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2003 Johnson 90 intermittant charging & Tach

newbernbuck

New member
New to this group, thanks to everyone.

I have a 2003 Johnson 90 2 stroke J90PLSTC. Last season I replaced a faulty volt regulator with a CDI 193-6048 unit. All fine last season. But this year both charging and tach are randomly intermittent. Engine runs fine. Some times it's not charging at all, then charging around 14V, then jumps to 17.5V sometimes all within a few minutes of each other confirmed with DVM. The tach may not work at all for awhile then it's fine and may jump around as well, with no relation as to what the voltmeter says. Sometimes everything may be perfect for several hours.

I have rechecked every connection I can think of including battery connections and a new battery. Is it possible the ignition switch could be at fault? Stator?

I went to Johnson outboard school back in 1977, but I'm afraid my handyman skills are not what they used to be.
Any advice if appreciated.
 
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(Testing Tachometer With Water Cooled Regulator/Rectifier)
(J. Reeves)

A quick check is to simply plug in a another new tachometer as a piece of test equipment. If the new tach works properly and the old tach didn't, obviously the old tach is faulty.... but usually boaters don't carry around a spare tach (see below).

A faulty rectifier wouldn't damage the tachometer, the tachometer simply wouldn't work. This is due to the fact that the tachometer operates off of the charging system and the rectifier converts AC voltage to DC voltage, enabling the charging system. A faulty rectifier disables the charging system, and the tachometer simply doesn't register.

However.... those water cooled regulator/rectifiers that are used on the 35 ampere charging systems (and some others) bring into play a different type problem, and as you've probably found out, they are really a pain to troubleshoot via the proper procedure. There's an easier way.

The tachometer sending/receiving setup operates off of the gray wire at the tachometer. That same gray wire exists at the engine wiring harness which is connected to the engine electrical terminal strip. You'll see that there is a gray wire leading from the regulator/rectifier to that terminal strip, and that there is another gray wire attached to it. That other gray wire is the wire leading to the tachometer which is the one you're looking for.

NOTE: For the later models that DO NOT incorporate a wiring terminal strip, splicing into the "Yellow Wire" mentioned will be necessary.

Normally the Gray wire leading from the tachometer is attached at the terminal strip to another Gray wire which leads from the water cooled voltage regulator/rectifier...... remove the gray wire that leads to the tachometer. Now, find the two (2) yellow wires leading from the stator to that terminal strip. Hopefully one of them is either yellow/gray or is connected to a yellow/gray wire at the terminal strip. If so, connect the gray wire you removed previously to that yellow/gray terminal. Start the engine and check the tachometers operation, and if the tachometer operates as it should, then the regulator/rectifier is faulty and will require replacing. If the tachometer is still faulty, replace the tachometer.

If neither of the yellow wires from the stator is yellow/gray, and neither is attached to a yellow/gray wire, then attach that gray tachometer wire to either yellow stator wire, then the other yellow wire, checking the tachometer operation on both connections.

I've found this method to be a quick and efficient way of finding out which component is faulty.... the tachometer or the regulator/rectifier. It sounds drawn out but really only takes a very short time to run through. If the water cooled regulator/rectifier proves to be faulty, don't put off replacing it as they have been known to catch on fire with disastrous consequences.
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Since both charging (sometimes not charging, then charging, then overcharging 17+V) and tach operation is intermittent as well, maybe I'll try disconnecting the tach altogether and see then if the charging is affected when out on the water.
Thanks to all.
 
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