1973 mercury 1500 charging issues

[rankcummins4x4]

ok so I have a 1973 1500 mercury with thunderbolt ignition motor runs great but its not charging I have checked the rectifier that tested out good. with engine running 1/8 throttle no tach im getting bounicing readings coming from dc side of rectifier is this normal? I do not know how to test stator it has 2 yellow wires on it please help this thing is driving me crazy

 

[racerone]

Test stator with one ohmmeter lead on yellow and one meter lead to ground.----What does it read ?-----One meter lead on yellow and one meter lead on the other yellow.-----What does it read ?

 

[rankcummins4x4]

ok I will check that but is there a dva voltage I need to check to? also is the bouncing voltage on dc red wire from rectifier normal? I see 13.6 to 11.5 it bounces all between those parameters but if I go to battery it reads 12.5 volts

 

[rankcummins4x4]

so from each yellow wire to ground I get no continuity from yellow to yellow I get 0 ohms

 

[Chris1956]

Something may be wrong with your measurements. the yellow stator wires will put out an AC voltage when the motor runs. The rectifier converts that to a DC voltage to charge the battery. The system is unregulated, but the high load of the battery keeps the voltage under control for the most part.

So if you are seeing bouncing voltages at the rectifier, either you have a loose connection to the battery, and you are just seeing battery voltage or the stator is sorta charging. I vote for the former, as the battery usually keeps the charging voltage stable.

Your ohm measurements point to a bad stator, however, if the wiring at the stator is good, the stator is usually good, as it is just a coil. At this age, the wire's insulation usually falls off and grounds the stator, or the copper connector rots away.

I would look for a broken stator wire, where it enters the stator. The stator may be removed after the 8 bolts are removed from the flywheel. Set the motor to TDC, so the flywheel will be easy to re-install.
.

 

[jimmbo]

Have you tried using an Analog Voltmeter? The DC coming out of the Rectifier is not of a Steady Voltage as it is basically a chopped or folded Sine Wave(depending on how many Diodes are in the Rectifier Assembly), no longer alternating from Positive to Negative volts of equal Value, but is now bouncing from Zero to Peak, with no Filtering. As mentioned above, the Battery acts as Filter/Capacitor in these cases. Wet Cell Batteries need to be used with these unregulated Charging systems as the voltage go up as the engine runs faster. AGM Batteries are not suitable for use with these engines.

 

[rankcummins4x4]

ok so I have not tried a analog meter as I don't have one but I picked up a dva adapter to try and does anyone happen to know the output specs on this stator to fully verify the stator is bad or good

 

[Chris1956]

Yes the stator output specs are: Does she charge at 1500 RPM (yes/no)? In no, something (rectifier/wiring/stator) is bad. If she charges, everything is good.

Sorry to be smug....The charging system is real simple.