Dealing with voltage regulator on Kohler Command 27?
 

As I continue to work through my SLT1554 to get everything running correctly, I came up with some questions around the voltage regulator.

I replaced the PTO on the tractor (old unit was trashed) and in the install instructions for the new unit, it is explicitly stated that voltage going to the PTO at full throttle needs to be 13.4-14V. So I check at the battery and find 11.4V. Then I move to the voltage regulator:

- 46-47V AC from the stator
- 11.4V DC from the output (B)

Based on what I was able to find, 46-47V AC is ok so I thought I had a bad regulator; about everything else electrical on this thing was bad, so it did not surprise me. I plug a new one in and get some improvement (12V) but no where near 13.4V+.

Now I'm digging around trying to figure out why I'm only getting 12V DC at the regulator output at full throttle when it should be higher. I found several posts across several forum boards that a bad ground may be the problem, or in my case, no ground! Sounds like the body of the regulator should be grounded but there is no wire or strap for mine. I could easily make a wire to run from the regulator screw to the Neg. terminal on the battery, but wanted to make sure this is worth my effort! I would also appreciate it if someone could tell me if the values for the stator are good.

Thanks!

When you measured the voltage.. Did you measure between both AC wires? Or one AC wire to ground?

Also, Are you sure there is a good connection from Battery wire on VR? Sounds like your just reading low battery voltage. I would do all this with a fully charged battery.

MAKE SURE, that the V/R is properly grounded. There should be zero ohms resistance between the V/R case (or housing) and the Battery Negative Terminal ( - ).

I just went out and retested. Battery is fully charged:

- Left AC contact to ground - 48V
- Right AC contact to ground - 0.01V
- Across both AC contacts - 47-48V AC
- B+ to ground - 12.0V DC

Is that right AC contact supposed to be measuring that low? And I have not inspected the battery wire yet. It disappears up under the engine cover and I'm not sure where it comes back out.

Sounds like I need to install a ground wire.

Thanks!

I hope your ground wire fixes it, but I’m doubtful.
That AC is kinda high. But we will see....

I think Terry is correct.. I went online and found the testing procedures.. Easier than typing it all out... Hope this helps.

PROBLEM 1: NO CHARGE TO BATTERY
TEST 1: trace B+ lead from rectifier-regulator to key switch, or other accessible connection. Disconnect it from switch or connection. Connect an ammeter from loose end of B+ lead to positive terminal of battery. Connect DC voltmeter from loose end of B+ lead to negative terminal of battery. With engine running at 3,600 rpm, read voltage on voltmeter.
If voltage is 13.8 volts or more, place a minimum load of 5 amps* on battery to reduce voltage. Observe ammeter.
*NOTE: turn on lights, if 60 watts or more. Or place a 2.5 ohm, 100 watt resistor across battery terminals.
CONCLUSION 1: if voltage is 13.8 to 14.7 and charge rate increases when load is applied, the charging system is okay and battery was fully charged.
If voltage is less than 13.8 or charge rate does not increase when load is applied, test stator (test 2, 3, and 4 below).

TEST 2:Remove connector from rectifier-regulator. With engine running at 3,600 rpm, measure AC voltage across stator leads using an AC voltmeter.
CONCLUSION 2: if voltage is 28 volts or more, stator is okay. Rectifier-regulator is faulty. Replace the rectifier-regulator.
If voltage is less than 28 volts, stator is probably faulty and should be replaced. Test stator further using an ohmmeter (tests 3 & 4 below).

TEST 3: with engine stopped, measure the resistance across stator leads using an ohmmeter.
CONCLUSION 3: if resistance is .064/0.2 ohms, stator is okay.
If resistance is infinite ohms, stator is open. Replace stator.

TEST 4: with engine stopped, measure the resistance from each stator lead to ground using an ohmmeter.
CONCLUSION 4: if resistance is infinite ohms (meaning that there is no continuity), the stator is okay (not shorted to ground).
If resistance (or continuity) is measured, the stator leads are shorted to ground. Replace stator.

NOT the correct way to check the V/R out. See.... https://www.onlycubcadets.net/forum/...read.php?t=368

Per the Service Manual, correct AC Voltage is 28 to 30 VAC. The correct DC Voltage is 13.7 with it no higher than 14.7VDC.

I did not have a ton of time tonight and did not want to fire up the engine but I did try a couple of the tests above:

- I already essentially did Test 2 and get 47-48V. Comments here are that is too high, but the test states that anything above 28V is passing so I'm not sure how to interpret this.

- I performed Test 3 and got 0.1-0.2 ohms on my meter. That seems to be a pass. My meter only reads out to xxx.x, not x.xxx, so I would not be able to read out 0.064. But it definitely was not open line (OL).

- I performed Test 4 on both AC leads and my meter read O.L. As far as I know, that is the same as infinite resistance. If that is true, that test seems to pass.

The link seems to be a graphical explanation of Test 3.

I will redo all of this tomorrow when I have more time, but wanted to get a response back. Tomorrow I'll set up a ground wire, right after I replace a bad fuel line that suddenly started leaking.

Thanks!

If you did test #2 as you stated in the first post of yours I quoted, you are doing it wrong. No wonder you are getting goofy readings. Look at the picture in the link Roland posted. Forget the 5 paragraphs Coop posted. That's a lot of mumbo-jumbo to read. This is an incredibly easy test to perform.

One more thing.... if you disconnect the wire that goes from the R/R to the battery, (center wire) and just try to test the power coming from it, you will get nothing, or whatever nominal battery voltage is. That terminal won't put out anything unless it is connected to a load. See. Didn't take 5 paragraphs to explain that.

Ok, I was sick for several days and a squirrel chewed my fuel line, so I had a couple delays. Installed a new fuel line and was able to continue testing...


So with the connector removed from the VR, and testing each stator wire to ground, I get a stable 19.00V AC from each wire. So it looks like I'm reading very low...

When I test the center connector (battery) to ground, I get 12.36V DC. When I measure the voltage of the battery at the terminals, I get 12.38V DC. This seems to be pretty close.

I installed a new ground wire to the VR, but have not run the engine yet with the VR connector attached (ran out of time).

Thanks!