Tachometer Trouble repost

[john Thomason]

" Joe---I posted a question fo

" Joe---I posted a question for you under the wrong heading, concerning the malfunction of a faria tachometer. I sent the tachometer back for replacement and the replacement doesn't work either. As I stated in my first post, this is a new application. I talked with an elderly gentalman (retired) and he stated that the tachometer works of A.C. current and that a test light will blink when hooked to the sensor wire, with the motor running. Mine DOES. Would you say this Tachometer is not designed for my 40 Johnson 1985 model or have I got TWO defective Tachometers? "

 

[joereeves]

"John.... Without actually bei

"John.... Without actually being there, it's difficult to make a judgement call on your problem. However, in order for a tachometer to operate with a OMC engine, the tach must operate off of the charging (alternator) system, and the OMC charging alternating system puts out a 6 pulse signal. The tach must be set to accept this 6 pulse signal..... Usually via a dial on the back of the tach.

If your engine has a alternating charging system, there will be a rectifier attached to the engine with 2 screws. This rectifier has a 1" round section, with a triangular base and has three (and sometimes four) wires leading from it to a terminal board.

These wires are "yellow", "yellow/gray", and "red". If a 4th wire exists, it will be "yellow/blue". The "yellow/gray" wire terminal is the one that another gray wire would be attached to which leads to the tachometer gray wire (pulse connection).

If the rectifier exists, your engine has a alternator charging system. However, the rectifier may be faulty and can be checked as follows. (Sorry if we've been through this before but I didn't check the prior posts).

(Small Rectifier Test)

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 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.

Joe

"

 

[joereeves]

Just checked that older post.

Just checked that older post..... seems like we covered that rectifier bit.

Joe

 

[john Thomason]

" Joe---I finally got the tach

" Joe---I finally got the tachometer working, don't know what I did, it just started working. Now I have two final Question. The tachometer does not seem to be accurate. It is hard to describe, so I want attempt to do so. I have both the new tack. and the replacement the company sent me. They both act the same. ALL wireing has been checked and double checked. The Faria tach. instructions say to connect the sensor wire of the tach. to the UN-RECTIFIED wire from the stator. The pulse setting is set as specified. My rectifier has three yellow wires and one red wire. The yellow-grey wire from the stator , the yellow-grey wire from the rectifier and the grey tach. wire are all connected to the sane terminal post. I have connected the tach, as the instructions stated, to the yellow-grey wire from the stator(without the rectifier wire) and the tach. worked basically the same. The rectifier, as I stated in the other post, checked ok. My questions are: (1) Should all three wires be connected together? (2) A new rectifier is about $45.00, could my problem be in the rectifier. I am well aware that some electrical problems can be a nightmare for even the best technicians. It just takes time to find. THANKS for all your help ! "

 

[joereeves]

"John... If the tach works, th

"John... If the tach works, the rectifier is okay. The three wires...rectifier yellow/gray, stator yellow/gray, and the gray wire should all be together. If the tach reads wrong, I could only assume that it is not set for 6 pulses.

Joe

"