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No more system check/warning horn

J

jshane37

Regular Contributor
Ok this is going to be one of those questions that may have 1000 different answers but here goes anyway! 99 225 Johnson. I went from 2 weeks ago system check with lights checking down in proper order and chirp with warning horn. 1 week ago no lights on system check gauge but a faint to loud warning horn steady, to a few days ago no warning horn or system check lights. I believe I have gremlins running amok! Anyone have suggestions where to start with this one? Ground? Power? Bad Tach? Bad Horn?
Side bar.....I have also lost my tilt/trim gauge....no power to it that is.....gauge does not respond.
 
Sounds like a loose or corroded connection some where in the boat wiring harness or a bad tach. Check all the connections first.
 
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I pulled the instrument panel and the connections on the engine and checked with a fine toothed comb and found nada. Even check the wires in to the warning horn and subsequent connections for moisture and or corrosion and again...nada. I am totally puzzled.
 
Boobie is right. Check it again. Look for +12v on the purple wire at tach and horn and TT gauge. WITH KEY ON. Make sure all grounds are good. Bypass the ground with a known good wire to a known good ground if you have to.
 
Thanks Doug. Just got back from playing around with it and here is what I discovered. I was able to activate the horn by jumping a negative wire to the tan and purple wire. However....I still get no check down lights on the gauge and still nothing on the horn with normal key activation. Ideas? Probably un-related but I still have no power to the tilt gauge. I am showing 13+ with volts so I am getting good pos.
 
Anyone have a diagram on where the ground may be for the horn/tach and where the horn wire ties into the cylinder head area?
 
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Horn wire does not tie into cyl head area.
Look at the electrical connections on the port side behind that small panel. You will see three large deutsch connectors that connect the boat side harness to the engine harness. Note the colors of the wires. One of the connectors has purple, black, red, etc. (multi colors), and that one is the connector that runs to your key switch. Sorry, I don't remember all the colors off the top of my head. It will have wires for ground, +12v, switched +12v, primer solenoid, starter solenoid, and kill wire.

The other connector is almost exclusively tan wires with stripes. Tan, tan/yellow, tan/black, etc. That connector is for your warning horn system. These wires feed directly into the back of the systems check tach. The tach then controls the warning horn on that tan/blue(?) wire that you say you have already grounded for horn testing.

So, the circuit at the horn is purple(+12), ground, and the tan/blue(?) signal wire. When that tan/blue wire goes to ground, the horn sounds. The tach drives it to ground when the tach senses one of those other tan lines coming from the engine has triggered (switched to ground).

The whole system works based on the concept of these sensors switching to ground when the fault is present. Overtemp, the sensor in the head will switch to ground. Fuel restriction, the vacuum switch right there at the fuel pump will switch to ground. No oil, the tan/??? line coming from the OMS fuel pump will switch to ground. ETC. The tach knows which line is active, turns on the appropriate light, and sounds the horn.

You can test all these systems by simply groundiing the tan wire at each sensor, with key on, and watching the lights on the tach. The horn will NOT SOUND when testing in this manner UNLESS THE ENGINE IS RUNNING.
 
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