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post #1 of 3 (permalink) Old 03-16-09, 05:57 PM Thread Starter
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Question Tachometer Only Works Sometimes

1997 F250 Super Duty 5.8L Gas Engine. My Tachometer only works once in a while. Everything else seems OK. I understand the signal for the tach comes from the PCM anyone which pins/wires, and where does it connect to the tach.

Only other problem with truck is the lights go bright then dim, kinda surging. I think that must be the alternator although the voltage seems fine when I check it with a DVM.

Any help would be greatly appreciated!

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post #2 of 3 (permalink) Old 03-17-09, 12:54 AM
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Re: Tachometer Only Works Sometimes

Sound Like A Voltage Regulator On The Rear Of The Alt
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post #3 of 3 (permalink) Old 07-06-09, 12:04 PM
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Re: Tachometer Only Works Sometimes

The problem is in the instrument cluster. If you remove the cluster there will be a flat cable plugged into a single line square pin header. This will be on the back of the area where the display is. If you unplug the board you will find that there will be a solder joint that has a crack surrounding the pin. It is most likely the pin that is separated from the rest by a missing pin. Heat and reflow the solder on this pin and your problem will be solved.
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