. Suure would like to try that Kama out!!!!!!!Getting back to this electrical problem. These cluster gauge sets can be confusing. I have the same cluster set-up, wish I had the individual guages. Putting all the eggs in one basket so to speak. We'll I "think" the tach/hour meter is a separate circuit driven by the sensor in the bellhousing. I believe the rest of the gauges, etc are all separate DC circuits.
I know I had that bad connector and checked it with my digital meter. It was AC. I'm getting older but not totally senile yet(maybe wife would disagree with that). I just do this stuff so fast out of instinct and do the fix.
I think it was Paul Wilkie, or DIY guy that had problem. We went thru this on the old, old old, board. or was it 5 old boards ago?
When I AC I'm talking a 2 wire signal generator which is a low voltage here. Its a alternating current. High/low switching from positive to negative. Many older equipment used ac type drive tachs, etc. real old technology. Good grief(old age) I still remember the specs for GM products for the distributor pick-up coil. (500 to 1500 Ohms resistance, must be able to put out 1 volt AC) It was not the voltage but the frequency of the cycles. Of course it was changed to a DC voltage thru a DC signal converter inside the ignition module.
I think we are both really saying the same thing but termonology/semantics gets in the way. True, AC is high/low, but the frequency of high/low is directly proportional to its output. Digital is a more on/off signal. In order for a AC signal to be used "accurately" the signal must be cleaned/ clipped/ changed to a more true on/off 0/1 so it can be used in a digital binary system. We are talking old old tech on these China systems so this isn't a factor yet,,,,,,,,,until the tree huggers want computers on our tractors. Don't laugh,,, its gonna come one day.
I always like conversing with Greg,,,, one hellava nice, knowegable guy and always willing to help others.
 
   / JINMA 204 (2004) Tach wiring ?? #12  
Well both you guys are to technical for me! The tach sensor does have a permanent magnet (unless you screw it into the ring gear teeth, then it is not so permanent!. The teeth are the trigger, there is no magnet, if you look the tip of the sensor is directly in line with the ring gear teeth. So weather it is AC or pulsed DC, there is a signal voltage generated that varies with the speed of the ring gear teeth going past the magnet. Hope that is Dirtpoor's problem as it is the easy and most economical fix.
 
   / JINMA 204 (2004) Tach wiring ??
  • Thread Starter
#13  
Ok. There is voltage on the sensor leads. It's AC and with the leads disconnected from the instrument cluster I read 2.8 VAC with engine at idle and it only increase to 2.91 when rev'ed up to a moderate (~1200 rpm) spd.

With sensor harness plugged into the cluster the reading drop slightly to 2.18 VAC and there is no significant increase when the engine is rev'ed up.

This would lead me to assume the tach is using the pulse freq to indicate RPM rather that the voltage output of the sensor.

It appears that my problem most likely is in the tach since the sensor is providing a signal.

Steve
 
   / JINMA 204 (2004) Tach wiring ?? #14  
Kinda sounds like you you have it narrowed down. I remember when I put my 224 together last fall. No tach, did a quick ac volt check engine running, think its was in 1.5 volt range but it was a while ago., no voltage one side of connector, voltage on other, repaired terminals, problem resolved.
Too bad its the "expensive" piece. I don't think the cluster is serviceable, only by complete replacement. I did find a Ohm reading today from Johnstractor, it was about 510-530 or so Ohms for the sensor in the trans housing, but that only checks the windings not what it puts out. I would suggest doing some shopping as these clusters are pricey$$ as I'm sure you know.
 
   / JINMA 204 (2004) Tach wiring ??
  • Thread Starter
#15  
Pricey is right!

I just checked jinmaparts.com ($367) and chinaimports.com ($200) for the instrument cluster..

Since I'm primarily interested in the engine hours, I will get a stand alone hour meter from Northern and live with that.

Thanks to everyone.

Steve
 
   / JINMA 204 (2004) Tach wiring ?? #16  
</font><font color="blue" class="small">( Since I'm primarily interested in the engine hours, I will get a stand alone hour meter from Northern and live with that. )</font>
Unless you have no plans whatsoever to use PTO driven implements with that tractor, you might want to rethink that decision.

Most PTO driven implements are designed to be operated most efficiently at one specific RPM. Reving the tractor engine over or under the specified RPM is inefficient, and induces avoidable wear and tear on both engine and implement

//greg//
 
   / JINMA 204 (2004) Tach wiring ??
  • Thread Starter
#17  
Good point Greg.


Steve (also USN ret.)
 
   / JINMA 204 (2004) Tach wiring ?? #18  
Hey Steve have you seen this product TinyTach I am thinking of getting one if I can't get my "short" fixed
 

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