Should voltage regulator have continuity to its housing?

[Bloke1555]

My Cub Cadet SLT 1550 is blowing the 20A fuse as soon as it is inserted, even with key off and ignition switch unplugged from the back. It reads 12v DC at all times across the fuse box.

The red/white striped wire that leads from the fuse box to the DC alternator has continuity to the frame of the mower, completing the circuit. I tracked it down to the voltage regulator.

The voltage regulator has continuity from its pins to its exterior housing. This seemed wrong, so I bought a new voltage regulator. The new one has the same continuity! Should this be the case? Pic attached.

 

[Richard001]

Bloke,
Welcome to TBN.

If you have the owners manual, there maybe some help there.

Richard

 

[RandyT]

yes you will have a somewhat high resistance reading but you will have continuity to ground because the voltage regulator has to be grounded to close the internal switch to allow battery charging. No ground No charge.

Does it blow the fuse with the regulator unplugged. If no then try a continuity test from one of the stator wires to the engine block and see if you have continuity. If the stator has continuity to ground then it is shorted, and that looks like the Kohler 15 amp regulator, which is a half wave rectifier and the center B+ terminal and the left pin that connects to one of the stator wires is bridged. If the stator is shorted to ground it will feed through the bridged rectifier pins and cause the fuse to blow.

 

[Bloke1555]

The mower does not blow the 20A fuse if the regulator is unscrewed from the engine block (even if wires are still attached).

Which are the stator wires? Should neither of the other two non-fuse-wires leading into the voltage regulator be shorted to ground?

Photo attached, arrow pointing at voltage regulator.

 

[Bloke1555]

None of the three inputs to the voltage regulator is shorted to the engine block, even at X1K ohms. I tested this by removing the regulator and sticking one prong into each exposed port while the other was touching the block. Is one of these the stator wires?

 

[RandyT]

The mower does not blow the 20A fuse if the regulator is unscrewed from the engine block (even if wires are still attached).

Which are the stator wires? Should neither of the other two non-fuse-wires leading into the voltage regulator be shorted to ground?

Photo attached, arrow pointing at voltage regulator.

On Kohler the two outside wires, which should be white are stator wires. They will have low resistance continuity to each other but neither should have continuity to ground. They are basically both ends of the winding from under the flywheel. The center pin is the B+ which should be purple from the battery.

What ohm reading are you getting from the center pin on the rectifier to the metal housing of the rectifier.

 

[Bloke1555]

Center rectifier pin to metal housing of the rectifier is shown in the first picture. Let me know if it's not clear.

 

[Bloke1555]

I've taken some readings.

Old rectifier:
- Center pin to housing, about 28 ohms. One side pin has no continuity to housing while the other has also about 28 ohms.

New rectifier:
- Center pin to housing, about 41 ohms. One side pin has no continuity to housing while the other has also about 41 ohms.

So maybe the new rectifier won't blow my fuse? I still measure 12v across the fuse box when the new rectifier is touching the engine block.

 

[Bloke1555]

I installed the new rectifier and the fuse did not blow. So I guess it was a bad rectifier. But with 12V across the fuse box, won't my battery drain over time?

EDIT: I mowed successfully.

 

[RandyT]

I installed the new rectifier and the fuse did not blow. So I guess it was a bad rectifier. But with 12V across the fuse box, won't my battery drain over time?

EDIT: I mowed successfully.

Can't read the scale on your meter. But it looks like it is set to 1K ohms so are you getting 41 ohms or 41K ohms. If it is working properly the small amount of drain will takes months to drain the battery below a level that will not start

41 ohms is a .3 amp or 300 milliamp draw which is too high. But if it is 41K ohms then .0003 or .3 milliamp would be a normal battery draw. Your car or truck clock pulls more power than that. With a meter that does amps you can remove the negative battery cable set the meter to amps and then connect the red lead to the negative battery cable and the black lead to the negative battery terminal and find what the parasidic draw is providing it is below the protection level of the meter which in most cases is 10 amp fused.