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honda bf45a gauge wiring question

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  • honda bf45a gauge wiring question

    aloha everyone, i have a boat with twin 1997 honda bf45a motors, when i recently bought the boat the right side tach and trim gauge was working but on both the back lighting does not work. The left side tach was not working but the trim gauge does and on both the back lights do not work. yesterday i took of the zip ties so i could clearly see both wire harnesses coming from the controls to the gauges. since the right side tach was working, i simply switched the bullet connectors over to the left side tach to see if it would work, it didnt. then when i put the wires back on the left side tach, it stopped working as well. i then removed all the bulbs from all 4 gauges and they all appeared to be in ok condition, no visible broken filaments ect. so i then tested voltage coming from the harness on all 4 sets of connectors leading to the light bulbs and got different results on each set of connectors. 2 had no voltage and 2 had some voltage coming out ( 1 read .08v and the other .03-.04v) none read a full 12v
    i also checked the 2 fuses that are in each harness which had a 10 amp fuse in it and while both the fuses looked like they had corrosion on one end of the metal strip inside the glass housing, when they were removed neither one of the tilt gauges worked when turning on the keys, but after re-installing the fuses, both trim gauges worked. does anyone know if there are additional fuses inside the throttle controller box ? or what voltage i should be seeing coming out of the harness for the gauge back lighting ? i looked all thru my honda 45 service manual, but could not find any info on these topics. i was considering buying one new tach and hooking it up to see if it worked on both sets of wires, but dont want to waste my money. is there any easy way to test the harness or should i test the leads in the control box ? im going to hunt around the back of the boat by the battery's and see if there are any unconnected wires there that might supply the voltage for the gauge backlighting. any and all other suggestions are very welcome. and testing flow chart would also be great if anyone might know the sequence. thank you for all your help. its very much appreciated. aloha

  • #2
    The Red/White wire to gauge is back light and will be connected to either nav light switch in boat or to Black/Yellow wire in instrument harness and should be 12 volts to Red/White with key on or with light switch on.
    Should have 12 volts between Black/Yellow and Black wire at gauges with key on to power up gauges. Gray wire is tach signal from engine and should see voltage increase as rpm's increase on a ac voltmeter.
    Regards
    Boats.net
    Honda Outboard Parts

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    • #3
      thanks for the help. i completely forgot it might be wired to the nav light switch, so will check that. still unsure why tach stopped, mayb it was just its time ? since im getting 12v on the black yellow wire and black for both the gauge, will also check the connections for the gray wire. mahalo aloha

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