New Holland TS90 1998 tachometer problem

[JiiN]

I have problems in my TS90 1998 with tachometer. It works properly in cold but when cabin heat rises up, it often stop working and jam to 0rpm or 700rpm etc. Alternator and tachometer is changed to new one and problem didn't solve with that. I've cleaned alternator's W connector about thousand times. Do You guys have a good hints where and what i should do next to solve this problem?

 

[Agvg]

Bad soldering at the circuit board?

 

[JiiN]

Bad soldering at the circuit board?

Do You mean gauge's circuit board? Tractor had same problem with old tachometer so I changed it to new one.

 

[denchen]

I had a similar problem on a boat years ago. What I put it down as was. The taco W lead as you say, sometimes T, is taken off one of the usually three coils within the alternators AC windings. When you start, the battery will be slightly low, the small wire going to the alternator will tell the voltage regulator to produce current so the inner coils work hard producing a strong AC pulse. As the battery comes up to full voltage, the alternator decreases output, and the AC pulse from the main wiring drops to almost zero, thus giving a week signal to the taco and false readings. This might not sound very scientific, but it seems what happened to my boat. My answer, I bought one of those cheapo Chinese tacos off ebay and epoxy glued a small magnet to the front crank for the sensor. It worked well for years and was still on when I sold the boat. I suppose to test this theory, the next time the taco gives false readings, try switching the lights on full to make the alternator work harder.

 

[RickB]

There are three elements, alternator, tach and wiring harness. You have changed 2. Check the wiring, including the instrument cluster ground and the cab bulkhead connection.

 

[JiiN]

There are three elements, alternator, tach and wiring harness. You have changed 2. Check the wiring, including the instrument cluster ground and the cab bulkhead connection.

That's what i figure too. Does anyone know a color of a wire which gives a signal to tachometer?

 

[JiiN]

I had a similar problem on a boat years ago. What I put it down as was. The taco W lead as you say, sometimes T, is taken off one of the usually three coils within the alternators AC windings. When you start, the battery will be slightly low, the small wire going to the alternator will tell the voltage regulator to produce current so the inner coils work hard producing a strong AC pulse. As the battery comes up to full voltage, the alternator decreases output, and the AC pulse from the main wiring drops to almost zero, thus giving a week signal to the taco and false readings. This might not sound very scientific, but it seems what happened to my boat. My answer, I bought one of those cheapo Chinese tacos off ebay and epoxy glued a small magnet to the front crank for the sensor. It worked well for years and was still on when I sold the boat. I suppose to test this theory, the next time the taco gives false readings, try switching the lights on full to make the alternator work harder.

I've noticed earlier that it doesn't matter is the all lights, heater and radio on. It just stop working when cabin gets warmer, like really hot summer day tacho isn't working almost at all.

 

[JiiN]

And i almost forget to say.. PTO works fine when tacho is having issues to work.

 

[RickB]

And i almost forget to say.. PTO works fine when tacho is having issues to work.

That’s narrows a probable wiring issue to the cluster ground path and the tach signal circuit from thetach to wherever the tach signal is split to feed the tach and the safety circuit.

 

[JiiN]

Does anyone have a wiring diagram? It would be lot easier find the right wire.