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Farm Machinery
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1988 JCB 3CX Grey Cab Electronic Tachometer Debug
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<blockquote data-quote="soulman" data-source="post: 7514137" data-attributes="member: 114522"><p>Hi</p><p></p><p>On my JCB 1988 3CX the tachometer, fuel gauge and temp gauge are not working. I have decided to take on this as my next project to fix. On the tachometer side, as i understand it, the alternator has a send terminal (W terminal) that delivers an A/C voltage to the tachometer in the instrument cluster. I noticed that on my machine, there was no wire connected to the W terminal on the alternator and i spotted a loose screened cable not connected to any terminal in the loom feeding the alternator. I believe this screened cable is the tachometer cable. I checked the output voltage of the W terminal using a voltmeter and it read 7 Volts approx. I also did a resistance check between the screened cable and chassis ground and it is giving a very close to short circuit reading so i didn't connect the screened cable to the W terminal until i figure what is causing the potential short circuit.</p><p></p><p>It seems according to the wiring circuit diagram i have, that the alternator terminal is connected to the tachometer directly. Does anyone know if that is actually the case? btw item 33 in wiring diagram is the alternator and item 31 is the speedometer</p><p></p><p>i had a look at the back of the instrument cluster but i cant see straight off, a cable similar to the screened cable down at the alternator. see images attached.</p></blockquote><p></p>
[QUOTE="soulman, post: 7514137, member: 114522"] Hi On my JCB 1988 3CX the tachometer, fuel gauge and temp gauge are not working. I have decided to take on this as my next project to fix. On the tachometer side, as i understand it, the alternator has a send terminal (W terminal) that delivers an A/C voltage to the tachometer in the instrument cluster. I noticed that on my machine, there was no wire connected to the W terminal on the alternator and i spotted a loose screened cable not connected to any terminal in the loom feeding the alternator. I believe this screened cable is the tachometer cable. I checked the output voltage of the W terminal using a voltmeter and it read 7 Volts approx. I also did a resistance check between the screened cable and chassis ground and it is giving a very close to short circuit reading so i didn't connect the screened cable to the W terminal until i figure what is causing the potential short circuit. It seems according to the wiring circuit diagram i have, that the alternator terminal is connected to the tachometer directly. Does anyone know if that is actually the case? btw item 33 in wiring diagram is the alternator and item 31 is the speedometer i had a look at the back of the instrument cluster but i cant see straight off, a cable similar to the screened cable down at the alternator. see images attached. [/QUOTE]
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1988 JCB 3CX Grey Cab Electronic Tachometer Debug
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