markh1
Bronze Member
My tach will start working after my tractor has warmed up but not before. It will continue working if I shut it off and start it again. Any ideas on this?
Mark
Mark
Tach
- Thread starter markh1
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greg_g
Super Member
- Joined
- Dec 18, 2003
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- 6,126
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- Western Kentucky
- Tractor
- JD3720 Cab, 300X loader with 4-in-1 bucket
The tach sending unit is screwed into the side of the bell housing. The tip has an electo-magnetic sensor that counts rotations of the ring gear. If that tip is damaged - or if it's too far away from the ring gear - tach response can be erratic, or not work at all.
To check for tip damage, you must remove it for inspection. Replace if damaged is apparent. If the tip looks undamaged, check for damage to the connecting wires. It may look like only one, but there are actually two wires inside a sleeve. If the wires look good, screw the sender back in slowly - until you feel it barely touch the ring gear. At that point, back it out 1/2 to 3/4 turns and lock back down.
//greg//
To check for tip damage, you must remove it for inspection. Replace if damaged is apparent. If the tip looks undamaged, check for damage to the connecting wires. It may look like only one, but there are actually two wires inside a sleeve. If the wires look good, screw the sender back in slowly - until you feel it barely touch the ring gear. At that point, back it out 1/2 to 3/4 turns and lock back down.
//greg//
greg_g
Super Member
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- Dec 18, 2003
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- 6,126
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- Western Kentucky
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- JD3720 Cab, 300X loader with 4-in-1 bucket
I see yours is a 2003. I'm thinking by then all the Jinmas had changed from individual gauges to cluster gauges. If your sending unit proves good, there have been occasional reports of the tach component of the instrument cluster going bad. But before you write off a cluster, take it out and clean all the multi-blade connectors well - both male and female sides.
//greg//
//greg//
greg_g
Super Member
- Joined
- Dec 18, 2003
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- 6,126
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- Western Kentucky
- Tractor
- JD3720 Cab, 300X loader with 4-in-1 bucket
Sure. Metal expands when heated. If the gap between the sensor tip and the ring gear is marginal, it may close to within tolerance as the metals expand. Same with electrical contacts, like blade or pin connectors and/or solder joints. Some of the most elusive gremlins are those that appear when cold, then disappear when warm.
//greg//
//greg//
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I had the same problem with my tach. The problem was a bad solder joint in the cluster. When the cluster warmed up the wire on the component (in my case a resistor) expanded just enough to make contact and it would worked. The engine warming up had nothing to do with. How I validated this was I would pull the tractor out and let it sit in the sun on a 90 degree day for a couple hours (maybe too late in the year to try this). Every time I let it sit in the sun and the cluster warmed up it worked.
It took me awhile to figure this out.
I do not know enough about your tractor, but I would start with Greg_g suggestions. I would only add, before taking any electrical things apart disconnect the negative side of the battery, to avoid shorting anything out and end up with a bigger problem.
It took me awhile to figure this out.
I do not know enough about your tractor, but I would start with Greg_g suggestions. I would only add, before taking any electrical things apart disconnect the negative side of the battery, to avoid shorting anything out and end up with a bigger problem.
RonMar
Elite Member
Do you have a volt/ohmmeter? The sensor output is approximately 5VAC with the engine running. You can check it at the connection plug located right down by the sensor, forward of the clutch pedal What could be happening is there is a poor connection in the sensor, and as it warms up, it starts to deliver signal...