AC Output Voltage Signal Lost by Controller
What does KOHLER-36 mean?
The KOHLER-36 (Kohler RDC2) diesel fault code means: AC Output Voltage Signal Lost by Controller. This is a serious severity code.
Common Symptoms
- Generator starts and runs but shuts down shortly after and displays code 36 on the RDC2 controller display panel
- Panel shows STOP or fault light after a few seconds of operation even though the engine sounds normal
- No AC power reaches your home circuits even though the engine is running
- ATS does not transfer power to the house loads after the generator starts
- Generator may crank and fire successfully but trips out before reaching full speed
- Weekly exercise cycle starts but ends in a fault shutdown before completing
- Kohler OnCue Plus monitor or RDC2 controller display panel logs a code 36 fault event
Probable Causes (Ranked by Likelihood)
- Blown AC sensing fuse on the generator control board or harness inline fuse Very Likely
- Broken, corroded, or disconnected AC sensing harness wire between alternator output lugs and the RDC2 controller Very Likely
- Faulty or failed AVR circuit preventing AC voltage from reaching sensing input on controller Likely
- Failed alternator output -- stator winding open or shorted so no AC voltage is actually produced Likely
- Damaged or failed RDC2 controller PCB sensing input circuit Possible
- Loose or corroded terminal connection at the alternator output terminal block Possible
- Incorrect voltage sensing leads reversed or miswired after a prior service Less Likely
Step-by-Step Diagnostic Procedure
Set the panel switch to OFF before doing any inspection. Wait for the engine to fully stop and cool for at least two minutes.
Open the control panel cover and locate the AC sensing fuse on the RDC2 controller board or on the sensing harness. Pull the fuse and test it with a multimeter set to continuity. Replace any blown fuse with the exact same amperage rating printed on the original fuse body.
Inspect the AC sensing harness that runs from the alternator output terminal block to the RDC2 controller. Look for chafed insulation, cracked connectors, rodent damage, or any pin that has backed out of its connector housing. Wiggle each connector firmly and reseat it.
Check all terminal connections at the alternator output terminal block. Connections should be tight with no green corrosion or heat discoloration. Torque any loose lugs to the spec in your model's installation manual, typically 35-45 in-lb for smaller residential models.
With the panel switch in AUTO, start the generator manually and use a multimeter set to AC volts on the alternator output terminals. A healthy 60 Hz residential Kohler unit should read 120/240 VAC within about 10 seconds of reaching governed speed at approximately 3600 RPM. If you read 0 VAC at the terminals, the alternator or AVR is the problem, not the sensing wires.
If AC voltage is present at the output terminals but code 36 still trips, the sensing signal is not reaching the RDC2 controller. Trace the sensing leads from the terminal block to the controller board and measure voltage at the controller sense input pins. Presence of voltage there with a continuing fault points to a failed PCB sensing circuit.
If no AC voltage is present at the output terminals, test the AVR by checking for DC excitation voltage from the AVR output to the rotor slip rings. This test requires a service manual for your specific model and is best performed by a certified Kohler technician if you are not comfortable with live AC work.
If you replaced the fuse and reseated all connectors and the fault clears, run the unit through a full exercise cycle and monitor it with the Kohler OnCue Plus monitor or RDC2 controller display panel to confirm the repair held.
Frequently Asked Questions
What does Kohler code 36 mean?
Code 36 means the RDC2 controller is not receiving an AC voltage signal from the alternator output. The controller expects to see 120/240 VAC after the engine reaches governed speed. When that signal is missing or drops out, the controller assumes something is wrong and shuts the unit down to protect your equipment.
Can my generator still run with code 36 active?
No. Code 36 is a shutdown fault. The generator will start and then trip out within seconds. It will not deliver power to your home and the ATS will not transfer your circuits until the fault is cleared.
How much does it cost to fix Kohler code 36?
If the problem is a blown sensing fuse, you can fix it yourself for under $10 and about 20 minutes of work. A damaged harness repair runs $30-$80 in parts and is a moderate DIY job. If the AVR or RDC2 controller board has failed, expect a professional repair bill of $300-$700 depending on parts and your local labor rate.
Will my generator start the next time the power goes out?
Almost certainly not without clearing this fault first. Code 36 places the unit in a hard fault shutdown state. The ATS will signal the generator to start but it will trip the fault again within seconds and your home will stay on utility power or lose power entirely. Clear and repair the fault before the next outage.