Tach quit working today - Printable Version

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+--- Thread: Tach quit working today (/showthread.php?tid=3837)

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Tach quit working today - pestes - 10-27-2017

Drove out of Shendoah River State Park this morning and noticed right away that my tach was bouncing back and forth between 0 and max with "test" on the LCD display just like it normally does when I start the engine. Except it literally did this all day long. Tach is correct on the VMSpc so I suspect something between dash and rear. It worked when we pulled in 5 days prior. Of note, I did have the dash off when parked for the week to mount the VMSpc tablet but I never had my hands anywhere near the instrument cluster. Does the tach connect all the way to the rear? Or does it go to the Allison computer under the driver?

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RE: Tach quit working today - 77newell - 11-01-2017

On my 93 coach, both the engine and transmission ECU put out a signal that could be used by the speedometer. I believe mine comes from the transmission. Given the changes between the making of our models I would be inclined to ask the factory what source they used when yours was made. It probably will still be from the transmission ECU, but given the way the newer ECUs talk to each other anything is possible.

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