TN75 RPM

[scarlo101]

Good day all,
Yesterday on my TN75 when I started I heard a little bit of a different startup noise. I did not immediately notice anything wrong but later I noticed that I lost my RPM needle & hr meter. Is it common for this to happen? Has something disconnected or did the cable break? How difficult is it to install a new one.
Thanks for your help.

 

[jimglassford]

Well the tachometer is mechanical and the hour meter is electrical so I do not see how the two failures have the same cause.

 

[Roadworthy]

Generally speaking the tachometer and the hour meter are fed from the same source. In older tractors this was a mechanical spinning cable which was not difficult to replace. Sometimes one end would work loose so the cable was no longer spinning the device. Sometimes the cable would break internally. You could just replace the internal drive cable and not necessarily the whole assembly. In many newer tractors both functions are electronic. There may be a pickup on the alternator or elsewhere. Unless you can identify the cable as the driving source for them you should check a service manual or check in with the dealer for possible failures beyond a fuse.

 

[scarlo101]

Thanks for the info, I took a quick look today and I can see what looks like a mechanical cable coming from behind the instrument panel to the mid area of the left side of the engine (drivers side). I will call the dealer to see what is available to purchase.

 

[jimglassford]

Before I replied about the mechanical tach, I did check with the online parts diagram for the TN75 confirming it was mechanical. Before ordering a cable, part number 5197375, make sure it is the cable. It can also be the tach or the gear inside the unit attached to the block.

Now explain why a mechanical tach would also affect the hour meter.

 

[DLTTrekkers]

are electronic. There may be a pickup on the alternator or elsewhere.
It connect to the W point on the alternator.
If the alternator is faulty it will ot work.
Before starting switch it on an check if your bat light and oil light comes on. After starting check if that 2 lights go off .

 

[scarlo101]

Took it apart last week and disassembled it and put it back together and it works fine now. I see there is a 90 degree cable connector from the cable to the back of tack. There seems to be a lot of sloppiness in that area. So the cable is not broken but I suspect it will come back and at that time I will look to see if I can tell where it is getting disconnected.