Having tach issue

[j_martin]

You can leave the yellow wires where they are, and move the grey tach wire to the other one. It will run fine either place. If there is a voltage regulator wired in, that also could be the problem. (seems to me the crazy regulator, if there is one, hooks up to one yellow wire, and the red wire) On a 9 amp or 16 amp system, you can safely disconnect the regulator altogether for a test. The battery will absorb the extra energy and use it to make bomb gasses out of water.

Leave the tach alone. You said above you substituted another tach and had exactly the same indications.

The rectifier is grounded through mounting screws. I'd take it off and clean under it to be sure it's grounded well.

Lets MAP this. (Maintenance Analysis Procedure)
1. Disconnect the voltage regulator (red and yellow wire going to a small module on top of the motor) if it exists.
a. Problem gone, ----replace voltage regulator
b. Problem persists, leave VR disconnected and proceed
1. Clean the connections and mounting, including the stator ground, If there is not a stator ground wire, take the flywheel off, remove a couple of screws and clean them, or install a wire under one after cleaning the varnish off the stator, 14 g wire, #10 ring eye lug, preferably soldered.
a. problem gone done
b. problem persists
1. swap the grey wire
a. Problem gone --- replace rectifier ---- done
b. Problem persists
1. replace rectifier
a. Problem gone --- rectifier was bad --- done
b. Problem persists--rectifier was good, replace stator.
problem is gone, or something got missed.

If VR is still disconnected, reconnect it.

It is critically important that the steps be taken in order. Each step in the procedure relies on the result of the preceeding step. For instance, you may elect to clean all the connections except the stator ground. If it fixes it, all is good. If it doesn't, the wire swap test is useless until you clean and verify the stator ground first.

This post is what happens when you get an old burned out IBM field engineer involved.

hope it helps
John

[j_martin]

Noticed the comment about the cannon plug. The tach signal ground is through the control set and that cannon plug. Check the ground resistance between the engine block and the negative terminal on the tach. It should be very low, considerably less than 1 ohm.

If the other instruments and the oil alarm work, this is probably OK.

hope it helps
John

[j_martin]

You got me going now.
A wild thought. The vibration of the engine at high RPM might be carressing a connection, such as the instrument circuit fuse in the motor.

John

I gotta go cut some wood. It's gettin' damned cold in MN.

[H2oSki2Fast]

You can leave the yellow wires where they are, and move the grey tach wire to the other one. It will run fine either place. If there is a voltage regulator wired in, that also could be the problem. (seems to me the crazy regulator, if there is one, hooks up to one yellow wire, and the red wire) On a 9 amp or 16 amp system, you can safely disconnect the regulator altogether for a test. The battery will absorb the extra energy and use it to make bomb gasses out of water.

Leave the tach alone. You said above you substituted another tach and had exactly the same indications.

The rectifier is grounded through mounting screws. I'd take it off and clean under it to be sure it's grounded well.

Lets MAP this. (Maintenance Analysis Procedure)
1. Disconnect the voltage regulator (red and yellow wire going to a small module on top of the motor) if it exists.
a. Problem gone, ----replace voltage regulator
b. Problem persists, leave VR disconnected and proceed
1. Clean the connections and mounting, including the stator ground, If there is not a stator ground wire, take the flywheel off, remove a couple of screws and clean them, or install a wire under one after cleaning the varnish off the stator, 14 g wire, #10 ring eye lug, preferably soldered.
a. problem gone done
b. problem persists
1. swap the grey wire
a. Problem gone --- replace rectifier ---- done
b. Problem persists
1. replace rectifier
a. Problem gone --- rectifier was bad --- done
b. Problem persists--rectifier was good, replace stator.
problem is gone, or something got missed.

If VR is still disconnected, reconnect it.

It is critically important that the steps be taken in order. Each step in the procedure relies on the result of the preceeding step. For instance, you may elect to clean all the connections except the stator ground. If it fixes it, all is good. If it doesn't, the wire swap test is useless until you clean and verify the stator ground first.

This post is what happens when you get an old burned out IBM field engineer involved.

hope it helps
John

Thanks for the break down. I didn't have time to get a new rectifier, but I did swap the tach wire to the other position, and the problem got worse (tach started floating around at just under 4500 rpm). Also, the rectifier looked burnt so I am guessing thats where the problem is. The next time I got out (probably over X-mas), I'll put a new rectifier on it and if that doesn't work....... I'll use your flow chart.

[WATERWINGS]

I swapped out the bouncing Gaffrig yesterday with a Merc 6000 R' tach.

The bouncing went away.......so it must be the tach.

I had to bypass the Summit Tach Recall to make the Merc tach work at all.

But when I bypassed the recall, the Merc tach worked just fine, with no bounce at all.

Now I guess the Tach Recall may have something to do with the bounce, but untill I send the Gaffrig off, and get it re-worked, I wont know for sure.


It sure is tough when you can't see the rest of your RPM's though.