How do you test stator on 1990 heritage - FLSTC Heritage Softail Classic Harley Davidson Motorcycles

To check the STATOR. Turn ignition key switch OFF, then disconnect the voltage regulator connector from alternator stator wiring. THEN connect an ohmmeter set on the RX1 scale with one lead into either of the stator sockets and the other lead to a good ground. And test for continuity - a good stator will show no continuity (0 ohms) across either stator socket - any other reading indicates a grounded stator which must be replaced. THEN remove the ground lead and insert lead it into the other stator socket - the resistance (with ohmmeter still set on the RX1 scale)should be 0.1-0.2 ohms - if the resistance is lower a stator short is indicated. Which means that the stator is damaged and must be replaced. - if the resistance is higher (OL on meter), an open is indicated and again, the stator is damaged and must be replaced. You should check socket 1 to 2 then 1 to 3 then 2 to 3. (If you only had a two wire stator you would check between wires/sockets 1 and 2).
Before testing short out the ohmmeter leads against each other and if they do not produce a reading of0 ohms subtract the reading you do get from any readings you get doing the stator checks in order to get accurate stator circuit readings, otherwise you may have out of range reading due to the internal and/or lead resistance of the ohmmeter.

To replace the stator on your bike, you must remove the outer primary cover, remove the compensator sprocket and clutch assembly with the chain. Then you can get access to the stator. You do not have to remove the inner primary on that bike.
Now, the compensator nut torques to 150-165 foot pounds and the mainshaft nut that holds the clutch assembly on torques to 50-60 foot pounds LEFT HANDED.

Good Luck
Steve

sounds like the stator may be grounded

hello and welcome
the alternator per say is split up into several components. the stator coil(located in the left crankcase cover) and the rectifier regulator (which is located bolted onto the frame above the stator area. you can identify this by three yellow wires going into it.
either one can be tested the regulator can be tested at a local dealership. and the stator can be tested by reading an ohm meter between either one of its three wires and ground. if any show up with any continuity between the unplugged yellow wires at the stator and ground the stator is at fault. thank you.