Motor not charging Battery - Rectifier??

Rapprunner said:

Good Evening All,
My 1982 60 hp Johnson is no longer charging the battery, I had asked about this another board and I received the following instructions on how to check the rectifier:

"Remove the rectifier wires from the terminal block or unplug it if you don?t have the terminal block. Using a ohm meter (set on RX10K if analog or the diode symbol if digital), connect the black lead of the ohm meter to the rectifier base or black wire if you have one (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.

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.

While you have the rectifier disconnected you can check the charging coils in your stator. Set your meter to the lowest scale possible. Connect a lead to each of the 2 yellow wires coming from the stator. You should get a reading of less than 1 ohm (depending on size of alternator). Now leave one lead connected and connect the other to ground. You should get no reading at all."

Ok did that with the old one - got readings in both directions for both tests. Well I figure it must be bad so I ordered a new rectifier, got it today. Guess what - it too gives readings in both directions for both of the test!

When getting a "reading", I assume that with the ohm meter set as prescribed that that the needle would not move for one test and would move for the other. Is that correct? We were using an analog meter, in one direction the needle would move about 1/4 scale and the other test "pegged" the needle to the max. Is that what one would expect?

I did have another thought after all of this, when removing the old rectifier I noticed that both mounting screws were gone, could that have possibly been the problem by not allowing for a "complete" circuit since I assume that this device is grounded by direct contact with the engine block via the mounting screws within the mounting bracket?

I have not checked the leads from the stator yet, I thought I was onto the problem with the testing and suspected failure of the bad rectifier.

Any advice/help will be greatly appreciated.

Thanks in advance,
Howard V.

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F_R said:

Mounting screws were gone?? You mean it was just dangling around loose in there? Well no wonder it wasn't working. Too bad you didn't consider that before buying a new part.

The test procedure could be better stated as a High and a Low reading. That appears to be what you are getting.

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