Thermostat clicks, furnace does nothing

2015 travel trailer, Suburban NT-30SP ducted furnace. 30A shore, converter on

Customer says: You turn the heat up, the thermostat clicks, and nothing happens. No fan, no nothing.

Battery at 13.4 V on the converter. The furnace was working last week.

Tests you can run

• Battery voltage
• Furnace fuse at the panel
• Voltage at the furnace on the thermostat wire during a heat call
• Voltage at the blower motor leads during the call
• Amps on the motor lead during the call
• Power off, spin the blower wheel by hand
• Jumper the sail switch
• Replace the control board

Repair options

The lesson behind this case

• The 5-step loop
• Volts, amps and ohms, the simple way

Keep going on furnaces

Learn it

• Furnace sequence
• LP system basics

Prove it

• Furnace blows cold
• Furnace sparks but never lights
• Furnace keeps shutting off, fan keeps blowing
• Comeback: furnace quits again

See it in 3D

• Furnace 3D wiring model

Codes and specs

• Furnace: suburban + atwood/dometic (12v dsi)
• Hydronic heat: aqua-hot 450-de/dm

On the job

• Furnace
• Thermostat