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Thread: no tach on mfd

  1. #1
    Lake Mead Bum & BTLS Mark starflight's Avatar
    Join Date
    May 2007
    Boulder City, NV

    no tach on mfd

    Hey guys. I need help. I've ohm'd out the yellow from elec box to mfd, and the wire is good. I ohm'd out the yel to red/purp and get .6 ohms. Besides the mfd is there anything else that can keep it from dispalying the rpm? Mfd will not wake up if I start the engine, and displays 0 rpm when running when I wake it. All other functions work. Bad mfd?
    The system charges the battery just fine.

  2. #2

    Join Date
    Jun 2007
    California, MD
    Looking at the schematic, you should be able to test from the positive battery cable to the yellow wire at the MFD and read .6 ohms. (This path begins at the POS batt cable to the to the starter solenoid to the Circuit breaker to the stator to the junction inside the box to the MFD connector). The segments you tested seem good, but are they testing the connections inside the box? If the complete path is good, and all other functions work, then yes you're probably looking at a bad MFD.

    Sounds like a good candidate for Feral...he was looking to start an MFD repair service for us GH Polaris folks.

  3. #3
    Wankel till I die!! jonjonwells's Avatar
    Join Date
    Apr 2007
    SE Kansas
    Mine did this to me about a year ago. Figured it was cheaper to go with a tinytach. My fuel side of the MFD fried as well. Hopefully yours will continue to work. No fuel guage sucks.

  4. #4
    Lake Mead Bum & BTLS Mark starflight's Avatar
    Join Date
    May 2007
    Boulder City, NV
    Thanks for the info guys. If I get an aftermarket tach, I'd like to get a gps/ tach combo unit. Been thinking about the water proof tach that Randy sells also, but check this out...

    If it can be used w/ outboards (doesn't say 2 stroke though), you think it can be used for a 3 cyl engine? It say that if a capacitive discharge ign. system is used, you must use the tach out on the cdi. The cdi doesn't have that, but do you think the signal from the yellow on the stator will do the trick? It says not to use the ign. coil for the signal if its connected to a cdi system, such as msd. Think it may work?

  5. #5
    Moderator beerdart's Avatar
    Join Date
    Aug 2006
    Go with the PET 2100DX it updates 20 times per sec and holds max RPM.. Uses inductive pickup..

  6. #6
    2000 pro 785 (son's) 1998 pro 785 (dads) old guy in mich's Avatar
    Join Date
    Aug 2007
    sw lower mich
    MFD Troubleshooting/Reset
    Never replace the 1/4 amp fuse with one of a higher rating. You will cause irreparable damage to the MFD if something goes wrong.

    Power surges or spikes are the most common cause for a blown fuse.
    The power surges can be caused by loose connections in the electrical box (remove and re-crimp all connectors, I'd also replace the board as it's so inexpensive). Poor ground at the engine plate (scrape off the paint and clean the connector), even corroded or loose battery connections will cause this issue (remove and clean the connections).
    Anytime the charging path is interupted there's a potential for a voltage spike.
    I think 14.1 is to much charging output, check the actual value with a "GOOD" meter (Fluke comes to mind) and make sure of the voltage being charged to the battery.
    When you split the box, it's also not a bad idea to replace the voltage regulator.

    While on the subject of MFD's and LOPr.

    The LOPr will only come on when the battery voltage is under 10.9
    Remember power fluctuations (usually caused by loose connections) or electrical noise caused by the ignition system may cause the MFD to lose voltage calibration data. These "events" will also show LOPr.

    Check and correct the charging system, battery, battery connections, fuse connections, MFD pin connectors, (pay peticular attention to power and ground connections at the MFD).

    To re-set the MFD
    Press and hold the MODE and SET keys until the CAL displays. The CAL display will usually show after 4 seconds
    Press and hold the SET key
    While continuing to hold the SET key ans within 2 seconds of pressing the SET key, press and hold the MODE key
    Don't release either key until the MFD shuts down
    After the MFD has shut itself down, press the mode key to turn the MFD on
    Depress the MODE key repeatedly until voltage is displayed and verify that the voltage reading has been restored.

    Display is stuck one one function/display shows all 8's/buttons don't work

    This malfuntion can occur when the battery has been disconnected or removed.
    It may freeze on any funtion, or with all 8's the MFD is running its self check during power up.
    This will usually happen when there is a power glitch and the micro-processor temorarily malfunctions.
    It will usually correct itself when you disconnect the battery for a few minutes, it usually takes 2-3 minutes to re-set the micro-processor.

    When connecting the battery negative cable, make sure it is a "clean connection. Meaning only let the terminal contact the battery once. DON'T repeatedly contact the battery!! Hold pressure on the cable until the bolt is tight.

    If you have problems connecting the battery terminals you can disconnect the MFD, install the cables and then plug the MFD back in (my recomendation).

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