Suburban KT30 Furnace 521099 Circuit Board Upgrade: Complete Wiring Fixes & Spark Troubleshooting

Tools & Parts Needed

Find these on Amazon: Digital Multimeter , Wire Strippers , Heat Shrink Tubing Kit

Recognizing the Signs

If you're experiencing this issue, you're not alone. Here's what's typically happening and how to address it.

What You Might Notice

Your Suburban KT30 furnace is only producing one spark instead of continuous sparking because the new circuit board requires proper flame sensor feedback to maintain ignition sequence.

The Underlying Issue

• Improper flame sensor circuit grounding instead of proper connection
• Incompatible electrode assembly with new control board
• Incorrect wiring of the adapter harness
• Missing or incorrect bypass resistor installation
• Faulty connections in the flame sensing circuit

What to Grab

• Multimeter
• Wire strippers
• Electrical tape or heat shrink tubing
• Suburban circuit board manual/wiring diagram for your model
• Small screwdrivers
• Wire nuts or crimp connectors

Working Through It

1. Turn off power and gas supply to the furnace at the main panel and propane tank. Wait 10 minutes for any residual gas to clear before proceeding. WARNING: Never work on gas appliances with power or gas supply connected. Ensure proper ventilation and never use open flames or create sparks near gas connections.
2. Locate the wiring diagram for your circuit board and adapter harness (verify correct part for your model with dealer). This should show the proper flame sensor circuit configuration.
3. Verify power supply voltages to the control board (typically 12VDC and 24VAC) and confirm board LED indicators show normal operation before proceeding with flame sensor circuit work.
4. Disconnect the grounded flame sensor wire that was installed during the initial upgrade. This is likely causing the single-spark issue.
5. Check the electrode assembly to confirm it has integrated flame sensing capability. Most newer electrodes combine spark and flame detection in one unit.
6. Connect the flame sensor circuit properly according to your board specifications. This typically involves connecting to the designated flame sensor terminal (refer to board 521099 manual for specific terminal identification) rather than grounding.
7. If using a flame sensor bypass, install the proper resistor (consult KT30 board 521099 documentation for specific resistance value and part number) or jumper as specified in the board documentation - don't simply ground the wire.
8. Test the connections with a multimeter to ensure proper continuity and resistance values as specified in the manual. Check for proper flame sensor circuit resistance (typically 1-10 kilohms when cold) and verify 24VAC supply voltage to the control board. During operation, verify flame sensor generates proper microamp DC current (typically 0.5-10 microamps) when flame is present.
9. Restore power and gas, then test the furnace operation. You should now get continuous sparking during ignition attempts per manufacturer specifications.

Leave These to the Experts

Contact a certified RV technician if you encounter any of these situations: gas odors during or after the repair, electrical shorts or sparks when connecting wires, continued ignition problems after following these steps, or if you're uncomfortable working with gas appliances. Professional diagnosis may be needed if the new control board or electrode assembly is defective.