NX5010 tach not working

[PMJG207]

First time posting here on TBN.

I致e been having issues with my NX5010. The Tach had kind of been on and off the past year or so. No it just won稚 work. It seems to try and do the sweep at start up but only moves 1/8 or so. I tested both ground connections on the é„* dash plug. Everything was good 0 ohms to ground. I致e done the remove the negative terminal for ten mins to get rid of the 渡oise?

Looking through the schematics I see that the alternator pulse signal goes to both the safety controller and the HST controller. I do not see where it goes to the dash. The dash plug has no wire at pin A25 �ach pulse input?

I have checked all the fuses as well. Everything else works on the dash and all the lights work. Any help is greatly appreciated.

 

[TN8Man]

Check the tach pickup sensor. It sends out a square-wave (0-12V) where the frequency is translated into RPM. A oscilloscope could verify the signal.

 

[PMJG207]

Yea that is my next step is to make sure the alternator is putting out a square wave. Sadly I do not access to an O scope. I should be able to see it change with the frequency setting on my multimeter correct? Also does the temp gauge do a sweep normally at start up?

 

[justman777]

If I recall correctly, all the gauges do a full sweep at startup on my 2018 NX4510. Regarding the frequency setting on your DMM, I think it depends on your DMM. Give it a whirl and let us know what you find. If nothing else, it'll help the next guy who has the same issue.

 

[TN8Man]

Yea that is my next step is to make sure the alternator is putting out a square wave. Sadly I do not access to an O scope. I should be able to see it change with the frequency setting on my multimeter correct? Also does the temp gauge do a sweep normally at start up?

The frequency will be 481Hz at 850 rpm, 566Hz at 1000 rpm, 1133Hz at 2000 rpm and 1700Hz at 3000 rpm. A dvm without a frequency counter will not work but you might be able to measure the average DC voltage of around 6.5V

The pickup sensor might have come loose from the engine gear case.

 

[Kioti Dave]

Yes, all gages do full sweep.

 

[PMJG207]

Here is what I came up with today. I unplugged the pulse output on the alternator and plugged in the multimeter. With it on the frequency setting and started the tractor. Not sure if it was my two year old hitting the tires with his snow shovel or me finally asking for help on here but all the gauges did a full sweep and the Tach was working reading just about 1000rpm. I was reading 170Hz on the dmm at idle. Doing the math.

Alternator pully diameter - 70mm
Balancer is about 110mm
12 pole alternator

170=(12/2)x(rpm/60)
1700rpm for the alternator

1700x0.64(pully ratio)= 1088 engine rpm

I didnt get a chance to hook into the crank sensor. Seeing as with the alternator pulse signal removed the tach still worked tells me that it is using the crank sensor for the tach not the pulse signal as the workshop manual says. I am guessing the tach signal is sent to the dash via the can bus rather then the individual pin A25.

 

[PMJG207]

I forgot to respond with the conclusion once I got it working again. (slightly preoccupied with the birth of my second child.) I'm still not 100% sure but it seems to be a loose connection the instrument cluster plug. I had it happen again about two weeks ago. The tach, hour meter and temp gauge stop working but all came back when I unplugged the instrument cluster and re installed. All connections seem to be in good shape.