Re: 1998 johnson 88 tach trouble
You (original poster) or someone stated in the above 2nd post (copy/paste):
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"Just FYI there are two sets of tachometer wires coming off the engine harness. One set is in the cannon plug for the system check tach. However there is another set of wires (purple, grey and black) that is in the bundle. someone used the power and ground out of that set to power dash lights, however they also connected the grey wire to the ground for the lights which grounded out the tach signal. Make sure if you use the cannon plug you do not hook up the sencond grey signal wire!
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Having the tachometer Gray "sensor" wire grounded is an excellent way to blow that new rectifier. I strongly suggest that you disconnect that dash light wiring method and wire those lights correctly via separate wiring from the battery to a fuse panal, then to whatever accessory you need 12 volts applied to independently of the ignition switch. The "gray" wire has continuity to all other "gray" wires on that engine's circuitry regardless of what location they may be located.... the same holds true for all other colored coded wires
Should you be using the small three (3) wire rectifier on that engine, disconnect the three wires and test it as follows.
(Small Rectifier Description & Location)
(J. Reeves)
On most 2,3,4,6 cylinder engines, the small rectifier is located on the starboard (right) side of the engine just in front of the engines electrical wiring strip. There are a few older V4 engines that have the wiring strip on the rear portion of the engine and the rectifier would be located just under that terminal strip. The smaller horsepower engines usually have the rectifier located on the starboard side of the powerhead close to the carburetor area.
The rectifier appears to be a round object approximately one inch (1") in diameter and also about one inch (1") high. The base of it is sort of triangular in appearance and is attached to the engine with two (2) screws/bolts..... usually one screw/bolt is larger than the other. The rectifier, depending on which one your engine uses, will have either:
One Red wire, one Yellow wire, and one Yellow/Gray wire, or One Red wire, and two Yellow wires.
Note that either of the above rectifiers could have a fourth wire which would be Yellow/Blue
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(Small Rectifier Test)
(J. Reeves)
Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.
Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.
Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.
Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.
Now, with either of those engine wiring harness tachometer leads (Black, Gray, Purple) attached to nothing, and having a known good rectifier....... Connect the harness Purple wire to the purple tach wire (12v), connect the harness Black wire to the black tach wire (- ground), connect the harness Gray wire to the gray tachometer wire (Sensor).
With 12v being applied to the tachometer only when the key is turned to the Run position, the tach needle should peg down to zero. Let us know what you find.
