I have a 1991 FLT with bad stator. Stator test reflects short to ground. I am going to replace both stator and regulator with OEM, however would like to test existing regulator to see if still working and I could keep as emergency spare. If I start engine with new stator installed and regulator is bad, will it harm the new stator. I just want to test old regulator and then install new regulator. Thanks!

 

Having a bad regulator shouldn't hurt your stator.

All a regulator does is take the AC power generated by your stator/rotor and turn it into DC power.

 

UNLESS your old regulator is shorted to ground internally, which could blow the new stator.

You could check the resistance to ground (case) on both input lines of the old regulator. Gets complicated with diodes involved and digital multi-meters. But, if you get identical measurements between the old regulator and the new one, you MIGHT be OK. Giving it the smoke test would be definitive. What's the worst that could happen? Blow the new stator? What's the probability? Small. You pays your money and you takes your chances.

 

This would be a safe smoke test for you: Put a 10 amp fuse in line with the old regulator input leads. It would take a bit of creative wiring, including grounding the case, but if it didn't blow the fuse, you'd probably be OK.

 

The first test on an electrical component is to smell it. If it smells burnt then don't even bother.

 

I replaced the stator on my 99 Softail Custom about 3,000 miles ago, and checked the regulator for shorts. Regulator checked out OK, and it has not given any trouble, so I did not replace it. I had replaced it about 14,000 miles back though.

 

There is a procedure for testing the regulator. I got this off of J&P's Cycle site. I did this test when i had my charging problems and ended up putting in a new stator. My old regulator tested good following this procedure and am still running the old regulator. I have added the link to J&P so you have whole test procedure for checking your charging system. Hope this helps. Bully

5. Regulator Test: Each of the following tests isolates the regulator only, so if any of these tests fail, the regulator is at fault.

Identifying Wires:

Battery Charge Lead- Wire going from regulator to battery positive.
AC output leads- Wires coming from the Stator to regulator.
Ground- Wire from Regulator to ground or regulator may be grounded via the physical bolting to chassis.
Regulator Ground Test: Insure the regulator body is grounded or grounding wire is fastened tight to a good ground (you should verify this by checking continuity from regulator body to chassis ground).
Fwd/Reverse Bias Test/Diode Test: This check is testing the Diode function to ensure it is regulating the AC current for the stator into DC Current.
Switch multi meter to Diode Scale.
Place your Multi meter positive lead on each AC output wire.
Place your multi meter negative lead on the battery Charge wire.
The meter should read voltage typically around .5 volts.
Next, switch your multi meter leads putting the negative lead on the AC output wires and the Positive lead on the Battery Charge Wire.
The reading should be Infinite.
With your meter on the same setting, place your multi meter positive lead on the regulator ground wire or to the regulator directly, and then place your meter negative lead on the AC output leads.
The meter should read voltage typically around .5 volts.
Next, switch your multi meter leads putting the negative lead on the regulator ground and the Positive lead on the AC output wires.
The reading should be Infinite.
Note: Below is a table to show the readings:
Positive Lead Negative Lead Reading
AC output 1 Battery charge lead Voltage
AC output 2 Battery Charge Lead Voltage
Battery charge lead AC output 1 ∞
Battery charge lead AC output 2 ∞
Ground AC output 1 Voltage
Ground AC output 2 Voltage
AC output 1 Ground ∞
AC output 2 Ground ∞
http://community.jpcycles.com/articl...g-systems.aspx

 

A quick way to test a regulator is to connect a car battery charger to the inputs (AC stator lines) and the output of the regulator to your battery. The battery should charge at the proper current, as if the charger were connected directly to the battery. Reverse the polarity on the charger (switch plus and minus leads) and it should still charge the same. This indicates the the regulator isn't shorted and won't damage your stator.

As Spanners has said, you still need to measure the charge voltage when it is installed on your bike to make sure the voltage doesn't go above about 15 volts when revving the engine. If the voltage goes much higher your battery will boil and the electronics could be damaged.

 

Why, just throw it in the 10 bushel baskets you have stacked it garage marked electrical..bike..????. You do have them labeled don't you?