Is tach output voltage from regulator abnormal?

[hkeiner]

I just installed two new CDI voltage regulators on my motor. I replaced my old regulators because their voltage output was too high (over 17V). Also, my tach was not working and I assumed that the tach output (gray send wire) on the regulator was also defective. After replacement, the voltage output is now OK. However, my tach is still not working. My initial conclusion is that the gauge is bad but before I install a new gauge, I want to check that the voltage output from the gray wires (tach send) on the new regulators is according to spec. When I check the gray wire voltage with my Mercury DVA meter (with positive lead on gray wire and negative lead on case ground), I get the following unexpected readings on both regulators:

With engine not running: 12 volts DC and 26 volts AC
With engine running at 800 RPM: 14 volts DC and 17 volts AC

Is it normal to have both an AC and DC voltage reading on the gray tach send wire? Is either the AC or DC voltage too high? How in the heck does one get 26V AC current on the gray tach send wire with the motor off? Does this indicate a defective stator or something else?

I am concerned that the voltage on the gray tach wire is abnormal and may possibly burn out a new tach gauge when I install it. My new fancy tach gauge cost me over $150 so I would hate to damage it so quickly. I am also concerned about damaging my new regulators if the above symptoms are caused by a defective stator.

Any thoughts on this?


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[ricksrster]

Re: Is tach output voltage from regulator abnormal?

Make sure your gray wire ( send ) is connected to a yellow wire at the regulator. Ign is connected to key "on" 12v POS. The Ign wire is usually a Purple wire from the remote control. OF course GRND connects to battery NEG.
You shouldn't be getting a voltage reading with the motor not running. The stator isn't producing electricity is if the fly wheel isn't spinning.

 

[Texasmark]

Re: Is tach output voltage from regulator abnormal?

Rickster, What about backfeed from the battery when the engine is off.....don't have the wiring digram for the regulator to reference.

Mark

 

[hkeiner]

Re: Is tach output voltage from regulator abnormal?

Make sure your gray wire ( send ) is connected to a yellow wire at the regulator. Ign is connected to key "on" 12v POS.

You shouldn't be getting a voltage reading with the motor not running. The stator isn't producing electricity if the fly wheel isn't spinning.

The voltage regulator has a gray wire coming out of it, which is the tach send wire. The tach gauge is connected to this gray wire, which I believe is the correct way to connect the gauge. I am not clear, however, what voltage should be expected at this gray wire when the motor is running and when the motor is not running.

I see from the wiring diagram that the voltage regulator's red wires are connected directly to the battery (via a common connection at the starter solenoid) without the key switch or stator involved. This tells me that the voltage regulator's red wire is always hot (energized) from the battery regardless of key switch position or movement of stator. My guess is that this is causing voltage to exist at the gray wire even when the motor is off. Since both CDI regulators are new and behaving the same way, I initially doubt that they are both defective, unless I know for certain that they should behave differently. I understand that when the stator moves (i.e., engine is running) AC voltage is generated by the stator and flows towards the regulator via the yellow wires for regulated conversion to DC voltage and output thru the red wires to the battery.

In short, can anyone describe how the voltage regulators should behave in regards to AC and/or DC voltage output from the gray wire when the motor is running and when it is not running? And further, whether the readings I describe in my initial post are abnormal or not.

I am confused...

 

[ricksrster]

Re: Is tach output voltage from regulator abnormal?

Rickster, What about backfeed from the battery when the engine is off.....don't have the wiring digram for the regulator to reference.

Mark

I would think the diodes in the regulator would prevent that.