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jtmurphy1

1486 RPM transducer

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Hi all.  First thanks for letting me be part of this group.  I have been reading a lot of the threads the past month.  I recently bought a 1486 and I believe the rpm transducer is bad.  I read through another post that talked about testing them with ohms, voltage output when the tractor is running, adjusting the depth and have completed those with no fix to the problem. Question.  There are two wires going into the transducer.  Should either of those wires have 12 volt power to it?   Or are both wires an output for the transducer.  Thanks!

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those are not wires that carry any currrent they are strictly for  a magnetic pulse for the data center simiilar to what combines use for shaft monitoring systems remove it and check for magnet damage or loss 

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16 minutes ago, ksfarmdude said:

those are not wires that carry any currrent they are strictly for  a magnetic pulse for the data center simiilar to what combines use for shaft monitoring systems remove it and check for magnet damage or loss 

Magnetic pulse is current.  Low voltage AC current to be exact. 

 

 

The transducer puts out a low voltage AC current which the tach interprets as "on" or "off".  Each time a tooth on the ring gear passes, current spikes, then drops over the valley of the gear.  How fast it switches is read as RPM.  The transmission speed sensor works the same way. 

 

Use a multimeter set to low voltage AC.  With the engine running, put a lead in each wire of the transducer.  Should get a reading.  I do not know the book spec, but if you get nothing, it's bad.  If it jumps all over, it's bad.  Should be a fairly consistent signal. 

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1 minute ago, J-Mech said:

Magnetic pulse is current.  Low voltage AC current to be exact. 

 

 

The transducer puts out a low voltage AC current which the tach interpersonal as "on" or "off".  Each time a tooth on the ring gear passes, current spikes, then drops over the valley of the gear.  How fast it switches is read as RPM.  The transmission speed sensor works the same way. 

Thanks J-mech!!

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I edited my response to include a test.  Please see above post again. 

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I'm not familiar with the 86 series speed sensor. Post a picture if possible. Is this speed transducer the same as a mag-pickup? If so, take it out and wipe the metal particles off the end. Make sure the flywheel hasn't ground it down to the internal wires. To reinstall, center a tooth in the hole. Hand tighten until it touches the tooth then back it out 3/4 of a turn and lock it down. At cranking speed it should produce about 1.5 volts AC. Running could be as low as 3 volts AC or as high as !2 volts AC.

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More shop notes.....

THE RPM SENSOR 130908C2 SHOULD MEASURE <1200 ohm’s AND INCREASE

DECREASE WITH ENGINE RPM’S

THE MPH SENSOR 121869C2 SHOULD MEASURE <1200 ohm’s AND INCREASE/

DECREASE WITH GROUND SPEED

THE EGT SENSOR 130898C2 SHOULD MEASURE 80-100 ohm’s AT ROOM

TEMPERATURE AND 300 ohm’s AT 1200 DEGREES

* SEE SERVICE BULLETIN S-4396

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2 hours ago, CIHTECH said:

More shop notes.....

THE RPM SENSOR 130908C2 SHOULD MEASURE <1200 ohm’s AND INCREASE

DECREASE WITH ENGINE RPM’S

THE MPH SENSOR 121869C2 SHOULD MEASURE <1200 ohm’s AND INCREASE/

DECREASE WITH GROUND SPEED

THE EGT SENSOR 130898C2 SHOULD MEASURE 80-100 ohm’s AT ROOM

TEMPERATURE AND 300 ohm’s AT 1200 DEGREES

* SEE SERVICE BULLETIN S-4396

Thanks CIHTECH!

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28 minutes ago, jtmurphy1 said:

Thanks CIHTECH!

Listen to this advice

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